Android drawPath 实现QQ拖拽泡泡

本文转自：http://android.jobbole.com/84457/

这两天学习了使用Path绘制贝塞尔曲线相关，然后自己动手做了一个类似QQ未读消息可拖拽的小气泡，效果图如下：

最终效果图

接下来一步一步的实现整个过程。

基本原理

其实就是使用Path绘制三点的二次方贝塞尔曲线来完成那个妖娆的曲线的。然后根据触摸点不断绘制对应的圆形，根据距离的改变改变原始固定圆形的半径大小。最后就是松手后返回或者爆裂的实现。

Path介绍：

顾名思义，就是一个路径的意思，Path里面有很多的方法，本次设计主要用到的相关方法有

moveTo() 移动Path到一个指定的点
quadTo() 绘制二次贝塞尔曲线，接收两个点，第一个是控制弧度的点，第二个是终点。
lineTo() 就是连线
close() 闭合Path路径，
reset() 重置Path的相关设置

• Path入门热身：

Java

path.reset(); path.moveTo(200, 200); //第一个坐标是对应的控制的坐标，第二个坐标是终点坐标 path.quadTo(400, 250, 600, 200); canvas.drawPath(path, paint); canvas.translate(0, 200); //调用close,就会首尾闭合连接 path.close(); canvas.drawPath(path, paint);

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path.reset();

  path.moveTo(200, 200);

  //第一个坐标是对应的控制的坐标，第二个坐标是终点坐标

  path.quadTo(400, 250, 600, 200);

 

  canvas.drawPath(path, paint);

  canvas.translate(0, 200);

  //调用close,就会首尾闭合连接

  path.close();

  canvas.drawPath(path, paint);

记得不要在onDraw方法中new Path或者 Paint哟！

Path

具体实现拆分：

其实整个过程就是绘制了两个贝塞尔二次曲线的的闭合Path路径，然后在上面添加两个圆形。

原理图1

原理图2

• 闭合的Path 路径实现从左上点画二次贝塞尔曲线到左下点，左下点连线到右下点，右下点二次贝塞尔曲线到右上点，最后闭合一下!!
• 相关坐标的确定
  这是这次里面的难点之一，因为涉及到了数学里面的一个sin,cos,tan等等，我其实也忘完了，然后又脑补了一下，废话不多说，直接上图！！

为什么自己要亲自去画一下呢，因为画了你才知道，在360旋转的过程中，角标体系是有两套的，如果就使用一套来画的话，就画出现在旋转的过程中曲线重叠在一起的情况！

问题已经抛出来了，接下来直接看看代码实现！

角度确定

根据贴出来的原理图可以知道，我们可以使用起始圆心坐标和拖拽的圆心坐标，根据反正切函数来得到具体的弧度。

Java

int dy = Math.abs(CIRCLEY - startY);int dx = Math.abs(CIRCLEX - startX); angle = Math.atan(dy * 1.0 / dx);

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int dy = Math.abs(CIRCLEY - startY);

int dx = Math.abs(CIRCLEX - startX);

angle = Math.atan(dy * 1.0 / dx);

ok,这里的startX,Y就是移动过程中的坐标。angle就是得到的对应的弧度（角度）。

相关Path绘制

前面已经提到在旋转的过程中有两套坐标体系，一开始我也很纠结这个坐标体系要怎么确定，后面又恍然大悟，其实相当于就是一三象限正比例增长，二四象限，反比例增长。

Java

flag = (startY - CIRCLEY ) * (startX- CIRCLEX ) <= 0; //增加一个flag,用于判断使用哪种坐标体系。

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flag = (startY - CIRCLEY  ) * (startX- CIRCLEX ) <= 0;

