Android OnTouch 方法值无法初始化

Question

在我的应用程序中，我想计算两个距离之间的比率，但我不知道为什么变量 dist1 和 dist2 没有保存我在 IF ELSE 语句中计算的值，我的代码有什么问题？

任何指导或帮助将不胜感激。

这是方法编码:

@Override
public boolean onTouchEvent(MotionEvent event) {
    final int action = event.getAction() & MotionEvent.ACTION_MASK;
    float x, y, x1, x2, y1, y2, dist1, dist2;
    int pointerIndex;

    if(event.getPointerCount()==1){
        if (action == MotionEvent.ACTION_DOWN) {
            x = event.getX();
            y = event.getY();
        } else {
            pointerIndex = event.getActionIndex();
            x = event.getX(pointerIndex);
            y = event.getY(pointerIndex);
        }
        mRenderer.setXY(x, y);
        requestRender();
    }
    if(event.getPointerCount()==2){
        if (action == MotionEvent.ACTION_POINTER_UP) {
            x1 = event.getX(0);
            y1 = event.getY(0);
        }else {
            x1 = event.getX(0);
            y1 = event.getY(0);
        }
        if (action == MotionEvent.ACTION_POINTER_DOWN) {
            x2 = event.getX(1);
            y2 = event.getY(1);
            dist1 = (float)Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
            Log.v("DIST1: ", String.valueOf(dist1));
        } else {
            x2 = event.getX(1);
            y2 = event.getY(1);
            dist2 = (float)Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
            Log.v("DIST2: ", String.valueOf(dist2));
        }
        ratio = dist2/dist1;//here the dist2 and dist1 is not initialized
    }
    return true;
}

Answer 1

您正在尝试通过两个单独的触摸事件设置 dist1 和 dist2。您已在 onTouchEvent() 方法中声明了这两个变量。一旦此方法返回，变量就会超出范围并不再存在。

您需要做的是在某个地方声明它们，该位置将持续存在多个触摸事件。最简单的方法是将它们声明为周围类的成员。

private float dist1, dist2;

@Override
public boolean onTouchEvent(MotionEvent event) {
    float x, y, x1, x2, y1, y2; // Do not re-declare dist1 and dist2 here
    ...
}