前言
RecyclerView的侧滑功能主要是通过ItemTouchHelper这个类来完成的
这个类在androidx和support库里面都有
这里我们主要是手动拷贝一份，来讲解所有关键代码的实现思路
在阅读时，没必要每行代码都弄懂，那是不太现实的
关键是能读懂关键代码，能对自己想要的地方进行改动
实现思路
核心代码
//这个控件的拖拽还有BUG，有时交换元素时，元素会消失
//主要通过Demo来读源码流程，细节上不要太较真
@SuppressWarnings("all")
public class ItemTouchHelper extends RecyclerView.ItemDecoration implements RecyclerView.OnChildAttachStateChangeListener {
/**
* Up direction, used for swipe & drag control.
*/
public static final int UP = 1;
/**
* Down direction, used for swipe & drag control.
*/
public static final int DOWN = 1 << 1;
/**
* Left direction, used for swipe & drag control.
*/
public static final int LEFT = 1 << 2;
/**
* Right direction, used for swipe & drag control.
*/
public static final int RIGHT = 1 << 3;
// If you change these relative direction values, update Callback#convertToAbsoluteDirection,
// Callback#convertToRelativeDirection.
/**
* Horizontal start direction. Resolved to LEFT or RIGHT depending on RecyclerView's layout
* direction. Used for swipe & drag control.
*/
public static final int START = LEFT << 2;
/**
* Horizontal end direction. Resolved to LEFT or RIGHT depending on RecyclerView's layout
* direction. Used for swipe & drag control.
*/
public static final int END = RIGHT << 2;
/**
* ItemTouchHelper is in idle state. At this state, either there is no related motion event by
* the user or latest motion events have not yet triggered a swipe or drag.
*/
public static final int ACTION_STATE_IDLE = 0;
/**
* A View is currently being swiped.
*/
public static final int ACTION_STATE_SWIPE = 1;
/**
* A View is currently being dragged.
*/
public static final int ACTION_STATE_DRAG = 2;
/**
* Animation type for views which are swiped successfully.
*/
public static final int ANIMATION_TYPE_SWIPE_SUCCESS = 1 << 1;
/**
* Animation type for views which are not completely swiped thus will animate back to their
* original position.
*/
public static final int ANIMATION_TYPE_SWIPE_CANCEL = 1 << 2;
/**
* Animation type for views that were dragged and now will animate to their final position.
*/
public static final int ANIMATION_TYPE_DRAG = 1 << 3;
static final int ACTIVE_POINTER_ID_NONE = -1;
static final int DIRECTION_FLAG_COUNT = 8;
private static final int ACTION_MODE_IDLE_MASK = (1 << DIRECTION_FLAG_COUNT) - 1;
static final int ACTION_MODE_SWIPE_MASK = ACTION_MODE_IDLE_MASK << DIRECTION_FLAG_COUNT;
static final int ACTION_MODE_DRAG_MASK = ACTION_MODE_SWIPE_MASK << DIRECTION_FLAG_COUNT;
/**
* The unit we are using to track velocity
*/
private static final int PIXELS_PER_SECOND = 1000;
/**
* Views, whose state should be cleared after they are detached from RecyclerView.
* This is necessary after swipe dismissing an item. We wait until animator finishes its job
* to clean these views.
*/
final List<View> mPendingCleanup = new ArrayList<View>();
/**
* Re-use array to calculate dx dy for a ViewHolder
*/
private final float[] mTmpPosition = new float[2];
/**
* Currently selected view holder
*/
ViewHolder mSelected = null;
ViewHolder mPreOpened = null;
/**
* The reference coordinates for the action start. For drag & drop, this is the time long
* press is completed vs for swipe, this is the initial touch point.
*/
float mInitialTouchX;
float mInitialTouchY;
/**
* Set when ItemTouchHelper is assigned to a RecyclerView.
*/
float mSwipeEscapeVelocity;
/**
* Set when ItemTouchHelper is assigned to a RecyclerView.
*/
float mMaxSwipeVelocity;
/**
* The diff between the last event and initial touch.
*/
float mDx;
float mDy;
/**
* The coordinates of the selected view at the time it is selected. We record these values
* when action starts so that we can consistently position it even if LayoutManager moves the
* View.
*/
float mSelectedStartX;
float mSelectedStartY;
/**
* The pointer we are tracking.
*/
int mActivePointerId = ACTIVE_POINTER_ID_NONE;
/**
* Developer callback which controls the behavior of ItemTouchHelper.
*/
Callback mCallback;
/**
* Current mode.
*/
int mActionState = ACTION_STATE_IDLE;
/**
* The direction flags obtained from unmasking
* {@link Callback#getAbsoluteMovementFlags(RecyclerView, ViewHolder)} for the current
* action state.
*/
int mSelectedFlags;
/**
* When a View is dragged or swiped and needs to go back to where it was, we create a Recover
* Animation and animate it to its location using this custom Animator, instead of using
* framework Animators.
* Using framework animators has the side effect of clashing with ItemAnimator, creating
* jumpy UIs.
*/
List<RecoverAnimation> mRecoverAnimations = new ArrayList<RecoverAnimation>();
private int mSlop;
RecyclerView mRecyclerView;
/**
* When user drags a view to the edge, we start scrolling the LayoutManager as long as View
* is partially out of bounds.
*/
//REMARK => 手指移到控件以外时，仍然继续拖拽
//这只是个细节功能，没有也不影响控件使用
final Runnable mScrollRunnable = new Runnable() {
@Override
public void run() {
// if (mSelected != null && scrollIfNecessary()) {
// if (mSelected != null) { //it might be lost during scrolling
// moveIfNecessary(mSelected);
// }
// mRecyclerView.removeCallbacks(mScrollRunnable);
// ViewCompat.postOnAnimation(mRecyclerView, this);
// }
}
};
/**
* Used for detecting fling swipe
*/
VelocityTracker mVelocityTracker;
//re-used list for selecting a swap target
private List<ViewHolder> mSwapTargets;
//re used for for sorting swap targets
private List<Integer> mDistances;
/**
* If drag & drop is supported, we use child drawing order to bring them to front.
*/
private RecyclerView.ChildDrawingOrderCallback mChildDrawingOrderCallback = null;
/**
* This keeps a reference to the child dragged by the user. Even after user stops dragging,
* until view reaches its final position (end of recover animation), we keep a reference so
* that it can be drawn above other children.
*/
View mOverdrawChild = null;
/**
* We cache the position of the overdraw child to avoid recalculating it each time child
* position callback is called. This value is invalidated whenever a child is attached or
* detached.
*/
int mOverdrawChildPosition = -1;
/**
* Used to detect long press.
*/
GestureDetectorCompat mGestureDetector;
/**
* Callback for when long press occurs.
*/
ItemTouchHelperGestureListener mItemTouchHelperGestureListener;
final OnItemTouchListener mOnItemTouchListener = new OnItemTouchListener() {
boolean mClick = false;
float initX = 0F;
//REMARK => 这个方法主要处理两件事情
//一个是在Item进入滑动状态前，判断用户要进行何种操作，这个主要是通过checkSelectForSwipe方法完成的
//二是当Item已经被选中时，单击可以取消选中状态，这个主要是通过endRecoverAnimation方法来完成的
@Override
public boolean onInterceptTouchEvent(RecyclerView recyclerView, MotionEvent e) {
Console.debug("OnItemTouchListener.onInterceptTouchEvent");
mGestureDetector.onTouchEvent(e);
final int action = e.getActionMasked();
if (action == MotionEvent.ACTION_DOWN) {
mClick = true;
mActivePointerId = e.getPointerId(0);
mInitialTouchX = e.getX();
//用来做判断
initX = e.getX();
mInitialTouchY = e.getY();
obtainVelocityTracker();
if (mSelected == null) {
final RecoverAnimation animation = findAnimation(e);
if (animation != null) { //找出还在进行的动画
//REMARK => 点击时取消自身已有的选中状态
mInitialTouchX -= animation.mX;
mInitialTouchY -= animation.mY;
//REMARK => 如果要执行新的元素动画，则需要先还原旧的元素状态
//有可能存在多个还原动画同时执行的情况，我们不等旧的还原动画执行完毕，直接取消旧的还原动画，然后执行新的还原动画
endRecoverAnimation(animation.mViewHolder, true);
if (mPendingCleanup.remove(animation.mViewHolder.itemView)) {
mCallback.clearView(mRecyclerView, animation.mViewHolder);
}
select(animation.mViewHolder, animation.mActionState);
updateDxDy(e, mSelectedFlags, 0);
}
}
} else if (action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_UP) {
if (mClick && action == MotionEvent.ACTION_UP) {
doChildClickEvent(e);
}
mActivePointerId = ACTIVE_POINTER_ID_NONE;
select(null, ACTION_STATE_IDLE);
} else if (mActivePointerId != ACTIVE_POINTER_ID_NONE) {
// in a non scroll orientation, if distance change is above threshold, we
// can select the item
final int index = e.findPointerIndex(mActivePointerId);
if (index >= 0) {
//REMARK => 判断是否已进入滑动状态
//如果已进入滑动状态，则记录新的mSelected，并禁用intercept功能，后面的事件将交由onTouchEvent方法处理
Console.debug("OnItemTouchListener.checkSelectForSwipe");
boolean ret = checkSelectForSwipe(action, e, index);
Console.debug("=>", "OnItemTouchListener.checkSelectForSwipe", ret);
}
} else if (action == MotionEvent.ACTION_MOVE) {
}
if (mVelocityTracker != null) {
mVelocityTracker.addMovement(e);
}
boolean ret = mSelected != null;
Console.debug("=>", "OnItemTouchListener.onInterceptTouchEvent", ret);
return ret;
}
@Override
public void onTouchEvent(RecyclerView recyclerView, MotionEvent e) {
Console.debug("OnItemTouchListener.onTouchEvent");
mGestureDetector.onTouchEvent(e);
if (mVelocityTracker != null) {
mVelocityTracker.addMovement(e);
}
if (mActivePointerId == ACTIVE_POINTER_ID_NONE) {
Console.debug("=>", "OnItemTouchListener.onTouchEvent", "void");
return;
}
final int action = e.getActionMasked();
final int activePointerIndex = e.findPointerIndex(mActivePointerId);
if (activePointerIndex >= 0) {
Console.debug("OnItemTouchListener.checkSelectForSwipe");
boolean ret = checkSelectForSwipe(action, e, activePointerIndex);
Console.debug("=>", "OnItemTouchListener.checkSelectForSwipe", ret);
}
ViewHolder viewHolder = mSelected;
if (viewHolder == null) {
Console.debug("=>", "OnItemTouchListener.onTouchEvent", "void");
return;
}
switch (action) {
case MotionEvent.ACTION_MOVE: {
// Find the index of the active pointer and fetch its position
if (activePointerIndex >= 0) {
float abs = Math.abs(initX - e.getX(0));
if (abs > 50) {
mClick = false;
}
//REMARK => 滑动和拖拽元素
updateDxDy(e, mSelectedFlags, activePointerIndex);
moveIfNecessary(viewHolder);
mRecyclerView.removeCallbacks(mScrollRunnable);
//REMARK => 拖拽到达边界时，继续滑动RecyclerView
mScrollRunnable.run();
mRecyclerView.invalidate();
}
break;
}
case MotionEvent.ACTION_CANCEL:
if (mVelocityTracker != null) {
mVelocityTracker.clear();
}
// fall through
case MotionEvent.ACTION_UP:
if (mClick) {
doChildClickEvent(e);
}
mClick = false;
select(null, ACTION_STATE_IDLE);
mActivePointerId = ACTIVE_POINTER_ID_NONE;
break;
case MotionEvent.ACTION_POINTER_UP: {
mClick = false;
final int pointerIndex = e.getActionIndex();
final int pointerId = e.getPointerId(pointerIndex);
if (pointerId == mActivePointerId) {
// This was our active pointer going up. Choose a new
// active pointer and adjust accordingly.
final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
mActivePointerId = e.getPointerId(newPointerIndex);
updateDxDy(e, mSelectedFlags, pointerIndex);
}
break;
}
default:
mClick = false;
}
Console.debug("=>", "OnItemTouchListener.onTouchEvent", "void");
}
@Override
public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
Console.debug("OnItemTouchListener.onRequestDisallowInterceptTouchEvent", "disallowIntercept", disallowIntercept);
if (!disallowIntercept) {
return;
}
select(null, ACTION_STATE_IDLE);
}
};
/**
* Temporary rect instance that is used when we need to lookup Item decorations.
