如何在android中实现“两指轻扫”手势？

public class MainActivity extends AppCompatActivity {
    private float startX, startY, endX, endY;
    private static final int MIN_DISTANCE = 150;

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        int action = event.getActionMasked();
        int pointerCount = event.getPointerCount();

        switch (action) {
            case MotionEvent.ACTION_DOWN:
                startX = event.getX();
                startY = event.getY();
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
                if (pointerCount == 2) {
                    startX = event.getX(0);
                    startY = event.getY(0);
                }
                break;
            case MotionEvent.ACTION_MOVE:
                if (pointerCount == 2) {
                    endX = event.getX(0);
                    endY = event.getY(0);

                    float deltaX = endX - startX;
                    float deltaY = endY - startY;

                    if (Math.abs(deltaX) > MIN_DISTANCE) {
                        if (deltaX > 0) {
                            // 向右滑动
                            // 执行相应操作
                        } else {
                            // 向左滑动
                            // 执行相应操作
                        }
                    } else if (Math.abs(deltaY) > MIN_DISTANCE) {
                        if (deltaY > 0) {
                            // 向下滑动
                            // 执行相应操作
                        } else {
                            // 向上滑动
                            // 执行相应操作
                        }
                    }
                }
                break;
        }

        return super.onTouchEvent(event);
    }
}