java - Android MultiTouch 仅适用于一根手指

Question

我正在开发一款两人乒乓球游戏，希望用一根手指控制每只球棒。然而，我的问题是它一次只响应一根手指在屏幕上。整个游戏在一个 View 中运行。首先，我检查指针是否处于“Activity ”状态，然后检查它是否出现在屏幕的顶部或底部，然后再移动相应的 bat 。除了只有一次触摸记录外，它工作正常。我的方法代码如下:

    // variables
    int _touchY = (int) event.getY();
    boolean isTopSide = true;

    // test if motionEvent was on the top or bottom of the screen
    if (SCREEN_HEIGHT / 2 - _touchY < 0) {
        isTopSide = false;
    }

    switch (event.getActionMasked()) {

        case MotionEvent.ACTION_DOWN:
            _activePointer = event.getPointerId(0);
            break;

        case MotionEvent.ACTION_MOVE:
            if(_activePointer != INVALID_POINTER_ID) {
                if (isTopSide) { // top bat
                    _topBat.moveBat(event);
                } else { // bottom bat
                    _botBat.moveBat(event);
                }
            }
            if(_newPointer != INVALID_POINTER_ID){
                if (isTopSide) { // top bat
                    _topBat.moveBat(event);
                } else { // bottom bat
                    _botBat.moveBat(event);
                }
            }
            break;

        case MotionEvent.ACTION_UP:
            if(_activePointer != INVALID_POINTER_ID){
                _activePointer = INVALID_POINTER_ID;
            }
            break;

        case MotionEvent.ACTION_CANCEL:
            _activePointer = INVALID_POINTER_ID;
            break;

        case MotionEvent.ACTION_POINTER_UP:
            int pointerIndex = event.getActionIndex();
            int pointerId = event.getPointerId(pointerIndex);
            if(pointerId == _activePointer){
                _activePointer = INVALID_POINTER_ID;
            }

        case MotionEvent.ACTION_POINTER_DOWN:
            int newPointerIndex = event.getActionIndex();
            _newPointer = event.getPointerId(newPointerIndex);
            break;
    }

相关全局代码

// touched
private static final int INVALID_POINTER_ID = -1;
private int _activePointer = INVALID_POINTER_ID;
private int _newPointer = INVALID_POINTER_ID;

Answer 1

为什么您只看到单个指针的值的主要问题是因为没有任何参数的 event.getY() 为您提供了第一个指针索引的位置，即使该指针实际上移动的是第二个指针。

MotionEvent 类包含所有 Activity 指针的坐标。

如果您想获取第二个指针的位置，您需要调用event.getY(1)。

您可能希望循环遍历所有 Activity 点，通过 event.getPointerCount() 获取总计数，然后相应地发送事件。