c.推导公式求解x和y。
辅助线我就不画了，我直接给出推导公式
转换成java代码如下
float tagX = (float) (Math.sin(Math.toRadians(60)) * mRadius
/ Math.cos(Math.toRadians(30 - swipeAgenl))
- Math.sin(Math.toRadians(60 - swipeAgenl)));
float tagY = (float) (Math.sin(Math.toRadians(60)) * mRadius
/ Math.cos(Math.toRadians(30 - swipeAgenl))
- Math.cos(Math.toRadians(60 - swipeAgenl))) - mRadius;
运行看下效果是不是符合预期
4.圆弧
点(0,-R)到(√3/2/R,R/2)点与圆相交处会有个圆弧。这里利用Path.addArc或者canvas.drawArc方法都可以绘制。所传参方式有两种，其实本质都是传入一个矩形然后在矩形框内绘制一个圆弧。
Path.java
public void addArc(RectF oval, float startAngle, float sweepAngle) {
addArc(oval.left, oval.top, oval.right, oval.bottom, startAngle, sweepAngle);
}
Canvas.java
public void drawArc(@NonNull RectF oval, float startAngle, float sweepAngle, boolean useCenter,
@NonNull Paint paint) {
drawArc(oval.left, oval.top, oval.right, oval.bottom, startAngle, sweepAngle, useCenter,
paint);
}
startAngle 为开始的角度，sweepAngle为圆弧滑过的角度。代码如下:
RectF oval = new RectF(-mRadius, -mRadius, mRadius, mRadius);
mPaint.setStyle(Paint.Style.FILL);
path.addArc(oval, -90, 60);
5.看看效果
画出了一个，那么6个就很好画，为了方面观察效果，我把每个都整成了不同颜色，方便大家看。
咦，不对劲呀，和我预想的不一样。我们可以再看看UI做的效果图。抛开图形旋转角度的因素，可以观察到，图形是随着时间的变化，红色边线一直拉长而形成的。最大长度是R，最小长度是0，或者你设置任意初始值，还有一点要注意，在红线延伸的过程中，夹角始终是60度。
6.重新计算
依旧是正弦函数，余弦函数，算出点在红线上的位置。
float L1 = (float) Math.sqrt(Math.pow(mRadius, 2.0) -
Math.pow(Math.sin(Math.toRadians(60)) * a, 2.0));
float consL1 = L1 / mRadius;
float sinL1 = (float) Math.sin(Math.toRadians(60)) * a / mRadius;
float L = (float) (L1 + Math.sin(Math.toRadians(30)) * a);
float tagX = L * sinL;
float tagY = L * consL - mRadius;
7.大功告成
/**
- @authoer create by markfrain
- @github https://github.com/furuiCQ
- 高怀见物理 和气得天真
- 时间: 4/28/21
- 描述: ShootView
*/
public class ShootView extends View {
private static final int DEGREE_60 = 60;
private final Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
private final RectF mBounds = new RectF();
private int mRadius;
private int mCenterX;
private int mCenterY;
private ValueAnimator mPlayAnimator;
private float swipeAgenl = mRadius;//延伸的距离
private float mShootLineTotalRotateAngle;//旋转角度
private ValueAnimator mPreShootLineTotalRotateAnimator;
private float padding = 20;
private ValueAnimator paddingAnimator;
private float fix = 4;
private ValueAnimator fixAnimator;
private static final float SHOOT_LINE_ROTATE_END_RADIANS = (float) (Math.PI / 6.0);//旋转结束弧度
private static final float SHOOT_LINE_ROTATE_START_RADIANS = (float) (Math.PI / 2.0);//旋转开始弧度
private static final float SHOOT_LINE_ROTATE_START_DEGREE =
(float) Math.toDegrees(SHOOT_LINE_ROTATE_END_RADIANS);//旋转开始角度
private static final int PRE_SHOOT_LINE_TOTAL_ROTATE_DURATION = 1000;
public static final Property<ShootView, Float> SHOOT_LINE_TOTAL_ROTATE_DEGREE =
new Property<ShootView, Float>(Float.class, null) {
@Override
public Float get(ShootView object) {
return object.mShootLineTotalRotateAngle;
}
@Override
public void set(ShootView object, Float value) {
object.mShootLineTotalRotateAngle = value;
object.invalidate();
}
};
public ShootView(Context context) {
this(context, null);
}
public ShootView(Context context, @Nullable AttributeSet attrs) {
this(context, attrs, 0);
}
public ShootView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeWidth(5);
mPaint.setColor(Color.parseColor("#ffc6c6c6"));
paddingAnimator = ValueAnimator.ofFloat(20, 0);
paddingAnimator.setInterpolator(new LinearInterpolator());
paddingAnimator.setDuration(PRE_SHOOT_LINE_TOTAL_ROTATE_DURATION);
paddingAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
padding = (float) animation.getAnimatedValue();
invalidate();
}
});
fixAnimator = ValueAnimator.ofFloat(4, 0);
fixAnimator.setInterpolator(new LinearInterpolator());
