java - 根据速度或其他变量向左、向右、向上和向下滑动

Question

我有一个从简单手势扩展的类，我正在使用 onfling 方法:

class MyGestureListener extends GestureDetector.SimpleOnGestureListener{
    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
            float velocityY) {
        // TODO Auto-generated method stub
        float e1_X = e1.getX();
        float e1_Y = e1.getY();
        float e2_X = e1.getX();
        float e2_Y = e2.getY();
        if(velocityX > 0 && velocityX > velocityY){
            text.setText("Swipe left");
        }else if(velocityX < 0 && velocityX < velocityY){
            text.setText("Swipe right");
        }else if(velocityY < 0 && velocityX > velocityY){
            text.setText("Swipe down");
        }else if(velocityY > 0 && velocityX < velocityY){
            text.setText("Swipe up");
        }
        return super.onFling(e1, e2, velocityX, velocityY);
    }
}

我知道这取决于某些角度，但我做不到，我尝试使用 velocityX 和 velocityY，只有在精确操作时它才有效。但我想要的是一个“错误”的角度:如果你对角线滑动，例如向上和向右，我需要选择哪个是好的方式。

Answer 1

您应该检查速度和距离。这是水平滑动检测器的示例。您可以以相同的方式添加垂直检测。

public class HSwipeDetector extends SimpleOnGestureListener {
    private static final int SWIPE_MIN_DISTANCE = 120;
    private static final int SWIPE_MAX_OFF_PATH = 250;
    private static final int SWIPE_THRESHOLD_VELOCITY = 200;

    @Override
    public boolean onFling(final MotionEvent e1, final MotionEvent e2, final float velocityX, final float velocityY) {
        if (Math.abs(e1.getY() - e2.getY()) > SWIPE_MAX_OFF_PATH) {  return false;  }

        /* positive value means right to left direction */
        final float distance = e1.getX() - e2.getX();
        final boolean enoughSpeed = Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY;
        if(distance > SWIPE_MIN_DISTANCE && enoughSpeed) {
            // right to left swipe
            onSwipeLeft();
            return true;
        }  else if (distance < -SWIPE_MIN_DISTANCE && enoughSpeed) {
            // left to right swipe
            onSwipeRight();
            return true;
        } else {
            // oooou, it didn't qualify; do nothing
            return false;
        }
    }

    protected void onSwipeLeft() { 
        // do your stuff here
    }

    protected void onSwipeRight() {   
        // do your stuff here
    }
}