JelloToggle extends FrameLayout

首先调用onMeasure方法计算计算宽高和限制距离等操作

mJelloRect.set(getMeasuredWidth() - mJelloSize, 0, getMeasuredWidth() + mDragLimit,

        mJelloSize);但是为什么要右边出去一点呢

mCheckedDrawable.setBounds(mJelloRect.left, mJelloRect.top, mJelloRect.left + mJelloSize,
        mJelloSize);
mOnCheckDrawable.setBounds(mJelloRect.left, mJelloRect.top, mJelloRect.left + mJelloSize,
        mJelloSize);
mUnCheckedDrawable.setBounds(mJelloRect.left, mJelloRect.top, mJelloRect.left + mJelloSize,
        mJelloSize)设置图片的位置

然后执行private void calPath() {

    mJelloPath.rewind();
    mJelloPath.moveTo(mJelloRect.right, 0);
    mJelloPath.lineTo(mJelloRect.left, 0);
    mJelloPath.cubicTo(mJelloRect.left, mJelloSize / 2, mJelloRect.left + mJelloOffset -
                    mJelloSize / 3, mJelloSize * 3 / 4,
            mJelloRect.left, mJelloSize);
    mJelloPath.lineTo(mJelloRect.right, mJelloRect.bottom);
    mJelloPath.close();
}

画图。有贝塞尔曲线点的路径，在下面 dispatchDraw方法中有调用

@Override
protected void dispatchDraw(Canvas canvas) {
    canvas.save();
    canvas.translate(mScrollOffset, 0);
    super.dispatchDraw(canvas);
    canvas.restore();
    canvas.save();
    canvas.translate(mScrollOffset / 2, 0);
    canvas.drawPath(mJelloPath, mJelloPaint);
    mDrawable.draw(canvas);
    canvas.restore();
}

这是一个画子view的类， canvas.save(); canvas.restore();配对使用，进行缩放和位移的时候，一个是画textview，一个是画我们的view，

@Override
public boolean onTouchEvent(MotionEvent event) {
    boolean ret = true;
    switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            if (!mScroller.isFinished()) {
                mScroller.forceFinished(true);
            }
            mTouchStartX = (int) event.getX();
            mDrawable = mOnCheckDrawable;
            break;
        case MotionEvent.ACTION_MOVE:
            int dragLen = Math.min(0, (int) event.getX() - mTouchStartX);
            mScrollOffset = Math.max(-mDragLimit, dragLen);
            mJelloOffset = dragLen;
            calPath();
            postInvalidate();
            break;
        case MotionEvent.ACTION_UP:
            if (mScrollOffset < 0) {
                mScroller.startScroll(mScrollOffset, 0, -mScrollOffset, 0);
                mJelloMax = mJelloOffset;
                if (mJelloOffset <= -mDragLimit) {
                    mChecked = !mChecked;
                    if (mListener != null) {
                        mListener.onCheckedChange(mChecked);
                    }
                }
                setJelloState();
                postInvalidate();
                startJello();
            }
            break;
    }

    return ret;
}

使用finish，移动的时候，记录整个view和自己的view移动的距离，进行画图用

mScroller.startScroll(mScrollOffset, 0, -mScrollOffset, 0);对自己进行回弹

private Runnable mJelloRunnable = new Runnable() {
    @Override
    public void run() {
        long playTime = AnimationUtils.currentAnimationTimeMillis() - mStartTime;
        if (playTime < mDuration) {
            float fraction = playTime / (float) mDuration;
            mJelloOffset = (int) (mJelloMax * (1 - mInterpolator.getInterpolation
                    (fraction)));
            calPath();
            ViewCompat.postInvalidateOnAnimation(JelloToggle.this);
            post(this);
        } else {
            mJelloOffset = 0;
            calPath();
            ViewCompat.postInvalidateOnAnimation(JelloToggle.this);
        }
    }
};

计算出回弹的及具体值，然后刷新，并且这个值是回弹的

原文链接：http://www.apkbus.com/blog-880881-63442.html