//增加一个flag,用于判断使用哪种坐标体系。

最最重要的来了，绘制相关的Path路径！

Java

path.reset(); if (flag) { //第一个点 path.moveTo((float) (CIRCLEX - Math.sin(angle) * ORIGIN_RADIO), (float) (CIRCLEY - Math.cos(angle) * ORIGIN_RADIO)); path.quadTo((float) ((startX + CIRCLEX) * 0.5), (float) ((startY + CIRCLEY) * 0.5), (float) (startX - Math.sin(angle) * DRAG_RADIO), (float) (startY - Math.cos(angle) * DRAG_RADIO));path.lineTo((float) (startX + Math.sin(angle) * DRAG_RADIO), (float) (startY + Math.cos(angle) * DRAG_RADIO));path.quadTo((float) ((startX + CIRCLEX) * 0.5), (float) ((startY + CIRCLEY) * 0.5), (float) (CIRCLEX + Math.sin(angle) * ORIGIN_RADIO), (float) (CIRCLEY + Math.cos(angle) * ORIGIN_RADIO));path.close();canvas.drawPath(path, paint); } else { //第一个点 path.moveTo((float) (CIRCLEX - Math.sin(angle) * ORIGIN_RADIO), (float) (CIRCLEY + Math.cos(angle) * ORIGIN_RADIO)); path.quadTo((float) ((startX + CIRCLEX) * 0.5), (float) ((startY + CIRCLEY) * 0.5), (float) (startX - Math.sin(angle) * DRAG_RADIO), (float) (startY + Math.cos(angle) * DRAG_RADIO)); path.lineTo((float) (startX + Math.sin(angle) * DRAG_RADIO), (float) (startY - Math.cos(angle) * DRAG_RADIO)); path.quadTo((float) ((startX + CIRCLEX) * 0.5), (float) ((startY + CIRCLEY) * 0.5), (float) (CIRCLEX + Math.sin(angle) * ORIGIN_RADIO), (float) (CIRCLEY - Math.cos(angle) * ORIGIN_RADIO)); path.close(); canvas.drawPath(path, paint); }

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path.reset();

if (flag) {

     //第一个点

path.moveTo((float) (CIRCLEX - Math.sin(angle) * ORIGIN_RADIO), (float) (CIRCLEY - Math.cos(angle) * ORIGIN_RADIO));

 

path.quadTo((float) ((startX + CIRCLEX) * 0.5), (float) ((startY + CIRCLEY) * 0.5), (float) (startX - Math.sin(angle) * DRAG_RADIO), (float) (startY - Math.cos(angle) * DRAG_RADIO));

path.lineTo((float) (startX + Math.sin(angle) * DRAG_RADIO), (float) (startY + Math.cos(angle) * DRAG_RADIO));

 

path.quadTo((float) ((startX + CIRCLEX) * 0.5), (float) ((startY + CIRCLEY) * 0.5), (float) (CIRCLEX + Math.sin(angle) * ORIGIN_RADIO), (float) (CIRCLEY + Math.cos(angle) * ORIGIN_RADIO));

path.close();

canvas.drawPath(path, paint);

} else {

     //第一个点

     path.moveTo((float) (CIRCLEX - Math.sin(angle) * ORIGIN_RADIO), (float) (CIRCLEY + Math.cos(angle) * ORIGIN_RADIO));

 

     path.quadTo((float) ((startX + CIRCLEX) * 0.5), (float) ((startY + CIRCLEY) * 0.5), (float) (startX - Math.sin(angle) * DRAG_RADIO), (float) (startY + Math.cos(angle) * DRAG_RADIO));

     path.lineTo((float) (startX + Math.sin(angle) * DRAG_RADIO), (float) (startY - Math.cos(angle) * DRAG_RADIO));

 

     path.quadTo((float) ((startX + CIRCLEX) * 0.5), (float) ((startY + CIRCLEY) * 0.5), (float) (CIRCLEX + Math.sin(angle) * ORIGIN_RADIO), (float) (CIRCLEY - Math.cos(angle) * ORIGIN_RADIO));

     path.close();

     canvas.drawPath(path, paint);

}

这里的代码就是把图片上相关的数学公式Java化而已！

到这里，其实主要的工作就完成的差不多了！
接下来，设置paint 为填充的效果,最后再画两个圆

Java

paint.setStyle(Paint.Style.FILL) canvas.drawCircle(CIRCLEX, CIRCLEY, ORIGIN_RADIO, paint);//默认的 canvas.drawCircle(startX == 0 ? CIRCLEX : startX, startY == 0 ? CIRCLEY : startY, DRAG_RADIO, paint);//拖拽的

