Android 图片双击围绕中心点放大和MotionEvent分析

使用switch (event.getAction())可以处理ACTION_DOWN和ACTION_UP事件

使用switch (event.getAction() & MotionEvent.ACTION_MASK)就可以处理处理多点触摸的ACTION_POINTER_DOWN和ACTION_POINTER_UP事件

ACTION_DOWN和ACTION_UP就是单点触摸屏幕，按下去和放开的操作；
ACTION_POINTER_DOWN和ACTION_POINTER_UP就是多点触摸屏幕，当有一只手指按下去的时候，另一只手指按下和放开的动作捕捉；
ACTION_MOVE就是手指在屏幕上移动的操作

附上一图片类似布卡漫画图片放大的代码

@Override
	public boolean onTouchEvent(MotionEvent event)
	{
		int pointcount = event.getPointerCount();
		F.out("pointcount=" + pointcount);
		if (pointcount == 1)
		{
			if (!PlayerActivity.this.thisActivityGesture.onTouchEvent(event))
			{

			}
		}
		if (pointcount == 2)
		{
			switch (event.getAction() & MotionEvent.ACTION_MASK)
			{
			case MotionEvent.ACTION_POINTER_DOWN:
				oldDistance = (float) Math.sqrt((event.getX(0) - event.getX(1)) * (event.getX(0) - event.getX(1)) + (event.getY(0) - event.getY(1)) * (event.getY(0) - event.getY(1)));
				oldpiont.set((int) (event.getX(0) + event.getX(1)) / 2, (int) (event.getY(0) + event.getY(1)) / 2);
				F.out(" oldDistance=" + oldDistance);
				break;
			case MotionEvent.ACTION_MOVE:
				float newDistance;
				newDistance = (float) Math.sqrt((event.getX(0) - event.getX(1)) * (event.getX(0) - event.getX(1)) + (event.getY(0) - event.getY(1)) * (event.getY(0) - event.getY(1)));
				if (newDistance > 10f)
				{
					F.out("newDistance=" + newDistance + " oldDistance=" + oldDistance);
					if (imageView != null) imageView.scaleView(newDistance / oldDistance, oldpiont.x, oldpiont.y);
					oldDistance = newDistance;
				}
				break;
			case MotionEvent.ACTION_POINTER_UP:
				oldDistance = 10;
				oldpiont.set(0, 0);
				break;
			}
		}
		return false;
	}

类似布卡漫画的功能，图片围绕双击的中心变大，而且还可以托动

代码:http://download.youkuaiyun.com/detail/yanglian20009/4531486