*/
private Rect mTmpRect;
/**
* When user started to drag scroll. Reset when we don't scroll
*/
private long mDragScrollStartTimeInMs;
/**
* Creates an ItemTouchHelper that will work with the given Callback.
* <p>
* You can attach ItemTouchHelper to a RecyclerView via
* {@link #attachToRecyclerView(RecyclerView)}. Upon attaching, it will add an item decoration,
* an onItemTouchListener and a Child attach / detach listener to the RecyclerView.
*
* @param callback The Callback which controls the behavior of this touch helper.
*/
public ItemTouchHelper(Callback callback) {
mCallback = callback;
}
private static boolean hitTest(View child, float x, float y, float left, float top) {
return x >= left
&& x <= left + child.getWidth()
&& y >= top
&& y <= top + child.getHeight();
}
/**
* Attaches the ItemTouchHelper to the provided RecyclerView. If TouchHelper is already
* attached to a RecyclerView, it will first detach from the previous one. You can call this
* method with {@code null} to detach it from the current RecyclerView.
*
* @param recyclerView The RecyclerView instance to which you want to add this helper or
* {@code null} if you want to remove ItemTouchHelper from the current
* RecyclerView.
*/
public void attachToRecyclerView(@Nullable RecyclerView recyclerView) {
if (mRecyclerView == recyclerView) {
return; // nothing to do
}
if (mRecyclerView != null) {
destroyCallbacks();
}
mRecyclerView = recyclerView;
if (recyclerView != null) {
final Resources resources = recyclerView.getResources();
mSwipeEscapeVelocity = resources
.getDimension(R.dimen.item_touch_helper_swipe_escape_velocity);
mMaxSwipeVelocity = resources
.getDimension(R.dimen.item_touch_helper_swipe_escape_max_velocity);
setupCallbacks();
mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if (newState == RecyclerView.SCROLL_STATE_DRAGGING && mPreOpened != null) {
closeOpenedPreItem();
}
}
});
}
}
private void setupCallbacks() {
ViewConfiguration vc = ViewConfiguration.get(mRecyclerView.getContext());
mSlop = vc.getScaledTouchSlop();
mRecyclerView.addItemDecoration(this);
mRecyclerView.addOnItemTouchListener(mOnItemTouchListener);
mRecyclerView.addOnChildAttachStateChangeListener(this);
startGestureDetection();
}
private void destroyCallbacks() {
mRecyclerView.removeItemDecoration(this);
mRecyclerView.removeOnItemTouchListener(mOnItemTouchListener);
mRecyclerView.removeOnChildAttachStateChangeListener(this);
// clean all attached
final int recoverAnimSize = mRecoverAnimations.size();
for (int i = recoverAnimSize - 1; i >= 0; i--) {
final RecoverAnimation recoverAnimation = mRecoverAnimations.get(0);
mCallback.clearView(mRecyclerView, recoverAnimation.mViewHolder);
}
mRecoverAnimations.clear();
mOverdrawChild = null;
mOverdrawChildPosition = -1;
releaseVelocityTracker();
stopGestureDetection();
}
private void startGestureDetection() {
mItemTouchHelperGestureListener = new ItemTouchHelperGestureListener();
mGestureDetector = new GestureDetectorCompat(mRecyclerView.getContext(),
mItemTouchHelperGestureListener);
}
private void stopGestureDetection() {
if (mItemTouchHelperGestureListener != null) {
mItemTouchHelperGestureListener.doNotReactToLongPress();
mItemTouchHelperGestureListener = null;
}
if (mGestureDetector != null) {
mGestureDetector = null;
}
}
private void getSelectedDxDy(float[] outPosition) {
if ((mSelectedFlags & (LEFT | RIGHT)) != 0) {
outPosition[0] = mSelectedStartX + mDx - mSelected.itemView.getLeft();
} else {
outPosition[0] = mSelected.itemView.getTranslationX();
}
if ((mSelectedFlags & (UP | DOWN)) != 0) {
outPosition[1] = mSelectedStartY + mDy - mSelected.itemView.getTop();
} else {
outPosition[1] = mSelected.itemView.getTranslationY();
}
}
@Override
public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
float dx = 0, dy = 0;
if (mSelected != null) {
getSelectedDxDy(mTmpPosition);
dx = mTmpPosition[0];
dy = mTmpPosition[1];
}
mCallback.onDrawOver(c, parent, mSelected,
mRecoverAnimations, mActionState, dx, dy);
}
@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
// we don't know if RV changed something so we should invalidate this index.
mOverdrawChildPosition = -1;
float dx = 0, dy = 0;
if (mSelected != null) {
getSelectedDxDy(mTmpPosition);
dx = mTmpPosition[0];
dy = mTmpPosition[1];
}
mCallback.onDraw(c, parent, mSelected, mRecoverAnimations, mActionState, dx, dy);
}
protected String name(ViewHolder viewHolder) {
if (viewHolder == null)
return "ViewHolder@NULL";
return "ViewHolder@" + viewHolder.getAdapterPosition();
}
protected String name(int actionState) {
if (actionState == ACTION_STATE_IDLE)
return "ACTION_STATE_IDLE";
if (actionState == ACTION_STATE_SWIPE)
return "ACTION_STATE_SWIPE";
if (actionState == ACTION_STATE_DRAG)
return "ACTION_STATE_DRAG";
return "ACTION_STATE_UNKNWON";
}
/**
* Starts dragging or swiping the given View. Call with null if you want to clear it.
*
* @param selected The ViewHolder to drag or swipe. Can be null if you want to cancel the
* current action
* @param actionState The type of action
*/
//每次手按下开始Move的时候，和每次手松开Up的时候执行一次动画
//mSelected和mActionState为手势发生前的选中元素和活动状态
//selected和actionState为手势发生后的选中元素和活动状态
//手按下时，先判断有没有其它元素已选中，如果有，则先取消该元素的选中状态，通过动画还原至正常状态。再记录新的选中元素，以及该元素的操作类型是滑动还是拖拽
//手松开时，根据最后的手势位置，确定新的选中元素，是要取消动作，还是继续完成旧动作。这个是通过启动一个新的动画来自动完成的
//从以上逻辑，我们可以知道，控件运动，主要是通过三个渠道来实现的
//1. 滑动过程中，根据滑动位移，来动态调整控件位置，并进行重绘
//2. 手指按下后，旧的选中元素，通过动画自动还原至普通状态
//3. 手指松开后，新的选中元素，通过动画自动完成滑动、拖拽、取消等动作
void select(ViewHolder selected, int actionState) {
Console.debug("ItemTouchHelper.select", name(selected), name(actionState));
//REMARK => 如果目标元素和目标状态，都和当前一致，则什么都不做，继续执行旧动画
if (selected == mSelected && actionState == mActionState)
return;
mDragScrollStartTimeInMs = Long.MIN_VALUE;
final int prevActionState = mActionState;
mActionState = actionState;
if (actionState == ACTION_STATE_DRAG) {
// we remove after animation is complete. this means we only elevate the last drag
// child but that should perform good enough as it is very hard to start dragging a
// new child before the previous one settles.
mOverdrawChild = selected.itemView;
addChildDrawingOrderCallback();
}
int actionStateMask = (1 << (DIRECTION_FLAG_COUNT + DIRECTION_FLAG_COUNT * actionState)) - 1;
boolean preventLayout = false;
if (mSelected != null) {
final ViewHolder prevSelected = mSelected;
if (prevSelected.itemView.getParent() != null) {
final int swipeDir = prevActionState == ACTION_STATE_DRAG ? 0 : swipeIfNecessary(prevSelected);
releaseVelocityTracker();
// find where we should animate to
final float targetTranslateX, targetTranslateY;
int animationType;
switch (swipeDir) {
case LEFT:
case RIGHT:
case START:
case END:
targetTranslateY = 0;
targetTranslateX = Math.signum(mDx) * mRecyclerView.getWidth();
break;
case UP:
case DOWN:
targetTranslateX = 0;
targetTranslateY = Math.signum(mDy) * mRecyclerView.getHeight();
break;
default:
targetTranslateX = 0;
targetTranslateY = 0;
}
if (prevActionState == ACTION_STATE_DRAG) {
animationType = ANIMATION_TYPE_DRAG;
} else if (swipeDir > 0) {
animationType = ANIMATION_TYPE_SWIPE_SUCCESS;
} else {
animationType = ANIMATION_TYPE_SWIPE_CANCEL;
}
getSelectedDxDy(mTmpPosition);
final float currentTranslateX = mTmpPosition[0];
final float currentTranslateY = mTmpPosition[1];
//REMARK => 执行还原动画，将旧元素还原到普通状态
RecoverAnimation recoverAnimation = new RecoverAnimation(prevSelected, animationType, prevActionState, currentTranslateX, currentTranslateY, targetTranslateX, targetTranslateY) {
@Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
if (this.mOverridden) {
return;
}
if (swipeDir <= 0) {
// this is a drag or failed swipe. recover immediately
//REMARK => 清除上个选中元素的dx、dy、dz偏移动画
mCallback.clearView(mRecyclerView, prevSelected);
// full cleanup will happen on onDrawOver
} else {
// wait until remove animation is complete.
mPendingCleanup.add(prevSelected.itemView);
mPreOpened = prevSelected;
mIsPendingCleanup = true;
if (swipeDir > 0) {
// Animation might be ended by other animators during a layout.