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paint.setStyle(Paint.Style.FILL)

canvas.drawCircle(CIRCLEX, CIRCLEY, ORIGIN_RADIO, paint);//默认的

canvas.drawCircle(startX == 0 ? CIRCLEX : startX, startY == 0 ? CIRCLEY : startY, DRAG_RADIO, paint);//拖拽的

就可以绘制出想要的效果了！

这里不得不再说说onTouch的处理！

Java

case MotionEvent.ACTION_DOWN://有事件先拦截再说！！ getParent().requestDisallowInterceptTouchEvent(true); CurrentState = STATE_IDLE; animSetXY.cancel(); startX = (int) ev.getX(); startY = (int) ev.getRawY(); break;

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case MotionEvent.ACTION_DOWN://有事件先拦截再说！！

            getParent().requestDisallowInterceptTouchEvent(true);

            CurrentState = STATE_IDLE;

            animSetXY.cancel();

            startX = (int) ev.getX();

            startY = (int) ev.getRawY();

            break;

处理一下事件分发的坑！

测量和布局

这样基本过得去了，但是我们的布局什么的还没有处理，math_parent是万万没法使用到具体项目当中去的！
测量的时候，如果发现不是精准模式，那么都手动去计算出需要的宽度和高度。

Java

@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { int modeWidth = MeasureSpec.getMode(widthMeasureSpec); int modeHeight = MeasureSpec.getMode(heightMeasureSpec); if (modeWidth == MeasureSpec.UNSPECIFIED || modeWidth == MeasureSpec.AT_MOST) { widthMeasureSpec = MeasureSpec.makeMeasureSpec(DEFAULT_RADIO * 2, MeasureSpec.EXACTLY); } if (modeHeight == MeasureSpec.UNSPECIFIED || modeHeight == MeasureSpec.AT_MOST) { heightMeasureSpec = MeasureSpec.makeMeasureSpec(DEFAULT_RADIO * 2, MeasureSpec.EXACTLY); } super.onMeasure(widthMeasureSpec, heightMeasureSpec);}

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@Override

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

 

    int modeWidth = MeasureSpec.getMode(widthMeasureSpec);

    int modeHeight = MeasureSpec.getMode(heightMeasureSpec);

    if (modeWidth == MeasureSpec.UNSPECIFIED || modeWidth == MeasureSpec.AT_MOST) {

        widthMeasureSpec = MeasureSpec.makeMeasureSpec(DEFAULT_RADIO * 2, MeasureSpec.EXACTLY);

    }

    if (modeHeight == MeasureSpec.UNSPECIFIED || modeHeight == MeasureSpec.AT_MOST) {

        heightMeasureSpec = MeasureSpec.makeMeasureSpec(DEFAULT_RADIO * 2, MeasureSpec.EXACTLY);

    }

    super.onMeasure(widthMeasureSpec, heightMeasureSpec);

}

然后在布局变化时，获取相关坐标，确定初始圆心坐标：

Java

@Overrideprotected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); CIRCLEX = (int) ((w) * 0.5 + 0.5); CIRCLEY = (int) ((h) * 0.5 + 0.5);}

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@Override

protected void onSizeChanged(int w, int h, int oldw, int oldh) {

    super.onSizeChanged(w, h, oldw, oldh);

    CIRCLEX = (int) ((w) * 0.5 + 0.5);

    CIRCLEY = (int) ((h) * 0.5 + 0.5);

}

然后清单文件里面就可以这样配置了：

Java

<com.lovejjfg.circle.DragBubbleView android:id=”@+id/dbv” android:layout_width=”wrap_content” android:layout_height=”wrap_content” android:layout_gravity=”center”/>

