多点触摸

https://blog.csdn.net/lijinweii/article/details/77717540

GestureDetector        ScaleGestureDetector

@Override
    public boolean onTouch(View v, MotionEvent event) {

        if (mGestureDetector.onTouchEvent(event))
            return true;
        mScaleGestureDetector.onTouchEvent(event);

        float x = 0, y = 0;
        // 拿到触摸点的个数
        final int pointerCount = event.getPointerCount();
        // 得到多个触摸点的x与y均值
        for (int i = 0; i < pointerCount; i++) {
            x += event.getX(i);
            y += event.getY(i);
        }
        x = x / pointerCount;
        y = y / pointerCount;

        /**
         * 每当触摸点发生变化时，重置mLasX , mLastY
         */
        if (pointerCount != lastPointerCount) {
            isCanDrag = false;
            mLastX = x;
            mLastY = y;
        }

        lastPointerCount = pointerCount;
        RectF rectF = getMatrixRectF();

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                if (rectF.width() > getWidth() || rectF.height() > getHeight()) {
                    getParent().requestDisallowInterceptTouchEvent(true);
                }
                break;
            case MotionEvent.ACTION_MOVE:
                if (rectF.width() > getWidth() || rectF.height() > getHeight()) {
                    getParent().requestDisallowInterceptTouchEvent(true);
                }
                Log.e(TAG, "ACTION_MOVE");
                float dx = x - mLastX;
                float dy = y - mLastY;

                if (!isCanDrag) {
                    isCanDrag = isCanDrag(dx, dy);
                }
                if (isCanDrag) {

                    if (getDrawable() != null) {
                        // if (getMatrixRectF().left == 0 && dx > 0)
                        // {
                        // getParent().requestDisallowInterceptTouchEvent(false);
                        // }
                        //
                        // if (getMatrixRectF().right == getWidth() && dx < 0)
                        // {
                        // getParent().requestDisallowInterceptTouchEvent(false);
                        // }
                        isCheckLeftAndRight = isCheckTopAndBottom = true;
                        // 如果宽度小于屏幕宽度，则禁止左右移动
                        if (rectF.width() < getWidth()) {
                            dx = 0;
                            isCheckLeftAndRight = false;
                        }
                        // 如果高度小雨屏幕高度，则禁止上下移动
                        if (rectF.height() < getHeight()) {
                            dy = 0;
                            isCheckTopAndBottom = false;
                        }

                        //设置偏移量
                        mScaleMatrix.postTranslate(dx, dy);
                        //再次校验
                        checkMatrixBounds();
                        setImageMatrix(mScaleMatrix);
                    }
                }
                mLastX = x;
                mLastY = y;
                break;

            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_CANCEL:
                Log.e(TAG, "ACTION_UP");
                lastPointerCount = 0;
                break;
        }
        return true;
    }