fixAnimator.setDuration(1200);
fixAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
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erride
public void onAnimationUpdate(ValueAnimator animation) {
fix = (float) animation.getAnimatedValue();
invalidate();
}
});
mPreShootLineTotalRotateAnimator =
ValueAnimator.ofFloat(-(SHOOT_LINE_ROTATE_START_DEGREE / 2.0f) - 240.0f,
-(SHOOT_LINE_ROTATE_START_DEGREE / 2.0f) - 120.0f);
mPreShootLineTotalRotateAnimator.setInterpolator(new LinearInterpolator());
mPreShootLineTotalRotateAnimator.setDuration(PRE_SHOOT_LINE_TOTAL_ROTATE_DURATION);
mPreShootLineTotalRotateAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
mShootLineTotalRotateAngle = (float) animation.getAnimatedValue();
invalidate();
}
});
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
// drawTest(canvas);
drawArc(canvas);
drawCircle(canvas);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
mBounds.set(0 + getPaddingLeft(), 0 + getPaddingTop(), w - getPaddingRight(),
h - getPaddingBottom());
mRadius = (int) (Math.min(mBounds.width(), mBounds.height()) / 2);
mCenterX = (int) mBounds.centerX();
mCenterY = (int) mBounds.centerY();
swipeAgenl = mRadius * 2 / 3f;
}
float mStartX;
float mStartY;
int colors[] = {Color.RED, Color.GREEN, Color.YELLOW, Color.MAGENTA, Color.CYAN, Color.GRAY};
private void drawTest(Canvas canvas) {
drawCircle(canvas);
canvas.save();
canvas.translate(mCenterX, mCenterY);
int i = 0;
canvas.save();
canvas.rotate(-DEGREE_60 * i);
Path path = new Path();
float stopX = (float) Math.sqrt(3) * mRadius / 2f;
float stopY = -mRadius / 2f;
canvas.drawLine(0, -mRadius, stopX, stopY, mPaint);
mPaint.setColor(Color.RED);
canvas.drawPoint(stopX, stopY, mPaint);
mPaint.setColor(Color.RED);
//canvas.drawLine(0, 0, stopX, stopY, mPaint);
RectF oval = new RectF(-mRadius, -mRadius, mRadius, mRadius);
RectF rectF = new RectF(-mRadius, -2 * mRadius, mRadius, 0);
mPaint.setStyle(Paint.Style.FILL);
path.addArc(oval, -90, 60);
//计算直接点的
float tagX = (float) (Math.sin(Math.toRadians(60)) * mRadius / Math.cos(Math.toRadians(30 - swipeAgenl)) * Math.sin(Math.toRadians(60 - swipeAgenl)));
float tagY = (float) (Math.sin(Math.toRadians(60)) * mRadius / Math.cos(Math.toRadians(30 - swipeAgenl)) * Math.cos(Math.toRadians(60 - swipeAgenl))) - mRadius;
// float tagX = Math.sqrt(Math.pow(mRadius,2.0) - Math.pow(Math.sin(Math.toRadians(60) * swipeAgenl), 2.0));
// float L = (float) Math.sqrt(Math.pow(mRadius, 2.0) - Math.pow(Math.sin(Math.toRadians(60)) * swipeAgenl, 2.0));
// float consL = L / mRadius;
// float sinL = (float) Math.sin(Math.toRadians(60)) * swipeAgenl / mRadius;
// float LL = (float) (L + Math.sin(Math.toRadians(30)) * swipeAgenl);
//
// float tagX = LL * sinL;
// float tagY = LL * consL - mRadius;
canvas.drawPoint(tagX, tagY, mPaint);
// path.moveTo(stopX, stopY);
// path.lineTo(tagX, tagY);
// path.lineTo(0, -mRadius);
canvas.drawPath(path, mPaint);
// }
}
private void drawArc(Canvas canvas) {
canvas.save();
canvas.translate(mCenterX, mCenterY);
canvas.rotate(mShootLineTotalRotateAngle);
for (int i = 0; i < 6; i++) {
canvas.save();
canvas.rotate(-DEGREE_60 * i);
Path path = new Path();
mPaint.setColor(colors[i]);
RectF oval = new RectF(-mRadius, -mRadius, mRadius, mRadius);
mPaint.setStyle(Paint.Style.FILL);
// mRadius- padding
double asin = Math.toDegrees(Math.asin((mRadius - padding) / mRadius / 2)) * 2;
path.addArc(oval, -90, (float) asin);
;
mPaint.setColor(colors[i]);
RectF oval = new RectF(-mRadius, -mRadius, mRadius, mRadius);
mPaint.setStyle(Paint.Style.FILL);
// mRadius- padding
double asin = Math.toDegrees(Math.asin((mRadius - padding) / mRadius / 2)) * 2;
path.addArc(oval, -90, (float) asin);