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<com.lovejjfg.circle.DragBubbleView

    android:id=“@+id/dbv”

    android:layout_width=“wrap_content”

    android:layout_height=“wrap_content”

    android:layout_gravity=“center”/>

这样之后，又会出现一个问题，那就是wrap_content 之后，这个View能绘制的区域只有自身那么大了，拖拽了都看不见了！这个坑怎么办呢，其实很简单，父布局加上android:clipChildren="false" 的属性！
这个坑也算是解决了！！

相关状态的确定

我们是不希望它可以无限的拖拽的，就是有一个拖拽的最远距离，还有就是放手后的返回，爆裂。那么对应的，这里需要确定几种状态：

Java

private final static int STATE_IDLE = 1;//静止的状态 private final static int STATE_DRAG_NORMAL = 2;//正在拖拽的状态 private final static int STATE_DRAG_BREAK = 3;//断裂后的拖拽状态 private final static int STATE_UP_BREAK = 4;//放手后的爆裂的状态 private final static int STATE_UP_BACK = 5;//放手后的没有断裂的返回的状态 private final static int STATE_UP_DRAG_BREAK_BACK = 6;//拖拽断裂又返回的状态 private int CurrentState = STATE_IDLE;private int MIN_RADIO = (int) (ORIGIN_RADIO * 0.4);//最小半径 private int MAXDISTANCE = (int) (MIN_RADIO * 13);//最远的拖拽距离

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private final static int STATE_IDLE = 1;//静止的状态

    private final static int STATE_DRAG_NORMAL = 2;//正在拖拽的状态

    private final static int STATE_DRAG_BREAK = 3;//断裂后的拖拽状态

    private final static int STATE_UP_BREAK = 4;//放手后的爆裂的状态

    private final static int STATE_UP_BACK = 5;//放手后的没有断裂的返回的状态

    private final static int STATE_UP_DRAG_BREAK_BACK = 6;//拖拽断裂又返回的状态

    private int CurrentState = STATE_IDLE;

 

private int MIN_RADIO = (int) (ORIGIN_RADIO * 0.4);//最小半径

    private int MAXDISTANCE = (int) (MIN_RADIO * 13);//最远的拖拽距离

确定好这些之后，在move的时候，就要去做相关判断了：

Java

case MotionEvent.ACTION_MOVE://移动的时候 startX = (int) ev.getX(); startY = (int) ev.getY(); updatePath(); invalidate(); break;private void updatePath() { int dy = Math.abs(CIRCLEY - startY); int dx = Math.abs(CIRCLEX - startX); double dis = Math.sqrt(dy * dy + dx * dx); if (dis <= MAXDISTANCE) {//增加的情况，原始半径减小 if (CurrentState == STATE_DRAG_BREAK || CurrentState == STATE_UP_DRAG_BREAK_BACK) { CurrentState = STATE_UP_DRAG_BREAK_BACK; } else { CurrentState = STATE_DRAG_NORMAL; } ORIGIN_RADIO = (int) (DEFAULT_RADIO - (dis / MAXDISTANCE) * (DEFAULT_RADIO - MIN_RADIO)); Log.e(TAG, “distance: ” + (int) ((1 - dis / MAXDISTANCE) * MIN_RADIO)); Log.i(TAG, “distance: ” + ORIGIN_RADIO); } else { CurrentState = STATE_DRAG_BREAK; }// distance = dis; flag = (startY - CIRCLEY) * (startX - CIRCLEX) <= 0; Log.i(“TAG”, “updatePath: ” + flag); angle = Math.atan(dy * 1.0 / dx);}

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case MotionEvent.ACTION_MOVE://移动的时候

            startX = (int) ev.getX();

            startY = (int) ev.getY();

 

            updatePath();

            invalidate();

            break;

 

private void updatePath() {

    int dy = Math.abs(CIRCLEY - startY);

    int dx = Math.abs(CIRCLEX - startX);

 

    double dis = Math.sqrt(dy * dy + dx * dx);

    if (dis <= MAXDISTANCE) {//增加的情况，原始半径减小

        if (CurrentState == STATE_DRAG_BREAK || CurrentState == STATE_UP_DRAG_BREAK_BACK) {