// We defer callback to avoid editing adapter during a layout.
postDispatchSwipe(this, swipeDir);
}
}
// removed from the list after it is drawn for the last time
if (mOverdrawChild == prevSelected.itemView) {
removeChildDrawingOrderCallbackIfNecessary(prevSelected.itemView);
}
}
};
Console.debug("RecoverAnimation", currentTranslateX, currentTranslateY, targetTranslateX, targetTranslateY);
final long duration = mCallback.getAnimationDuration(mRecyclerView, animationType, targetTranslateX - currentTranslateX, targetTranslateY - currentTranslateY);
recoverAnimation.setDuration(duration);
mRecoverAnimations.add(recoverAnimation);
recoverAnimation.start();
preventLayout = true;
} else {
removeChildDrawingOrderCallbackIfNecessary(prevSelected.itemView);
mCallback.clearView(mRecyclerView, prevSelected);
}
mSelected = null;
}
if (selected != null) {
mSelectedFlags = (mCallback.getAbsoluteMovementFlags(mRecyclerView, selected) & actionStateMask) >> (mActionState * DIRECTION_FLAG_COUNT);
mSelectedStartX = selected.itemView.getLeft();
mSelectedStartY = selected.itemView.getTop();
mSelected = selected;
if (actionState == ACTION_STATE_DRAG) {
mSelected.itemView.performHapticFeedback(HapticFeedbackConstants.LONG_PRESS);
}
}
final ViewParent rvParent = mRecyclerView.getParent();
if (rvParent != null) {
rvParent.requestDisallowInterceptTouchEvent(mSelected != null);//REMARK => 禁止RecyclerView父控件拦截事件
}
if (!preventLayout) {
mRecyclerView.getLayoutManager().requestSimpleAnimationsInNextLayout();
}
mCallback.onSelectedChanged(mSelected, mActionState); //REMARK => 新元素被选中时，执行回调
mRecyclerView.invalidate();
}
void postDispatchSwipe(final RecoverAnimation anim, final int swipeDir) {
// wait until animations are complete.
mRecyclerView.post(new Runnable() {
@Override
public void run() {
if (mRecyclerView != null && mRecyclerView.isAttachedToWindow()
&& !anim.mOverridden
&& anim.mViewHolder.getAdapterPosition() != RecyclerView.NO_POSITION) {
final RecyclerView.ItemAnimator animator = mRecyclerView.getItemAnimator();
// if animator is running or we have other active recover animations, we try
// not to call onSwiped because DefaultItemAnimator is not good at merging
// animations. Instead, we wait and batch.
if ((animator == null || !animator.isRunning(null))
&& !hasRunningRecoverAnim()) {
mCallback.onSwiped(anim.mViewHolder, swipeDir);
} else {
mRecyclerView.post(this);
}
}
}
});
}
boolean hasRunningRecoverAnim() {
final int size = mRecoverAnimations.size();
for (int i = 0; i < size; i++) {
if (!mRecoverAnimations.get(i).mEnded) {
return true;
}
}
return false;
}
/**
* If user drags the view to the edge, trigger a scroll if necessary.
*/
boolean scrollIfNecessary() {
if (mSelected == null) {
mDragScrollStartTimeInMs = Long.MIN_VALUE;
return false;
}
final long now = System.currentTimeMillis();
final long scrollDuration = mDragScrollStartTimeInMs
== Long.MIN_VALUE ? 0 : now - mDragScrollStartTimeInMs;
RecyclerView.LayoutManager lm = mRecyclerView.getLayoutManager();
if (mTmpRect == null) {
mTmpRect = new Rect();
}
int scrollX = 0;
int scrollY = 0;
lm.calculateItemDecorationsForChild(mSelected.itemView, mTmpRect);
if (lm.canScrollHorizontally()) {
int curX = (int) (mSelectedStartX + mDx);
final int leftDiff = curX - mTmpRect.left - mRecyclerView.getPaddingLeft();
if (mDx < 0 && leftDiff < 0) {
scrollX = leftDiff;
} else if (mDx > 0) {
final int rightDiff =
curX + mSelected.itemView.getWidth() + mTmpRect.right
- (mRecyclerView.getWidth() - mRecyclerView.getPaddingRight());
if (rightDiff > 0) {
scrollX = rightDiff;
}
}
}
if (lm.canScrollVertically()) {
int curY = (int) (mSelectedStartY + mDy);
final int topDiff = curY - mTmpRect.top - mRecyclerView.getPaddingTop();
if (mDy < 0 && topDiff < 0) {
scrollY = topDiff;
} else if (mDy > 0) {
final int bottomDiff = curY + mSelected.itemView.getHeight() + mTmpRect.bottom
- (mRecyclerView.getHeight() - mRecyclerView.getPaddingBottom());
if (bottomDiff > 0) {
scrollY = bottomDiff;
}
}
}
if (scrollX != 0) {
scrollX = mCallback.interpolateOutOfBoundsScroll(mRecyclerView,
mSelected.itemView.getWidth(), scrollX,
mRecyclerView.getWidth(), scrollDuration);
}
if (scrollY != 0) {
scrollY = mCallback.interpolateOutOfBoundsScroll(mRecyclerView,
mSelected.itemView.getHeight(), scrollY,
mRecyclerView.getHeight(), scrollDuration);
}
if (scrollX != 0 || scrollY != 0) {
if (mDragScrollStartTimeInMs == Long.MIN_VALUE) {
mDragScrollStartTimeInMs = now;
}
mRecyclerView.scrollBy(scrollX, scrollY);
return true;
}
mDragScrollStartTimeInMs = Long.MIN_VALUE;
return false;
}
private List<ViewHolder> findSwapTargets(ViewHolder viewHolder) {
if (mSwapTargets == null) {
mSwapTargets = new ArrayList<ViewHolder>();
mDistances = new ArrayList<Integer>();
} else {
mSwapTargets.clear();
mDistances.clear();
}
final int margin = mCallback.getBoundingBoxMargin();
final int left = Math.round(mSelectedStartX + mDx) - margin;
final int top = Math.round(mSelectedStartY + mDy) - margin;
final int right = left + viewHolder.itemView.getWidth() + 2 * margin;
final int bottom = top + viewHolder.itemView.getHeight() + 2 * margin;
final int centerX = (left + right) / 2;
final int centerY = (top + bottom) / 2;
final RecyclerView.LayoutManager lm = mRecyclerView.getLayoutManager();
final int childCount = lm.getChildCount();
for (int i = 0; i < childCount; i++) {
View other = lm.getChildAt(i);
if (other == viewHolder.itemView) {
continue; //myself!
}
if (other.getBottom() < top || other.getTop() > bottom
|| other.getRight() < left || other.getLeft() > right) {
continue;
}
final ViewHolder otherVh = mRecyclerView.getChildViewHolder(other);
if (mCallback.canDropOver(mRecyclerView, mSelected, otherVh)) {
// find the index to add
final int dx = Math.abs(centerX - (other.getLeft() + other.getRight()) / 2);
final int dy = Math.abs(centerY - (other.getTop() + other.getBottom()) / 2);
final int dist = dx * dx + dy * dy;
int pos = 0;
final int cnt = mSwapTargets.size();
for (int j = 0; j < cnt; j++) {
if (dist > mDistances.get(j)) {
pos++;
} else {
break;
}
}
mSwapTargets.add(pos, otherVh);
mDistances.add(pos, dist);
}
}
return mSwapTargets;
}
/**
* Checks if we should swap w/ another view holder.
*/
//REMARK => 拖拽元素
void moveIfNecessary(ViewHolder viewHolder) {
if (mRecyclerView.isLayoutRequested())
return;
if (mActionState != ACTION_STATE_DRAG)
return;
final float threshold = mCallback.getMoveThreshold(viewHolder);
final int x = (int) (mSelectedStartX + mDx);
final int y = (int) (mSelectedStartY + mDy);
if (Math.abs(y - viewHolder.itemView.getTop()) < viewHolder.itemView.getHeight() * threshold && Math.abs(x - viewHolder.itemView.getLeft()) < viewHolder.itemView.getWidth() * threshold)
return;
List<ViewHolder> swapTargets = findSwapTargets(viewHolder);
if (swapTargets.size() == 0)
return;
// may swap.
ViewHolder target = mCallback.chooseDropTarget(viewHolder, swapTargets, x, y);
if (target == null) {
mSwapTargets.clear();
mDistances.clear();
return;
}
final int toPosition = target.getAdapterPosition();
final int fromPosition = viewHolder.getAdapterPosition();
//REMARK => 拖拽元素时，同时移动被交换的元素
// keep target visible
if (mCallback.onMove(mRecyclerView, viewHolder, target))
mCallback.onMoved(mRecyclerView, viewHolder, fromPosition, target, toPosition, x, y);
}
@Override
public void onChildViewAttachedToWindow(View view) {
}
@Override
public void onChildViewDetachedFromWindow(View view) {
removeChildDrawingOrderCallbackIfNecessary(view);
final ViewHolder holder = mRecyclerView.getChildViewHolder(view);
if (holder == null) {
return;
}
if (mSelected != null && holder == mSelected) {
select(null, ACTION_STATE_IDLE);
} else {
endRecoverAnimation(holder, false); // this may push it into pending cleanup list.
if (mPendingCleanup.remove(holder.itemView)) {
mCallback.clearView(mRecyclerView, holder);
}
}
}
/**
* Returns the animation type or 0 if cannot be found.
*/
int endRecoverAnimation(ViewHolder viewHolder, boolean override) {
final int recoverAnimSize = mRecoverAnimations.size();
for (int i = recoverAnimSize - 1; i >= 0; i--) {
final RecoverAnimation anim = mRecoverAnimations.get(i);
if (anim.mViewHolder == viewHolder) {
anim.mOverridden |= override;
if (!anim.mEnded) {
anim.cancel();
}
mRecoverAnimations.remove(i);
return anim.mAnimationType;
}
}
return 0;
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent,
RecyclerView.State state) {
outRect.setEmpty();
}
void obtainVelocityTracker() {
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
}
mVelocityTracker = VelocityTracker.obtain();
}
private void releaseVelocityTracker() {
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
}
private ViewHolder findSwipedView(MotionEvent motionEvent) {
final RecyclerView.LayoutManager lm = mRecyclerView.getLayoutManager();
if (mActivePointerId == ACTIVE_POINTER_ID_NONE) {
return null;
}
final int pointerIndex = motionEvent.findPointerIndex(mActivePointerId);
final float dx = motionEvent.getX(pointerIndex) - mInitialTouchX;
final float dy = motionEvent.getY(pointerIndex) - mInitialTouchY;
final float absDx = Math.abs(dx);
final float absDy = Math.abs(dy);
if (absDx < mSlop && absDy < mSlop) {
return null;
}
if (absDx > absDy && lm.canScrollHorizontally()) {
return null;
} else if (absDy > absDx && lm.canScrollVertically()) {
return null;
}
View child = findChildView(motionEvent);
if (child == null) {
return null;
}
return mRecyclerView.getChildViewHolder(child);
}
/**
* Checks whether we should select a View for swiping.
