android - OnTouch 事件的行为如何？

Question

如果设备上有多个手指，onTouch-listener 是为每个手指运行一次，还是每个事件(手指按下、移动等)运行一次并包含每个 Activity 的触摸指针？

如果

(e.getAction() & MotionEvent.ACTION_MASK == MotionEvent.ACTION_MOVE)

我如何知道当前哪个指针正在移动？

final int pointerIndex = e.getActionIndex();
pointerID = e.getPointerId(pointerIndex);

出于某种原因总是返回 0(当 MotionEvent.ACTION_MOVE 时)..

Answer 1

首先，您获得这些事件:

1. MotionEvent.ACTION_DOWN
   第一次触摸屏幕
2. MotionEvent.ACTION_POINTER_DOWN
   对于所有非主要接触
3. MotionEvent.ACTION_UP
   最后一次修饰
4. MotionEvent.ACTION_POINTER_UP
   对于每一次非主要修饰
5. MotionEvent.ACTION_MOVE
   每当被触摸的手指移动
   这里你必须检查所有数字并检查坐标是否已更改

这样做:

@Override
public boolean onTouchEvent(MotionEvent ev)
{
    final int action = ev.getAction();
    final int pointerIndex = (action & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT; //index of this pointer

    switch (action & MotionEvent.ACTION_MASK)
    {
        case MotionEvent.ACTION_DOWN:
            //your first touch on the screen
            break;

        case MotionEvent.ACTION_MOVE:
            //one of the touches has moved
            for (unsigned int i = 0; i < ev.getPointerCount(); i++)
            {
                //The pointer id is ev.getPointerId(i);
                //for loop through all touches
            }
            break;

        case MotionEvent.ACTION_UP:
            //your last touch has gone up
            break;

        case MotionEvent.ACTION_POINTER_DOWN:
            //non-primary pointer has gone down
            break;

        case MotionEvent.ACTION_POINTER_UP:
            //non-primary pointer has gone up
            break;
        }
    }

    return true;
}

希望这对你有一点帮助:)