            CurrentState = STATE_UP_DRAG_BREAK_BACK;

        } else {

            CurrentState = STATE_DRAG_NORMAL;

        }

        ORIGIN_RADIO = (int) (DEFAULT_RADIO - (dis / MAXDISTANCE) * (DEFAULT_RADIO - MIN_RADIO));

        Log.e(TAG, “distance: “ + (int) ((1 - dis / MAXDISTANCE) * MIN_RADIO));

        Log.i(TAG, “distance: “ + ORIGIN_RADIO);

    } else {

        CurrentState = STATE_DRAG_BREAK;

    }

//        distance = dis;

    flag = (startY - CIRCLEY) * (startX - CIRCLEX) <= 0;

    Log.i(“TAG”, “updatePath: “ + flag);

    angle = Math.atan(dy * 1.0 / dx);

}

updatePath() 的方法之前已经看过部分了，这次的就是完整的。
这里做的事就是根据拖拽的距离更改相关的状态，并根据百分比来修改原始圆形的半径大小。还有就是之前介绍的确定相关的弧度！

最后放手的时候：

Java

case MotionEvent.ACTION_UP: if (CurrentState == STATE_DRAG_NORMAL) { CurrentState = STATE_UP_BACK; valueX.setIntValues(startX, CIRCLEX); valueY.setIntValues(startY, CIRCLEY); animSetXY.start(); } else if (CurrentState == STATE_DRAG_BREAK) { CurrentState = STATE_UP_BREAK; invalidate(); } else { CurrentState = STATE_UP_DRAG_BREAK_BACK; valueX.setIntValues(startX, CIRCLEX); valueY.setIntValues(startY, CIRCLEY); animSetXY.start(); } break;

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case MotionEvent.ACTION_UP:

            if (CurrentState == STATE_DRAG_NORMAL) {

                CurrentState = STATE_UP_BACK;

                valueX.setIntValues(startX, CIRCLEX);

                valueY.setIntValues(startY, CIRCLEY);

                animSetXY.start();

            } else if (CurrentState == STATE_DRAG_BREAK) {

                CurrentState = STATE_UP_BREAK;

                invalidate();

            } else {

                CurrentState = STATE_UP_DRAG_BREAK_BACK;

                valueX.setIntValues(startX, CIRCLEX);

                valueY.setIntValues(startY, CIRCLEY);

                animSetXY.start();

            }

            break;

自动返回这里使用到的 ValueAnimator，

Java

animSetXY = new AnimatorSet(); valueX = ValueAnimator.ofInt(startX, CIRCLEX); valueY = ValueAnimator.ofInt(startY, CIRCLEY); animSetXY.playTogether(valueX, valueY); valueX.setDuration(500); valueY.setDuration(500); valueX.setInterpolator(new OvershootInterpolator()); valueY.setInterpolator(new OvershootInterpolator()); valueX.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { @Override public void onAnimationUpdate(ValueAnimator animation) { startX = (int) animation.getAnimatedValue(); Log.e(TAG, “onAnimationUpdate-startX: ” + startX); invalidate(); } }); valueY.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { @Override public void onAnimationUpdate(ValueAnimator animation) { startY = (int) animation.getAnimatedValue(); Log.e(TAG, “onAnimationUpdate-startY: ” + startY); invalidate(); } });

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animSetXY = new AnimatorSet();

 

    valueX = ValueAnimator.ofInt(startX, CIRCLEX);

    valueY = ValueAnimator.ofInt(startY, CIRCLEY);

    animSetXY.playTogether(valueX, valueY);

    valueX.setDuration(500);

    valueY.setDuration(500);

    valueX.setInterpolator(new OvershootInterpolator());

    valueY.setInterpolator(new OvershootInterpolator());

    valueX.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {

        @Override

        public void onAnimationUpdate(ValueAnimator animation) {

            startX = (int) animation.getAnimatedValue();

            Log.e(TAG, “onAnimationUpdate-startX: “ + startX);

            invalidate();

        }

 