*/
boolean checkSelectForSwipe(int action, MotionEvent motionEvent, int pointerIndex) {
if (mSelected != null || action != MotionEvent.ACTION_MOVE
|| mActionState == ACTION_STATE_DRAG || !mCallback.isItemViewSwipeEnabled()) {
return false;
}
if (mRecyclerView.getScrollState() == RecyclerView.SCROLL_STATE_DRAGGING) {
return false;
}
final ViewHolder vh = findSwipedView(motionEvent);
if (vh == null) {
return false;
}
final int movementFlags = mCallback.getAbsoluteMovementFlags(mRecyclerView, vh);
final int swipeFlags = (movementFlags & ACTION_MODE_SWIPE_MASK)
>> (DIRECTION_FLAG_COUNT * ACTION_STATE_SWIPE);
if (swipeFlags == 0) {
return false;
}
// mDx and mDy are only set in allowed directions. We use custom x/y here instead of
// updateDxDy to avoid swiping if user moves more in the other direction
final float x = motionEvent.getX(pointerIndex);
final float y = motionEvent.getY(pointerIndex);
// Calculate the distance moved
final float dx = x - mInitialTouchX;
final float dy = y - mInitialTouchY;
// swipe target is chose w/o applying flags so it does not really check if swiping in that
// direction is allowed. This why here, we use mDx mDy to check slope value again.
final float absDx = Math.abs(dx);
final float absDy = Math.abs(dy);
if (absDx < mSlop && absDy < mSlop) {
return false;
}
if (absDx > absDy) {
if (dx < 0 && (swipeFlags & LEFT) == 0) {
return false;
}
if (dx > 0 && (swipeFlags & RIGHT) == 0) {
return false;
}
} else {
if (dy < 0 && (swipeFlags & UP) == 0) {
return false;
}
if (dy > 0 && (swipeFlags & DOWN) == 0) {
return false;
}
}
mDx = mDy = 0f;
mActivePointerId = motionEvent.getPointerId(0);
select(vh, ACTION_STATE_SWIPE);
if (mPreOpened != null && mPreOpened != vh) {
closeOpenedPreItem();
}
return true;
}
View findChildView(MotionEvent event) {
// first check elevated views, if none, then call RV
final float x = event.getX();
final float y = event.getY();
if (mSelected != null) {
final View selectedView = mSelected.itemView;
if (hitTest(selectedView, x, y, mSelectedStartX + mDx, mSelectedStartY + mDy)) {
return selectedView;
}
}
for (int i = mRecoverAnimations.size() - 1; i >= 0; i--) {
final RecoverAnimation anim = mRecoverAnimations.get(i);
final View view = anim.mViewHolder.itemView;
if (hitTest(view, x, y, anim.mX, anim.mY)) {
return view;
}
}
return mRecyclerView.findChildViewUnder(x, y);
}
/**
* Starts dragging the provided ViewHolder. By default, ItemTouchHelper starts a drag when a
* View is long pressed. You can disable that behavior by overriding
* {@link Callback#isLongPressDragEnabled()}.
* <p>
* For this method to work:
* <ul>
* <li>The provided ViewHolder must be a child of the RecyclerView to which this
* ItemTouchHelper
* is attached.</li>
* <li>{@link Callback} must have dragging enabled.</li>
* <li>There must be a previous touch event that was reported to the ItemTouchHelper
* through RecyclerView's ItemTouchListener mechanism. As long as no other ItemTouchListener
* grabs previous events, this should work as expected.</li>
* </ul>
* <p>
* For example, if you would like to let your user to be able to drag an Item by touching one
* of its descendants, you may implement it as follows:
* <pre>
* viewHolder.dragButton.setOnTouchListener(new View.OnTouchListener() {
* public boolean onTouch(View v, MotionEvent event) {
* if (MotionEvent.getActionMasked(event) == MotionEvent.ACTION_DOWN) {
* mItemTouchHelper.startDrag(viewHolder);
* }
* return false;
* }
* });
* </pre>
* <p>
*
* @param viewHolder The ViewHolder to start dragging. It must be a direct child of
* RecyclerView.
* @see Callback#isItemViewSwipeEnabled()
*/
public void startDrag(ViewHolder viewHolder) {
if (!mCallback.hasDragFlag(mRecyclerView, viewHolder)) {
return;
}
if (viewHolder.itemView.getParent() != mRecyclerView) {
return;
}
obtainVelocityTracker();
mDx = mDy = 0f;
select(viewHolder, ACTION_STATE_DRAG);
}
/**
* Starts swiping the provided ViewHolder. By default, ItemTouchHelper starts swiping a View
* when user swipes their finger (or mouse pointer) over the View. You can disable this
* behavior
* by overriding {@link Callback}
* <p>
* For this method to work:
* <ul>
* <li>The provided ViewHolder must be a child of the RecyclerView to which this
* ItemTouchHelper is attached.</li>
* <li>{@link Callback} must have swiping enabled.</li>
* <li>There must be a previous touch event that was reported to the ItemTouchHelper
* through RecyclerView's ItemTouchListener mechanism. As long as no other ItemTouchListener
* grabs previous events, this should work as expected.</li>
* </ul>
* <p>
* For example, if you would like to let your user to be able to swipe an Item by touching one
* of its descendants, you may implement it as follows:
* <pre>
* viewHolder.dragButton.setOnTouchListener(new View.OnTouchListener() {
* public boolean onTouch(View v, MotionEvent event) {
* if (MotionEvent.getActionMasked(event) == MotionEvent.ACTION_DOWN) {
* mItemTouchHelper.startSwipe(viewHolder);
* }
* return false;
* }
* });
* </pre>
*
* @param viewHolder The ViewHolder to start swiping. It must be a direct child of
* RecyclerView.
*/
public void startSwipe(ViewHolder viewHolder) {
if (!mCallback.hasSwipeFlag(mRecyclerView, viewHolder)) {
return;
}
if (viewHolder.itemView.getParent() != mRecyclerView) {
return;
}
obtainVelocityTracker();
mDx = mDy = 0f;
select(viewHolder, ACTION_STATE_SWIPE);
}
RecoverAnimation findAnimation(MotionEvent event) {
if (mRecoverAnimations.isEmpty()) {
return null;
}
View target = findChildView(event);
for (int i = mRecoverAnimations.size() - 1; i >= 0; i--) {
final RecoverAnimation anim = mRecoverAnimations.get(i);
if (anim.mViewHolder.itemView == target) {
return anim;
}
}
return null;
}
void updateDxDy(MotionEvent ev, int directionFlags, int pointerIndex) {
final float x = ev.getX(pointerIndex);
final float y = ev.getY(pointerIndex);
// Calculate the distance moved
mDx = x - mInitialTouchX;
mDy = y - mInitialTouchY;
if ((directionFlags & LEFT) == 0) {
mDx = Math.max(0, mDx);
}
if ((directionFlags & RIGHT) == 0) {
mDx = Math.min(0, mDx);
}
if ((directionFlags & UP) == 0) {
mDy = Math.max(0, mDy);
}
if ((directionFlags & DOWN) == 0) {
mDy = Math.min(0, mDy);
}
}
private int swipeIfNecessary(ViewHolder viewHolder) {
if (mActionState == ACTION_STATE_DRAG) {
return 0;
}
final int originalMovementFlags = mCallback.getMovementFlags(mRecyclerView, viewHolder);
final int absoluteMovementFlags = mCallback.convertToAbsoluteDirection(
originalMovementFlags,
ViewCompat.getLayoutDirection(mRecyclerView));
final int flags = (absoluteMovementFlags
& ACTION_MODE_SWIPE_MASK) >> (ACTION_STATE_SWIPE * DIRECTION_FLAG_COUNT);
if (flags == 0) {
return 0;
}
final int originalFlags = (originalMovementFlags
& ACTION_MODE_SWIPE_MASK) >> (ACTION_STATE_SWIPE * DIRECTION_FLAG_COUNT);
int swipeDir;
if (Math.abs(mDx) > Math.abs(mDy)) {
if ((swipeDir = checkHorizontalSwipe(viewHolder, flags)) > 0) {
// if swipe dir is not in original flags, it should be the relative direction
if ((originalFlags & swipeDir) == 0) {
// convert to relative
return Callback.convertToRelativeDirection(swipeDir,
ViewCompat.getLayoutDirection(mRecyclerView));
}
return swipeDir;
}
if ((swipeDir = checkVerticalSwipe(viewHolder, flags)) > 0) {
return swipeDir;
}
} else {
if ((swipeDir = checkVerticalSwipe(viewHolder, flags)) > 0) {
return swipeDir;
}
if ((swipeDir = checkHorizontalSwipe(viewHolder, flags)) > 0) {
// if swipe dir is not in original flags, it should be the relative direction
if ((originalFlags & swipeDir) == 0) {
// convert to relative
return Callback.convertToRelativeDirection(swipeDir,
ViewCompat.getLayoutDirection(mRecyclerView));
}
return swipeDir;
}
}
return 0;
}
private int checkHorizontalSwipe(ViewHolder viewHolder, int flags) {
if ((flags & (LEFT | RIGHT)) != 0) {
final int dirFlag = mDx > 0 ? RIGHT : LEFT;
if (mVelocityTracker != null && mActivePointerId > -1) {
mVelocityTracker.computeCurrentVelocity(PIXELS_PER_SECOND,
mCallback.getSwipeVelocityThreshold(mMaxSwipeVelocity));
final float xVelocity = mVelocityTracker.getXVelocity(mActivePointerId);
final float yVelocity = mVelocityTracker.getYVelocity(mActivePointerId);
final int velDirFlag = xVelocity > 0f ? RIGHT : LEFT;
final float absXVelocity = Math.abs(xVelocity);
if ((velDirFlag & flags) != 0 && dirFlag == velDirFlag
&& absXVelocity >= mCallback.getSwipeEscapeVelocity(mSwipeEscapeVelocity)
&& absXVelocity > Math.abs(yVelocity)) {
return velDirFlag;
}
}
final float threshold = mRecyclerView.getWidth() * mCallback
.getSwipeThreshold(viewHolder);
if ((flags & dirFlag) != 0 && Math.abs(mDx) > threshold) {
return dirFlag;
}
}
return 0;
}
private int checkVerticalSwipe(ViewHolder viewHolder, int flags) {
if ((flags & (UP | DOWN)) != 0) {
final int dirFlag = mDy > 0 ? DOWN : UP;
if (mVelocityTracker != null && mActivePointerId > -1) {
mVelocityTracker.computeCurrentVelocity(PIXELS_PER_SECOND,
mCallback.getSwipeVelocityThreshold(mMaxSwipeVelocity));
final float xVelocity = mVelocityTracker.getXVelocity(mActivePointerId);
final float yVelocity = mVelocityTracker.getYVelocity(mActivePointerId);
final int velDirFlag = yVelocity > 0f ? DOWN : UP;
final float absYVelocity = Math.abs(yVelocity);
if ((velDirFlag & flags) != 0 && velDirFlag == dirFlag
&& absYVelocity >= mCallback.getSwipeEscapeVelocity(mSwipeEscapeVelocity)
&& absYVelocity > Math.abs(xVelocity)) {
return velDirFlag;
}
}
final float threshold = mRecyclerView.getHeight() * mCallback
.getSwipeThreshold(viewHolder);
if ((flags & dirFlag) != 0 && Math.abs(mDy) > threshold) {
return dirFlag;
}
}
return 0;
}
private void addChildDrawingOrderCallback() {
if (Build.VERSION.SDK_INT >= 21) {
return; // we use elevation on Lollipop
}
if (mChildDrawingOrderCallback == null) {
mChildDrawingOrderCallback = new RecyclerView.ChildDrawingOrderCallback() {
@Override
public int onGetChildDrawingOrder(int childCount, int i) {
if (mOverdrawChild == null) {
return i;
}
int childPosition = mOverdrawChildPosition;
if (childPosition == -1) {
childPosition = mRecyclerView.indexOfChild(mOverdrawChild);
mOverdrawChildPosition = childPosition;
}
if (i == childCount - 1) {
return childPosition;
}
return i < childPosition ? i : i + 1;
}
};
}
mRecyclerView.setChildDrawingOrderCallback(mChildDrawingOrderCallback);
}
void removeChildDrawingOrderCallbackIfNecessary(View view) {
if (view == mOverdrawChild) {
mOverdrawChild = null;
// only remove if we've added
if (mChildDrawingOrderCallback != null) {
mRecyclerView.setChildDrawingOrderCallback(null);
}
}
}
/**
* An interface which can be implemented by LayoutManager for better integration with
* {@link ItemTouchHelper}.
