[移动开发]实现长图片自动循环滚动效果，android实战开发-天气预报PPT

public ViewHolder(final View itemView) {
super(itemView);
item_bg = itemView.findViewById(R.id.item_bg);
}

}

}

2.控制smoothScrollToPosition的滑动速度

参考RecyclerView调用smoothScrollToPosition() 控制滑动速度，修改MILLISECONDS_PER_INCH的值即可

/**

• 更改RecyclerView滚动的速度
  */
  public class ScollLinearLayoutManager extends LinearLayoutManager {
  private float MILLISECONDS_PER_INCH = 25f; //修改可以改变数据,越大速度越慢
  private Context contxt;

public ScollLinearLayoutManager(Context context) {
super(context);
this.contxt = context;
}

@Override
public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {
LinearSmoothScroller linearSmoothScroller =
new LinearSmoothScroller(recyclerView.getContext()) {
@Override
public PointF computeScrollVectorForPosition(int targetPosition) {
return ScollLinearLayoutManager.this
.computeScrollVectorForPosition(targetPosition);
}

@Override
protected float calculateSpeedPerPixel
(DisplayMetrics displayMetrics) {
return MILLISECONDS_PER_INCH / displayMetrics.density;
//返回滑动一个pixel需要多少毫秒
}

};
linearSmoothScroller.setTargetPosition(position);
startSmoothScroll(linearSmoothScroller);
}

//可以用来设置速度
public void setSpeedSlow(float x) {
//自己在这里用density去乘，希望不同分辨率设备上滑动速度相同
//0.3f是自己估摸的一个值，可以根据不同需求自己修改
MILLISECONDS_PER_INCH = contxt.getResources().getDisplayMetrics().density * 0.3f + (x);
}

}

3.图片宽度充满屏幕、高度按图片原始宽高比例自适应

@SuppressLint(“AppCompatCustomView”)
public class FitImageView extends ImageView {

public FitImageView(Context context) {
super(context);
}

public FitImageView(Context context, AttributeSet attrs) {
super(context, attrs);
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec){
Drawable drawable = getDrawable();

if(drawable!=null){
int width = MeasureSpec.getSize(widthMeasureSpec);
int height = (int) Math.ceil((float) width * (float) drawable.getIntrinsicHeight() / (float) drawable.getIntrinsicWidth());
setMeasuredDimension(width, height);
}else{
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}

}

4.这里需要注意的是、Item的根布局android:layout_height=“wrap_content”，否则图片高度会受限

<android.support.constraint.ConstraintLayout xmlns:android=“http://schemas.android.com/apk/res/android”
android:layout_width=“match_parent”
android:layout_height=“wrap_content”>

<com.next.scrollimagedemo.view.FitImageView
android:id="@+id/item_bg"
android:layout_width=“match_parent”
android:layout_height=“wrap_content”
android:src="@mipmap/ww1" />

</android.support.constraint.ConstraintLayout>

5. 使RecyclerView不能手指触碰滑动

加层View屏蔽掉事件就好了

<android.support.constraint.ConstraintLayout xmlns:android=“http://schemas.android.com/apk/res/android”
xmlns:app=“http://schemas.android.com/apk/res-auto”
xmlns:tools=“http://schemas.android.com/tools”
android:layout_width=“match_parent”
android:layout_height=“match_parent”
tools:context=".MainActivity">

<android.support.v7.widget.RecyclerView
android:id="@+id/mRecyclerView"
android:layout_width=“match_parent”
android:layout_height=“match_parent”></android.support.v7.widget.RecyclerView>

<TextView
android:layout_width=“match_parent”
android:layout_height=“match_parent”
android:background="#80000000"