    });

    valueY.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {

        @Override

        public void onAnimationUpdate(ValueAnimator animation) {

            startY = (int) animation.getAnimatedValue();

            Log.e(TAG, “onAnimationUpdate-startY: “ + startY);

            invalidate();

 

        }

    });

最后在看看完整的onDraw方法吧！

Java

@Overrideprotected void onDraw(Canvas canvas) { switch (CurrentState) { case STATE_IDLE://空闲状态，就画默认的圆 if (showCircle) { canvas.drawCircle(CIRCLEX, CIRCLEY, ORIGIN_RADIO, paint);//默认的 } break; case STATE_UP_BACK://执行返回的动画 case STATE_DRAG_NORMAL://拖拽状态 画贝塞尔曲线和两个圆 path.reset(); if (flag) { //第一个点 path.moveTo((float) (CIRCLEX - Math.sin(angle) * ORIGIN_RADIO), (float) (CIRCLEY - Math.cos(angle) * ORIGIN_RADIO)); path.quadTo((float) ((startX + CIRCLEX) * 0.5), (float) ((startY + CIRCLEY) * 0.5), (float) (startX - Math.sin(angle) * DRAG_RADIO), (float) (startY - Math.cos(angle) * DRAG_RADIO)); path.lineTo((float) (startX + Math.sin(angle) * DRAG_RADIO), (float) (startY + Math.cos(angle) * DRAG_RADIO)); path.quadTo((float) ((startX + CIRCLEX) * 0.5), (float) ((startY + CIRCLEY) * 0.5), (float) (CIRCLEX + Math.sin(angle) * ORIGIN_RADIO), (float) (CIRCLEY + Math.cos(angle) * ORIGIN_RADIO)); path.close(); canvas.drawPath(path, paint); } else { //第一个点 path.moveTo((float) (CIRCLEX - Math.sin(angle) * ORIGIN_RADIO), (float) (CIRCLEY + Math.cos(angle) * ORIGIN_RADIO)); path.quadTo((float) ((startX + CIRCLEX) * 0.5), (float) ((startY + CIRCLEY) * 0.5), (float) (startX - Math.sin(angle) * DRAG_RADIO), (float) (startY + Math.cos(angle) * DRAG_RADIO)); path.lineTo((float) (startX + Math.sin(angle) * DRAG_RADIO), (float) (startY - Math.cos(angle) * DRAG_RADIO)); path.quadTo((float) ((startX + CIRCLEX) * 0.5), (float) ((startY + CIRCLEY) * 0.5), (float) (CIRCLEX + Math.sin(angle) * ORIGIN_RADIO), (float) (CIRCLEY - Math.cos(angle) * ORIGIN_RADIO)); path.close(); canvas.drawPath(path, paint); } if (showCircle) { canvas.drawCircle(CIRCLEX, CIRCLEY, ORIGIN_RADIO, paint);//默认的 canvas.drawCircle(startX == 0 ? CIRCLEX : startX, startY == 0 ? CIRCLEY : startY, DRAG_RADIO, paint);//拖拽的 } break; case STATE_DRAG_BREAK://拖拽到了上限，画拖拽的圆: case STATE_UP_DRAG_BREAK_BACK: if (showCircle) { canvas.drawCircle(startX == 0 ? CIRCLEX : startX, startY == 0 ? CIRCLEY : startY, DRAG_RADIO, paint);//拖拽的 } break; case STATE_UP_BREAK://画出爆裂的效果 canvas.drawCircle(startX - 25, startY - 25, 10, circlePaint); canvas.drawCircle(startX + 25, startY + 25, 10, circlePaint); canvas.drawCircle(startX, startY - 25, 10, circlePaint); canvas.drawCircle(startX, startY, 18, circlePaint); canvas.drawCircle(startX - 25, startY, 10, circlePaint); break; }}