*/
public interface ViewDropHandler {
/**
* Called by the {@link ItemTouchHelper} after a View is dropped over another View.
* <p>
* A LayoutManager should implement this interface to get ready for the upcoming move
* operation.
* <p>
* For example, LinearLayoutManager sets up a "scrollToPositionWithOffset" calls so that
* the View under drag will be used as an anchor View while calculating the next layout,
* making layout stay consistent.
*
* @param view The View which is being dragged. It is very likely that user is still
* dragging this View so there might be other
* {@link #prepareForDrop(View, View, int, int)} after this one.
* @param target The target view which is being dropped on.
* @param x The <code>left</code> offset of the View that is being dragged. This value
* includes the movement caused by the user.
* @param y The <code>top</code> offset of the View that is being dragged. This value
* includes the movement caused by the user.
*/
void prepareForDrop(View view, View target, int x, int y);
}
/**
* This class is the contract between ItemTouchHelper and your application. It lets you control
* which touch behaviors are enabled per each ViewHolder and also receive callbacks when user
* performs these actions.
* <p>
* To control which actions user can take on each view, you should override
* {@link #getMovementFlags(RecyclerView, ViewHolder)} and return appropriate set
* of direction flags. ({@link #LEFT}, {@link #RIGHT}, {@link #START}, {@link #END},
* {@link #UP}, {@link #DOWN}). You can use
* {@link #makeMovementFlags(int, int)} to easily construct it. Alternatively, you can use
* {@link SimpleCallback}.
* <p>
* If user drags an item, ItemTouchHelper will call
* {@link Callback#onMove(RecyclerView, ViewHolder, ViewHolder)
* onMove(recyclerView, dragged, target)}.
* Upon receiving this callback, you should move the item from the old position
* ({@code dragged.getAdapterPosition()}) to new position ({@code target.getAdapterPosition()})
* in your adapter and also call {@link RecyclerView.Adapter#notifyItemMoved(int, int)}.
* To control where a View can be dropped, you can override
* {@link #canDropOver(RecyclerView, ViewHolder, ViewHolder)}. When a
* dragging View overlaps multiple other views, Callback chooses the closest View with which
* dragged View might have changed positions. Although this approach works for many use cases,
* if you have a custom LayoutManager, you can override
* {@link #chooseDropTarget(ViewHolder, List, int, int)} to select a
* custom drop target.
* <p>
* When a View is swiped, ItemTouchHelper animates it until it goes out of bounds, then calls
* {@link #onSwiped(ViewHolder, int)}. At this point, you should update your
* adapter (e.g. remove the item) and call related Adapter#notify event.
*/
@SuppressWarnings("UnusedParameters")
public abstract static class Callback {
public static final int DEFAULT_DRAG_ANIMATION_DURATION = 200;
public static final int DEFAULT_SWIPE_ANIMATION_DURATION = 250;
static final int RELATIVE_DIR_FLAGS = START | END
| ((START | END) << DIRECTION_FLAG_COUNT)
| ((START | END) << (2 * DIRECTION_FLAG_COUNT));
private static final ItemTouchUIUtil sUICallback;
private static final int ABS_HORIZONTAL_DIR_FLAGS = LEFT | RIGHT
| ((LEFT | RIGHT) << DIRECTION_FLAG_COUNT)
| ((LEFT | RIGHT) << (2 * DIRECTION_FLAG_COUNT));
private static final Interpolator sDragScrollInterpolator = new Interpolator() {
@Override
public float getInterpolation(float t) {
return t * t * t * t * t;
}
};
private static final Interpolator sDragViewScrollCapInterpolator = new Interpolator() {
@Override
public float getInterpolation(float t) {
t -= 1.0f;
return t * t * t * t * t + 1.0f;
}
};
/**
* Drag scroll speed keeps accelerating until this many milliseconds before being capped.
*/
private static final long DRAG_SCROLL_ACCELERATION_LIMIT_TIME_MS = 2000;
private int mCachedMaxScrollSpeed = -1;
static {
sUICallback = new ItemTouchUIUtilImpl();
}
/**
* Returns the {@link ItemTouchUIUtil} that is used by the {@link Callback} class for
* visual
* changes on Views in response to user interactions. {@link ItemTouchUIUtil} has different
* implementations for different platform versions.
* <p>
* By default, {@link Callback} applies these changes on
* {@link ViewHolder#itemView}.
* <p>
* For example, if you have a use case where you only want the text to move when user
* swipes over the view, you can do the following:
* <pre>
* public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder){
* getDefaultUIUtil().clearView(((ItemTouchViewHolder) viewHolder).textView);
* }
* public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
* if (viewHolder != null){
* getDefaultUIUtil().onSelected(((ItemTouchViewHolder) viewHolder).textView);
* }
* }
* public void onChildDraw(Canvas c, RecyclerView recyclerView,
* RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState,
* boolean isCurrentlyActive) {
* getDefaultUIUtil().onDraw(c, recyclerView,
* ((ItemTouchViewHolder) viewHolder).textView, dX, dY,
* actionState, isCurrentlyActive);
* return true;
* }
* public void onChildDrawOver(Canvas c, RecyclerView recyclerView,
* RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState,
* boolean isCurrentlyActive) {
* getDefaultUIUtil().onDrawOver(c, recyclerView,
* ((ItemTouchViewHolder) viewHolder).textView, dX, dY,
* actionState, isCurrentlyActive);
* return true;
* }
* </pre>
*
* @return The {@link ItemTouchUIUtil} instance that is used by the {@link Callback}
*/
public static ItemTouchUIUtil getDefaultUIUtil() {
return sUICallback;
}
/**
* Replaces a movement direction with its relative version by taking layout direction into
* account.
*
* @param flags The flag value that include any number of movement flags.
* @param layoutDirection The layout direction of the View. Can be obtained from
* {@link ViewCompat#getLayoutDirection(View)}.
* @return Updated flags which uses relative flags ({@link #START}, {@link #END}) instead
* of {@link #LEFT}, {@link #RIGHT}.
* @see #convertToAbsoluteDirection(int, int)
*/
public static int convertToRelativeDirection(int flags, int layoutDirection) {
int masked = flags & ABS_HORIZONTAL_DIR_FLAGS;
if (masked == 0) {
return flags; // does not have any abs flags, good.
}
flags &= ~masked; //remove left / right.
if (layoutDirection == ViewCompat.LAYOUT_DIRECTION_LTR) {
// no change. just OR with 2 bits shifted mask and return
flags |= masked << 2; // START is 2 bits after LEFT, END is 2 bits after RIGHT.
return flags;
} else {
// add RIGHT flag as START
flags |= ((masked << 1) & ~ABS_HORIZONTAL_DIR_FLAGS);
// first clean RIGHT bit then add LEFT flag as END
flags |= ((masked << 1) & ABS_HORIZONTAL_DIR_FLAGS) << 2;
}
return flags;
}
/**
* Convenience method to create movement flags.
* <p>
* For instance, if you want to let your items be drag & dropped vertically and swiped
* left to be dismissed, you can call this method with:
* <code>makeMovementFlags(UP | DOWN, LEFT);</code>
*
* @param dragFlags The directions in which the item can be dragged.
* @param swipeFlags The directions in which the item can be swiped.
* @return Returns an integer composed of the given drag and swipe flags.
*/
public static int makeMovementFlags(int dragFlags, int swipeFlags) {
return makeFlag(ACTION_STATE_IDLE, swipeFlags | dragFlags)
| makeFlag(ACTION_STATE_SWIPE, swipeFlags)
| makeFlag(ACTION_STATE_DRAG, dragFlags);
}
/**
* Shifts the given direction flags to the offset of the given action state.
*
* @param actionState The action state you want to get flags in. Should be one of
* {@link #ACTION_STATE_IDLE}, {@link #ACTION_STATE_SWIPE} or
* {@link #ACTION_STATE_DRAG}.
* @param directions The direction flags. Can be composed from {@link #UP}, {@link #DOWN},
* {@link #RIGHT}, {@link #LEFT} {@link #START} and {@link #END}.
* @return And integer that represents the given directions in the provided actionState.
*/
public static int makeFlag(int actionState, int directions) {
return directions << (actionState * DIRECTION_FLAG_COUNT);
}
/**
* Should return a composite flag which defines the enabled move directions in each state
* (idle, swiping, dragging).
* <p>
* Instead of composing this flag manually, you can use {@link #makeMovementFlags(int,
* int)}
* or {@link #makeFlag(int, int)}.
* <p>
* This flag is composed of 3 sets of 8 bits, where first 8 bits are for IDLE state, next
* 8 bits are for SWIPE state and third 8 bits are for DRAG state.
* Each 8 bit sections can be constructed by simply OR'ing direction flags defined in
* {@link ItemTouchHelper}.
* <p>
* For example, if you want it to allow swiping LEFT and RIGHT but only allow starting to
* swipe by swiping RIGHT, you can return:
* <pre>
* makeFlag(ACTION_STATE_IDLE, RIGHT) | makeFlag(ACTION_STATE_SWIPE, LEFT | RIGHT);
* </pre>
* This means, allow right movement while IDLE and allow right and left movement while
* swiping.
*
* @param recyclerView The RecyclerView to which ItemTouchHelper is attached.
* @param viewHolder The ViewHolder for which the movement information is necessary.
* @return flags specifying which movements are allowed on this ViewHolder.
* @see #makeMovementFlags(int, int)
* @see #makeFlag(int, int)
*/
public abstract int getMovementFlags(RecyclerView recyclerView,
ViewHolder viewHolder);
/**
* Converts a given set of flags to absolution direction which means {@link #START} and
* {@link #END} are replaced with {@link #LEFT} and {@link #RIGHT} depending on the layout
* direction.
*
* @param flags The flag value that include any number of movement flags.
* @param layoutDirection The layout direction of the RecyclerView.
* @return Updated flags which includes only absolute direction values.
*/
public int convertToAbsoluteDirection(int flags, int layoutDirection) {
int masked = flags & RELATIVE_DIR_FLAGS;
if (masked == 0) {
return flags; // does not have any relative flags, good.
}
flags &= ~masked; //remove start / end
if (layoutDirection == ViewCompat.LAYOUT_DIRECTION_LTR) {
// no change. just OR with 2 bits shifted mask and return
flags |= masked >> 2; // START is 2 bits after LEFT, END is 2 bits after RIGHT.
return flags;
} else {
// add START flag as RIGHT
flags |= ((masked >> 1) & ~RELATIVE_DIR_FLAGS);
// first clean start bit then add END flag as LEFT
flags |= ((masked >> 1) & RELATIVE_DIR_FLAGS) >> 2;
}
return flags;
}
final int getAbsoluteMovementFlags(RecyclerView recyclerView,
ViewHolder viewHolder) {
final int flags = getMovementFlags(recyclerView, viewHolder);
return convertToAbsoluteDirection(flags, ViewCompat.getLayoutDirection(recyclerView));
}
boolean hasDragFlag(RecyclerView recyclerView, ViewHolder viewHolder) {
final int flags = getAbsoluteMovementFlags(recyclerView, viewHolder);
return (flags & ACTION_MODE_DRAG_MASK) != 0;
}
boolean hasSwipeFlag(RecyclerView recyclerView,
ViewHolder viewHolder) {
final int flags = getAbsoluteMovementFlags(recyclerView, viewHolder);
return (flags & ACTION_MODE_SWIPE_MASK) != 0;
}
/**
* Return true if the current ViewHolder can be dropped over the the target ViewHolder.
* <p>
* This method is used when selecting drop target for the dragged View. After Views are
* eliminated either via bounds check or via this method, resulting set of views will be
* passed to {@link #chooseDropTarget(ViewHolder, List, int, int)}.
* <p>
* Default implementation returns true.
*
* @param recyclerView The RecyclerView to which ItemTouchHelper is attached to.
* @param current The ViewHolder that user is dragging.
* @param target The ViewHolder which is below the dragged ViewHolder.
* @return True if the dragged ViewHolder can be replaced with the target ViewHolder, false
* otherwise.
*/
public boolean canDropOver(RecyclerView recyclerView, ViewHolder current,
ViewHolder target) {
return true;
}
/**
* Called when ItemTouchHelper wants to move the dragged item from its old position to
* the new position.
* <p>
* If this method returns true, ItemTouchHelper assumes {@code viewHolder} has been moved
* to the adapter position of {@code target} ViewHolder
* ({@link ViewHolder#getAdapterPosition()
* ViewHolder#getAdapterPosition()}).
* <p>
* If you don't support drag & drop, this method will never be called.
*
* @param recyclerView The RecyclerView to which ItemTouchHelper is attached to.
* @param viewHolder The ViewHolder which is being dragged by the user.
* @param target The ViewHolder over which the currently active item is being
* dragged.
* @return True if the {@code viewHolder} has been moved to the adapter position of
* {@code target}.
* @see #onMoved(RecyclerView, ViewHolder, int, ViewHolder, int, int, int)
*/
public abstract boolean onMove(RecyclerView recyclerView,
ViewHolder viewHolder, ViewHolder target);
/**
* Returns whether ItemTouchHelper should start a drag and drop operation if an item is
* long pressed.
* <p>
* Default value returns true but you may want to disable this if you want to start
* dragging on a custom view touch using {@link #startDrag(ViewHolder)}.
*
* @return True if ItemTouchHelper should start dragging an item when it is long pressed,
* false otherwise. Default value is <code>true</code>.
* @see #startDrag(ViewHolder)
*/
public boolean isLongPressDragEnabled() {
return true;
}
/**
* Returns whether ItemTouchHelper should start a swipe operation if a pointer is swiped
* over the View.
* <p>
* Default value returns true but you may want to disable this if you want to start
* swiping on a custom view touch using {@link #startSwipe(ViewHolder)}.
*
* @return True if ItemTouchHelper should start swiping an item when user swipes a pointer
* over the View, false otherwise. Default value is <code>true</code>.
* @see #startSwipe(ViewHolder)
*/
public boolean isItemViewSwipeEnabled() {
return true;
}
/**
* When finding views under a dragged view, by default, ItemTouchHelper searches for views
* that overlap with the dragged View. By overriding this method, you can extend or shrink
* the search box.
*
* @return The extra margin to be added to the hit box of the dragged View.
*/
public int getBoundingBoxMargin() {
return 0;
}
/**
* Returns the fraction that the user should move the View to be considered as swiped.
* The fraction is calculated with respect to RecyclerView's bounds.
* <p>
* Default value is .5f, which means, to swipe a View, user must move the View at least
* half of RecyclerView's width or height, depending on the swipe direction.
*
* @param viewHolder The ViewHolder that is being dragged.
* @return A float value that denotes the fraction of the View size. Default value
* is .5f .
*/
public float getSwipeThreshold(ViewHolder viewHolder) {
return .5f;
}
/**
* Returns the fraction that the user should move the View to be considered as it is
* dragged. After a view is moved this amount, ItemTouchHelper starts checking for Views
* below it for a possible drop.
*
* @param viewHolder The ViewHolder that is being dragged.
* @return A float value that denotes the fraction of the View size. Default value is
* .5f .
*/
public float getMoveThreshold(ViewHolder viewHolder) {
return .5f;
}
/**
* Defines the minimum velocity which will be considered as a swipe action by the user.
* <p>
* You can increase this value to make it harder to swipe or decrease it to make it easier.
* Keep in mind that ItemTouchHelper also checks the perpendicular velocity and makes sure
* current direction velocity is larger then the perpendicular one. Otherwise, user's
* movement is ambiguous. You can change the threshold by overriding
* {@link #getSwipeVelocityThreshold(float)}.
* <p>
* The velocity is calculated in pixels per second.
* <p>
* The default framework value is passed as a parameter so that you can modify it with a
* multiplier.
*
* @param defaultValue The default value (in pixels per second) used by the
* ItemTouchHelper.
* @return The minimum swipe velocity. The default implementation returns the
* <code>defaultValue</code> parameter.
* @see #getSwipeVelocityThreshold(float)
* @see #getSwipeThreshold(ViewHolder)
*/
public float getSwipeEscapeVelocity(float defaultValue) {
return defaultValue;
}
/**
* Defines the maximum velocity ItemTouchHelper will ever calculate for pointer movements.
* <p>
* To consider a movement as swipe, ItemTouchHelper requires it to be larger than the
* perpendicular movement. If both directions reach to the max threshold, none of them will
* be considered as a swipe because it is usually an indication that user rather tried to
* scroll then swipe.
* <p>
* The velocity is calculated in pixels per second.
* <p>
* You can customize this behavior by changing this method. If you increase the value, it
* will be easier for the user to swipe diagonally and if you decrease the value, user will
* need to make a rather straight finger movement to trigger a swipe.
*
* @param defaultValue The default value(in pixels per second) used by the ItemTouchHelper.
* @return The velocity cap for pointer movements. The default implementation returns the
* <code>defaultValue</code> parameter.
* @see #getSwipeEscapeVelocity(float)
*/
public float getSwipeVelocityThreshold(float defaultValue) {
return defaultValue;
}
/**
* Called by ItemTouchHelper to select a drop target from the list of ViewHolders that
* are under the dragged View.
* <p>
* Default implementation filters the View with which dragged item have changed position
* in the drag direction. For instance, if the view is dragged UP, it compares the
* <code>view.getTop()</code> of the two views before and after drag started. If that value
* is different, the target view passes the filter.
* <p>
* Among these Views which pass the test, the one closest to the dragged view is chosen.
* <p>
* This method is called on the main thread every time user moves the View. If you want to
* override it, make sure it does not do any expensive operations.
*
* @param selected The ViewHolder being dragged by the user.
* @param dropTargets The list of ViewHolder that are under the dragged View and
* candidate as a drop.
* @param curX The updated left value of the dragged View after drag translations
* are applied. This value does not include margins added by
* {@link RecyclerView.ItemDecoration}s.
* @param curY The updated top value of the dragged View after drag translations
* are applied. This value does not include margins added by
* {@link RecyclerView.ItemDecoration}s.
* @return A ViewHolder to whose position the dragged ViewHolder should be
* moved to.
*/
public ViewHolder chooseDropTarget(ViewHolder selected,
List<ViewHolder> dropTargets, int curX, int curY) {
int right = curX + selected.itemView.getWidth();
int bottom = curY + selected.itemView.getHeight();
ViewHolder winner = null;
int winnerScore = -1;
final int dx = curX - selected.itemView.getLeft();
final int dy = curY - selected.itemView.getTop();
final int targetsSize = dropTargets.size();
for (int i = 0; i < targetsSize; i++) {
final ViewHolder target = dropTargets.get(i);
if (dx > 0) {
int diff = target.itemView.getRight() - right;
if (diff < 0 && target.itemView.getRight() > selected.itemView.getRight()) {
final int score = Math.abs(diff);
if (score > winnerScore) {
winnerScore = score;
winner = target;
}
}
}
if (dx < 0) {
int diff = target.itemView.getLeft() - curX;
if (diff > 0 && target.itemView.getLeft() < selected.itemView.getLeft()) {
final int score = Math.abs(diff);
if (score > winnerScore) {
winnerScore = score;
winner = target;
}
}
}
if (dy < 0) {
int diff = target.itemView.getTop() - curY;
if (diff > 0 && target.itemView.getTop() < selected.itemView.getTop()) {
final int score = Math.abs(diff);
if (score > winnerScore) {
winnerScore = score;
winner = target;
}
}
}
if (dy > 0) {
int diff = target.itemView.getBottom() - bottom;
if (diff < 0 && target.itemView.getBottom() > selected.itemView.getBottom()) {
final int score = Math.abs(diff);
if (score > winnerScore) {
winnerScore = score;
winner = target;
}
}
}
}
return winner;
}
/**
* Called when a ViewHolder is swiped by the user.
* <p>
* If you are returning relative directions ({@link #START} , {@link #END}) from the
* {@link #getMovementFlags(RecyclerView, ViewHolder)} method, this method
* will also use relative directions. Otherwise, it will use absolute directions.
* <p>
* If you don't support swiping, this method will never be called.
* <p>
* ItemTouchHelper will keep a reference to the View until it is detached from
* RecyclerView.
* As soon as it is detached, ItemTouchHelper will call
* {@link #clearView(RecyclerView, ViewHolder)}.
*
* @param viewHolder The ViewHolder which has been swiped by the user.
* @param direction The direction to which the ViewHolder is swiped. It is one of
* {@link #UP}, {@link #DOWN},
* {@link #LEFT} or {@link #RIGHT}. If your
* {@link #getMovementFlags(RecyclerView, ViewHolder)}
* method
* returned relative flags instead of {@link #LEFT} / {@link #RIGHT};
* `direction` will be relative as well. ({@link #START} or {@link
* #END}).
*/
public abstract void onSwiped(ViewHolder viewHolder, int direction);
/**
* Called when the ViewHolder swiped or dragged by the ItemTouchHelper is changed.
* <p/>
* If you override this method, you should call super.
*
* @param viewHolder The new ViewHolder that is being swiped or dragged. Might be null if
* it is cleared.
* @param actionState One of {@link ItemTouchHelper#ACTION_STATE_IDLE},
* {@link ItemTouchHelper#ACTION_STATE_SWIPE} or
* {@link ItemTouchHelper#ACTION_STATE_DRAG}.
* @see #clearView(RecyclerView, ViewHolder)
*/
public void onSelectedChanged(ViewHolder viewHolder, int actionState) {
if (viewHolder != null) {
sUICallback.onSelected(viewHolder.itemView);
}
}
private int getMaxDragScroll(RecyclerView recyclerView) {
if (mCachedMaxScrollSpeed == -1) {
mCachedMaxScrollSpeed = recyclerView.getResources().getDimensionPixelSize(
R.dimen.item_touch_helper_max_drag_scroll_per_frame);
}
return mCachedMaxScrollSpeed;
}
/**
* Called when {@link #onMove(RecyclerView, ViewHolder, ViewHolder)} returns true.
* <p>
* ItemTouchHelper does not create an extra Bitmap or View while dragging, instead, it
* modifies the existing View. Because of this reason, it is important that the View is
* still part of the layout after it is moved. This may not work as intended when swapped
* Views are close to RecyclerView bounds or there are gaps between them (e.g. other Views
* which were not eligible for dropping over).
* <p>
* This method is responsible to give necessary hint to the LayoutManager so that it will
* keep the View in visible area. For example, for LinearLayoutManager, this is as simple
* as calling {@link LinearLayoutManager#scrollToPositionWithOffset(int, int)}.
* <p>
* Default implementation calls {@link RecyclerView#scrollToPosition(int)} if the View's
* new position is likely to be out of bounds.