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@Override

protected void onDraw(Canvas canvas) {

    switch (CurrentState) {

        case STATE_IDLE://空闲状态，就画默认的圆

            if (showCircle) {

                canvas.drawCircle(CIRCLEX, CIRCLEY, ORIGIN_RADIO, paint);//默认的

            }

            break;

        case STATE_UP_BACK://执行返回的动画

        case STATE_DRAG_NORMAL://拖拽状态 画贝塞尔曲线和两个圆

            path.reset();

            if (flag) {

                //第一个点

                path.moveTo((float) (CIRCLEX - Math.sin(angle) * ORIGIN_RADIO), (float) (CIRCLEY - Math.cos(angle) * ORIGIN_RADIO));

 

                path.quadTo((float) ((startX + CIRCLEX) * 0.5), (float) ((startY + CIRCLEY) * 0.5), (float) (startX - Math.sin(angle) * DRAG_RADIO), (float) (startY - Math.cos(angle) * DRAG_RADIO));

                path.lineTo((float) (startX + Math.sin(angle) * DRAG_RADIO), (float) (startY + Math.cos(angle) * DRAG_RADIO));

 

                path.quadTo((float) ((startX + CIRCLEX) * 0.5), (float) ((startY + CIRCLEY) * 0.5), (float) (CIRCLEX + Math.sin(angle) * ORIGIN_RADIO), (float) (CIRCLEY + Math.cos(angle) * ORIGIN_RADIO));

                path.close();

                canvas.drawPath(path, paint);

            } else {

                //第一个点

                path.moveTo((float) (CIRCLEX - Math.sin(angle) * ORIGIN_RADIO), (float) (CIRCLEY + Math.cos(angle) * ORIGIN_RADIO));

 

                path.quadTo((float) ((startX + CIRCLEX) * 0.5), (float) ((startY + CIRCLEY) * 0.5), (float) (startX - Math.sin(angle) * DRAG_RADIO), (float) (startY + Math.cos(angle) * DRAG_RADIO));

                path.lineTo((float) (startX + Math.sin(angle) * DRAG_RADIO), (float) (startY - Math.cos(angle) * DRAG_RADIO));

 

                path.quadTo((float) ((startX + CIRCLEX) * 0.5), (float) ((startY + CIRCLEY) * 0.5), (float) (CIRCLEX + Math.sin(angle) * ORIGIN_RADIO), (float) (CIRCLEY - Math.cos(angle) * ORIGIN_RADIO));

                path.close();

                canvas.drawPath(path, paint);

            }

            if (showCircle) {

                canvas.drawCircle(CIRCLEX, CIRCLEY, ORIGIN_RADIO, paint);//默认的

                canvas.drawCircle(startX == 0 ? CIRCLEX : startX, startY == 0 ? CIRCLEY : startY, DRAG_RADIO, paint);//拖拽的

            }

            break;

 

        case STATE_DRAG_BREAK://拖拽到了上限，画拖拽的圆:

        case STATE_UP_DRAG_BREAK_BACK:

            if (showCircle) {

                canvas.drawCircle(startX == 0 ? CIRCLEX : startX, startY == 0 ? CIRCLEY : startY, DRAG_RADIO, paint);//拖拽的

            }

            break;

 

        case STATE_UP_BREAK://画出爆裂的效果

            canvas.drawCircle(startX - 25, startY - 25, 10, circlePaint);

            canvas.drawCircle(startX + 25, startY + 25, 10, circlePaint);

            canvas.drawCircle(startX, startY - 25, 10, circlePaint);

            canvas.drawCircle(startX, startY, 18, circlePaint);

            canvas.drawCircle(startX - 25, startY, 10, circlePaint);

            break;

 

    }

 

 

}

到这里，成品就出来了！！

总结：

1、确定默认圆形的坐标；
2、根据move的情况，实时获取最新的坐标，根据移动的距离（确定出角度），更新相关的状态，画出相关的Path路径。超出上限，不再画Path路径。
3、松手时，根据相关的状态，要么带Path路径执行动画返回，要么不带Path路径直接返回，要么直接爆裂！

下一篇 Android 自定义View 跳动的水果和文字

相关源码请移步Github，喜欢就请Start或者 fork一下吧，有问题欢迎留言或者issue。。