* <p>
* It is important to ensure the ViewHolder will stay visible as otherwise, it might be
* removed by the LayoutManager if the move causes the View to go out of bounds. In that
* case, drag will end prematurely.
*
* @param recyclerView The RecyclerView controlled by the ItemTouchHelper.
* @param viewHolder The ViewHolder under user's control.
* @param fromPos The previous adapter position of the dragged item (before it was
* moved).
* @param target The ViewHolder on which the currently active item has been dropped.
* @param toPos The new adapter position of the dragged item.
* @param x The updated left value of the dragged View after drag translations
* are applied. This value does not include margins added by
* {@link RecyclerView.ItemDecoration}s.
* @param y The updated top value of the dragged View after drag translations
* are applied. This value does not include margins added by
* {@link RecyclerView.ItemDecoration}s.
*/
public void onMoved(final RecyclerView recyclerView,
final ViewHolder viewHolder, int fromPos, final ViewHolder target, int toPos, int x,
int y) {
final RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
if (layoutManager instanceof ViewDropHandler) {
((ViewDropHandler) layoutManager).prepareForDrop(viewHolder.itemView,
target.itemView, x, y);
return;
}
// if layout manager cannot handle it, do some guesswork
if (layoutManager.canScrollHorizontally()) {
final int minLeft = layoutManager.getDecoratedLeft(target.itemView);
if (minLeft <= recyclerView.getPaddingLeft()) {
recyclerView.scrollToPosition(toPos);
}
final int maxRight = layoutManager.getDecoratedRight(target.itemView);
if (maxRight >= recyclerView.getWidth() - recyclerView.getPaddingRight()) {
recyclerView.scrollToPosition(toPos);
}
}
if (layoutManager.canScrollVertically()) {
final int minTop = layoutManager.getDecoratedTop(target.itemView);
if (minTop <= recyclerView.getPaddingTop()) {
recyclerView.scrollToPosition(toPos);
}
final int maxBottom = layoutManager.getDecoratedBottom(target.itemView);
if (maxBottom >= recyclerView.getHeight() - recyclerView.getPaddingBottom()) {
recyclerView.scrollToPosition(toPos);
}
}
}
void onDraw(Canvas c, RecyclerView parent, ViewHolder selected,
List<RecoverAnimation> recoverAnimationList,
int actionState, float dX, float dY) {
final int recoverAnimSize = recoverAnimationList.size();
for (int i = 0; i < recoverAnimSize; i++) {
final RecoverAnimation anim = recoverAnimationList.get(i);
anim.update();
final int count = c.save();
onChildDraw(c, parent, anim.mViewHolder, anim.mX, anim.mY, anim.mActionState, false);
c.restoreToCount(count);
}
if (selected != null) {
final int count = c.save();
onChildDraw(c, parent, selected, dX, dY, actionState, true);
c.restoreToCount(count);
}
}
void onDrawOver(Canvas c, RecyclerView parent, ViewHolder selected,
List<RecoverAnimation> recoverAnimationList,
int actionState, float dX, float dY) {
final int recoverAnimSize = recoverAnimationList.size();
for (int i = 0; i < recoverAnimSize; i++) {
final RecoverAnimation anim = recoverAnimationList.get(i);
final int count = c.save();
onChildDrawOver(c, parent, anim.mViewHolder, anim.mX, anim.mY, anim.mActionState,
false);
c.restoreToCount(count);
}
if (selected != null) {
final int count = c.save();
onChildDrawOver(c, parent, selected, dX, dY, actionState, true);
c.restoreToCount(count);
}
boolean hasRunningAnimation = false;
for (int i = recoverAnimSize - 1; i >= 0; i--) {
final RecoverAnimation anim = recoverAnimationList.get(i);
if (anim.mEnded && !anim.mIsPendingCleanup) {
recoverAnimationList.remove(i);
} else if (!anim.mEnded) {
hasRunningAnimation = true;
}
}
if (hasRunningAnimation) {
parent.invalidate();
}
}
/**
* Called by the ItemTouchHelper when the user interaction with an element is over and it
* also completed its animation.
* <p>
* This is a good place to clear all changes on the View that was done in
* {@link #onSelectedChanged(ViewHolder, int)},
* {@link #onChildDraw(Canvas, RecyclerView, ViewHolder, float, float, int,
* boolean)} or
* {@link #onChildDrawOver(Canvas, RecyclerView, ViewHolder, float, float, int, boolean)}.
*
* @param recyclerView The RecyclerView which is controlled by the ItemTouchHelper.
* @param viewHolder The View that was interacted by the user.
*/
//清除上个选中元素的dx、dy、dz偏移动画
public void clearView(RecyclerView recyclerView, ViewHolder viewHolder) {
sUICallback.clearView(viewHolder.itemView);
}
/**
* Called by ItemTouchHelper on RecyclerView's onDraw callback.
* <p>
* If you would like to customize how your View's respond to user interactions, this is
* a good place to override.
* <p>
* Default implementation translates the child by the given <code>dX</code>,
* <code>dY</code>.
* ItemTouchHelper also takes care of drawing the child after other children if it is being
* dragged. This is done using child re-ordering mechanism. On platforms prior to L, this
* is
* achieved via {@link ViewGroup#getChildDrawingOrder(int, int)} and on L
* and after, it changes View's elevation value to be greater than all other children.)
*
* @param c The canvas which RecyclerView is drawing its children
* @param recyclerView The RecyclerView to which ItemTouchHelper is attached to
* @param viewHolder The ViewHolder which is being interacted by the User or it was
* interacted and simply animating to its original position
* @param dX The amount of horizontal displacement caused by user's action
* @param dY The amount of vertical displacement caused by user's action
* @param actionState The type of interaction on the View. Is either {@link
* #ACTION_STATE_DRAG} or {@link #ACTION_STATE_SWIPE}.
* @param isCurrentlyActive True if this view is currently being controlled by the user or
* false it is simply animating back to its original state.
* @see #onChildDrawOver(Canvas, RecyclerView, ViewHolder, float, float, int,
* boolean)
*/
public void onChildDraw(Canvas c, RecyclerView recyclerView, ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
sUICallback.onDraw(c, recyclerView, viewHolder.itemView, dX, dY, actionState, isCurrentlyActive);
}
/**
* Called by ItemTouchHelper on RecyclerView's onDraw callback.
* <p>
* If you would like to customize how your View's respond to user interactions, this is
* a good place to override.
* <p>
* Default implementation translates the child by the given <code>dX</code>,
* <code>dY</code>.
* ItemTouchHelper also takes care of drawing the child after other children if it is being
* dragged. This is done using child re-ordering mechanism. On platforms prior to L, this
* is
* achieved via {@link ViewGroup#getChildDrawingOrder(int, int)} and on L
* and after, it changes View's elevation value to be greater than all other children.)
*
* @param c The canvas which RecyclerView is drawing its children
* @param recyclerView The RecyclerView to which ItemTouchHelper is attached to
* @param viewHolder The ViewHolder which is being interacted by the User or it was
* interacted and simply animating to its original position
* @param dX The amount of horizontal displacement caused by user's action
* @param dY The amount of vertical displacement caused by user's action
* @param actionState The type of interaction on the View. Is either {@link
* #ACTION_STATE_DRAG} or {@link #ACTION_STATE_SWIPE}.
* @param isCurrentlyActive True if this view is currently being controlled by the user or
* false it is simply animating back to its original state.
* @see #onChildDrawOver(Canvas, RecyclerView, ViewHolder, float, float, int,
* boolean)
*/
public void onChildDrawOver(Canvas c, RecyclerView recyclerView,
ViewHolder viewHolder,
float dX, float dY, int actionState, boolean isCurrentlyActive) {
sUICallback.onDrawOver(c, recyclerView, viewHolder.itemView, dX, dY, actionState,
isCurrentlyActive);
}
/**
* Called by the ItemTouchHelper when user action finished on a ViewHolder and now the View
* will be animated to its final position.
* <p>
* Default implementation uses ItemAnimator's duration values. If
* <code>animationType</code> is {@link #ANIMATION_TYPE_DRAG}, it returns
* {@link RecyclerView.ItemAnimator#getMoveDuration()}, otherwise, it returns
* {@link RecyclerView.ItemAnimator#getRemoveDuration()}. If RecyclerView does not have
* any {@link RecyclerView.ItemAnimator} attached, this method returns
* {@code DEFAULT_DRAG_ANIMATION_DURATION} or {@code DEFAULT_SWIPE_ANIMATION_DURATION}
* depending on the animation type.
*
* @param recyclerView The RecyclerView to which the ItemTouchHelper is attached to.
* @param animationType The type of animation. Is one of {@link #ANIMATION_TYPE_DRAG},
* {@link #ANIMATION_TYPE_SWIPE_CANCEL} or
* {@link #ANIMATION_TYPE_SWIPE_SUCCESS}.
* @param animateDx The horizontal distance that the animation will offset
* @param animateDy The vertical distance that the animation will offset
* @return The duration for the animation
*/
public long getAnimationDuration(RecyclerView recyclerView, int animationType,
float animateDx, float animateDy) {
final RecyclerView.ItemAnimator itemAnimator = recyclerView.getItemAnimator();
if (itemAnimator == null) {
return animationType == ANIMATION_TYPE_DRAG ? DEFAULT_DRAG_ANIMATION_DURATION
: DEFAULT_SWIPE_ANIMATION_DURATION;
} else {
return animationType == ANIMATION_TYPE_DRAG ? itemAnimator.getMoveDuration()
: itemAnimator.getRemoveDuration();
}
}
/**
* Called by the ItemTouchHelper when user is dragging a view out of bounds.
* <p>
* You can override this method to decide how much RecyclerView should scroll in response
* to this action. Default implementation calculates a value based on the amount of View
* out of bounds and the time it spent there. The longer user keeps the View out of bounds,
* the faster the list will scroll. Similarly, the larger portion of the View is out of
* bounds, the faster the RecyclerView will scroll.
*
* @param recyclerView The RecyclerView instance to which ItemTouchHelper is
* attached to.
* @param viewSize The total size of the View in scroll direction, excluding
* item decorations.
* @param viewSizeOutOfBounds The total size of the View that is out of bounds. This value
* is negative if the View is dragged towards left or top edge.
* @param totalSize The total size of RecyclerView in the scroll direction.
* @param msSinceStartScroll The time passed since View is kept out of bounds.
* @return The amount that RecyclerView should scroll. Keep in mind that this value will
* be passed to {@link RecyclerView#scrollBy(int, int)} method.
*/
public int interpolateOutOfBoundsScroll(RecyclerView recyclerView,
int viewSize, int viewSizeOutOfBounds,
int totalSize, long msSinceStartScroll) {
final int maxScroll = getMaxDragScroll(recyclerView);
final int absOutOfBounds = Math.abs(viewSizeOutOfBounds);
final int direction = (int) Math.signum(viewSizeOutOfBounds);
// might be negative if other direction
float outOfBoundsRatio = Math.min(1f, 1f * absOutOfBounds / viewSize);
final int cappedScroll = (int) (direction * maxScroll
* sDragViewScrollCapInterpolator.getInterpolation(outOfBoundsRatio));
final float timeRatio;
if (msSinceStartScroll > DRAG_SCROLL_ACCELERATION_LIMIT_TIME_MS) {
timeRatio = 1f;
} else {
timeRatio = (float) msSinceStartScroll / DRAG_SCROLL_ACCELERATION_LIMIT_TIME_MS;
}
final int value = (int) (cappedScroll * sDragScrollInterpolator
.getInterpolation(timeRatio));
if (value == 0) {
return viewSizeOutOfBounds > 0 ? 1 : -1;
}
return value;
}
/**
* 通过viewHolder的item找到最上面显示的VIEW
* 自己写的
* @param viewHolder
* @return
*/
}
/**
* A simple wrapper to the default Callback which you can construct with drag and swipe
* directions and this class will handle the flag callbacks. You should still override onMove
* or
* onSwiped depending on your use case.
*
* <pre>
* ItemTouchHelper mIth = new ItemTouchHelper(
* new ItemTouchHelper.SimpleCallback(ItemTouchHelper.UP | ItemTouchHelper.DOWN,
* ItemTouchHelper.LEFT) {
* public abstract boolean onMove(RecyclerView recyclerView,
* ViewHolder viewHolder, ViewHolder target) {
* final int fromPos = viewHolder.getAdapterPosition();
* final int toPos = target.getAdapterPosition();
* // move item in `fromPos` to `toPos` in adapter.
* return true;// true if moved, false otherwise
* }
* public void onSwiped(ViewHolder viewHolder, int direction) {
* // remove from adapter
* }
* });
* </pre>
*/
public abstract static class SimpleCallback extends Callback {
private int mDefaultSwipeDirs;
private int mDefaultDragDirs;
/**
* Creates a Callback for the given drag and swipe allowance. These values serve as
* defaults
* and if you want to customize behavior per ViewHolder, you can override
* {@link #getSwipeDirs(RecyclerView, ViewHolder)}
* and / or {@link #getDragDirs(RecyclerView, ViewHolder)}.
*
* @param dragDirs Binary OR of direction flags in which the Views can be dragged. Must be
* composed of {@link #LEFT}, {@link #RIGHT}, {@link #START}, {@link
* #END},
* {@link #UP} and {@link #DOWN}.
* @param swipeDirs Binary OR of direction flags in which the Views can be swiped. Must be
* composed of {@link #LEFT}, {@link #RIGHT}, {@link #START}, {@link
* #END},
* {@link #UP} and {@link #DOWN}.
*/
public SimpleCallback(int dragDirs, int swipeDirs) {
mDefaultSwipeDirs = swipeDirs;
mDefaultDragDirs = dragDirs;
}
/**
* Updates the default swipe directions. For example, you can use this method to toggle
* certain directions depending on your use case.
*
* @param defaultSwipeDirs Binary OR of directions in which the ViewHolders can be swiped.
*/
public void setDefaultSwipeDirs(int defaultSwipeDirs) {
mDefaultSwipeDirs = defaultSwipeDirs;
}
/**
* Updates the default drag directions. For example, you can use this method to toggle
* certain directions depending on your use case.
*
* @param defaultDragDirs Binary OR of directions in which the ViewHolders can be dragged.
*/
public void setDefaultDragDirs(int defaultDragDirs) {
mDefaultDragDirs = defaultDragDirs;
}
/**
* Returns the swipe directions for the provided ViewHolder.
* Default implementation returns the swipe directions that was set via constructor or
* {@link #setDefaultSwipeDirs(int)}.
*
* @param recyclerView The RecyclerView to which the ItemTouchHelper is attached to.
* @param viewHolder The RecyclerView for which the swipe direction is queried.
* @return A binary OR of direction flags.
*/
public int getSwipeDirs(RecyclerView recyclerView, ViewHolder viewHolder) {
return mDefaultSwipeDirs;
}
/**
* Returns the drag directions for the provided ViewHolder.
* Default implementation returns the drag directions that was set via constructor or
* {@link #setDefaultDragDirs(int)}.
*
* @param recyclerView The RecyclerView to which the ItemTouchHelper is attached to.
* @param viewHolder The RecyclerView for which the swipe direction is queried.
* @return A binary OR of direction flags.
*/
public int getDragDirs(RecyclerView recyclerView, ViewHolder viewHolder) {
return mDefaultDragDirs;
}
@Override
public int getMovementFlags(RecyclerView recyclerView, ViewHolder viewHolder) {
return makeMovementFlags(getDragDirs(recyclerView, viewHolder),
getSwipeDirs(recyclerView, viewHolder));
}
}
private class ItemTouchHelperGestureListener extends GestureDetector.SimpleOnGestureListener {
/**
* Whether to execute code in response to the the invoking of
* {@link ItemTouchHelperGestureListener#onLongPress(MotionEvent)}.
* <p>
* It is necessary to control this here because
* {@link GestureDetector.SimpleOnGestureListener} can only be set on a
* {@link GestureDetector} in a GestureDetector's constructor, a GestureDetector will call
* onLongPress if an {@link MotionEvent#ACTION_DOWN} event is not followed by another event
* that would cancel it (like {@link MotionEvent#ACTION_UP} or
* {@link MotionEvent#ACTION_CANCEL}), the long press responding to the long press event
* needs to be cancellable to prevent unexpected behavior.
*
* @see #doNotReactToLongPress()
*/
private boolean mShouldReactToLongPress = true;
ItemTouchHelperGestureListener() {
}
/**
* Call to prevent executing code in response to
* {@link ItemTouchHelperGestureListener#onLongPress(MotionEvent)} being called.
*/
void doNotReactToLongPress() {
mShouldReactToLongPress = false;
}
@Override
public boolean onDown(MotionEvent e) {
return true;
}
@Override
public void onLongPress(MotionEvent e) {
if (!mShouldReactToLongPress) {
return;
}
View child = findChildView(e);
if (child != null) {
ViewHolder vh = mRecyclerView.getChildViewHolder(child);
if (vh != null) {
if (!mCallback.hasDragFlag(mRecyclerView, vh)) {
return;
}
int pointerId = e.getPointerId(0);
// Long press is deferred.
// Check w/ active pointer id to avoid selecting after motion
// event is canceled.
if (pointerId == mActivePointerId) {
final int index = e.findPointerIndex(mActivePointerId);
final float x = e.getX(index);
final float y = e.getY(index);
mInitialTouchX = x;
mInitialTouchY = y;
mDx = mDy = 0f;
Console.debug("OnGestureListener.onLongPress");
Console.debug("=>", "OnGestureListener.onLongPress", "void");
if (mCallback.isLongPressDragEnabled()) {
select(vh, ACTION_STATE_DRAG);
}
}
}
}
}
}
private static class RecoverAnimation implements Animator.AnimatorListener {
final float mStartDx;
final float mStartDy;
final float mTargetX;
final float mTargetY;
final ViewHolder mViewHolder;
final int mActionState;
private final ValueAnimator mValueAnimator;
final int mAnimationType;
public boolean mIsPendingCleanup;
float mX;
float mY;
// if user starts touching a recovering view, we put it into interaction mode again,
// instantly.
boolean mOverridden = false;
boolean mEnded = false;
private float mFraction;
RecoverAnimation(ViewHolder viewHolder, int animationType,
int actionState, float startDx, float startDy, float targetX, float targetY) {
mActionState = actionState;
mAnimationType = animationType;
mViewHolder = viewHolder;
mStartDx = startDx;
mStartDy = startDy;
mTargetX = targetX;
mTargetY = targetY;
mValueAnimator = ValueAnimator.ofFloat(0f, 1f);
mValueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
setFraction(animation.getAnimatedFraction());
}
});
mValueAnimator.setTarget(viewHolder.itemView);
mValueAnimator.addListener(this);
setFraction(0f);
}
public void setDuration(long duration) {
mValueAnimator.setDuration(duration);
}
public void start() {
mViewHolder.setIsRecyclable(false);
mValueAnimator.start();
}
public void cancel() {
mValueAnimator.cancel();
}
public void setFraction(float fraction) {
mFraction = fraction;
}
/**
* We run updates on onDraw method but use the fraction from animator callback.
* This way, we can sync translate x/y values w/ the animators to avoid one-off frames.
*/
public void update() {
if (mStartDx == mTargetX) {
mX = mViewHolder.itemView.getTranslationX();
} else {
mX = mStartDx + mFraction * (mTargetX - mStartDx);
}
if (mStartDy == mTargetY) {
mY = mViewHolder.itemView.getTranslationY();
} else {
mY = mStartDy + mFraction * (mTargetY - mStartDy);
}
Console.debug("getTranslationX", mFraction, mX, mY);
}
@Override
public void onAnimationStart(Animator animation) {
}
@Override
public void onAnimationEnd(Animator animation) {
if (!mEnded) {
mViewHolder.setIsRecyclable(true);
}
mEnded = true;
}
@Override
public void onAnimationCancel(Animator animation) {
setFraction(1f); //make sure we recover the view's state.
}
@Override
public void onAnimationRepeat(Animator animation) {
}
}
//分发按键事件给子控件
/**
* 找到自控控件
* 根据坐标
*
* @param e
*/
private void doChildClickEvent(MotionEvent e) {
if (mSelected == null)
return;
Console.debug("OnItemTouchHelper.doChildClickEvent");
View consumeEventView = mSelected.itemView;
if (consumeEventView instanceof ViewGroup)
consumeEventView = findConsumeView((ViewGroup) consumeEventView, e.getRawX(), e.getRawY());
if (consumeEventView != null)
consumeEventView.performClick();
}
private View findConsumeView(ViewGroup parent, float x, float y) {
for (int i = 0; i < parent.getChildCount(); i++) {
View child = parent.getChildAt(i);
if (child instanceof ViewGroup && child.getVisibility() == View.VISIBLE) {
View view = findConsumeView((ViewGroup) child, x, y);
if (view != null) {
return view;
}
} else {
if (isInBounds((int) x, (int) y, child)) {
return child;
}
}
}
if (isInBounds((int) x, (int) y, parent)) {
return parent;
}
return null;
}
private boolean isInBounds(int x, int y, View child) {
int[] location = new int[2];
child.getLocationOnScreen(location);
Rect rect = new Rect(location[0], location[1], location[0] + child.getWidth(), location[1] + child.getHeight());
if (rect.contains(x, y) && ViewCompat.hasOnClickListeners(child) &&
child.getVisibility() == View.VISIBLE) {
return true;
}
return false;
}
private void closeOpenedPreItem() {
final View view = getItemFrontView(mPreOpened);
if (mPreOpened == null || view == null) return;
Console.debug("closeOpenedPreItem");
ObjectAnimator objectAnimator = ObjectAnimator.ofFloat(view, "translationX", view.getTranslationX(), 0f);
objectAnimator.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationStart(Animator animation) {
super.onAnimationStart(animation);
mCallback.clearView(mRecyclerView, mPreOpened);
mPendingCleanup.remove(mPreOpened.itemView);
endRecoverAnimation(mPreOpened, true);
mPreOpened = mSelected;
}
@Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
}
});
objectAnimator.setInterpolator(new AccelerateDecelerateInterpolator());
objectAnimator.start();
}
public View getItemFrontView(ViewHolder viewHolder) {
if (viewHolder == null) return null;
if (viewHolder.itemView instanceof ViewGroup &&
((ViewGroup) viewHolder.itemView).getChildCount() > 1) {
ViewGroup viewGroup = (ViewGroup) viewHolder.itemView;
return viewGroup.getChildAt(viewGroup.getChildCount() - 1);
} else {
return viewHolder.itemView;
}
}
}
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