Android OnTouch向上/向下滑动方向更改 [英] Android OnTouch swipe up/down direction change

问题描述

我试图检测用户仍在屏幕上滑动时何时改变了滑动方向.

I'm trying to detect when an swipe direction was changed while the user still swipes on the screen.

我有类似以下内容(非常基本)来检测滑动方向:

I have something like this (very basic) for detecting the swipe direction:

@Override
public boolean onTouch(View view, MotionEvent motionEvent) {
    int action = motionEvent.getActionMasked();

    switch (action) {
        case MotionEvent.ACTION_DOWN: {
            Log.d(TAG, "onTouch: DOWN _Y = " + motionEvent.getRawY());
            mLastTouchY = mPrevTouchY = motionEvent.getRawY();

            break;
        }
        case MotionEvent.ACTION_MOVE: {
            Log.d(TAG, "onTouch: MOVE _Y = " + motionEvent.getRawY());

            final float dy = motionEvent.getRawY();
            if (dy >= mLastTouchY) {
                /* Move down */

            } else {
                /* Move up */

            }

            break;
        }
        case MotionEvent.ACTION_CANCEL:
        case MotionEvent.ACTION_OUTSIDE:
        case MotionEvent.ACTION_UP: {
            Log.d(TAG, "onTouch: UP _Y = " + motionEvent.getRawY());

            // snap page

            break;
        }
    }

    return true;
}

我需要的是实际检测用户何时更改了滑动方向. 例如，上面的代码无法检测到某些边缘情况:

What I need is to actually detect when the user changed the direction of the swipe. For example, the code above fails to detect some edge cases:

1. 从Y = 100开始，
2. 向下移动到150，
3. 前进到50，
4. 再次下移直到90

这将被检测为向上滑动，因为初始Y高于最后一个Y

推荐答案

是否要检测滑动的方向变化，有一种简单的方法:

Should you want to detect the direction change of the swipe there is a simple way:

    private GestureDetector gestureDetector;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        findViewById(R.id.myView).setOnTouchListener(this);
        gestureDetector = new GestureDetector(this, this);
    }

您可以像这样实现OnTouch和GestureListener:

And you implement OnTouch and GestureListeners like this:

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        return gestureDetector.onTouchEvent(event);
    }

    @Override
    public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
        if (distanceY > 0){
            // you are going up
        } else {
            // you are going down
        }
        return true;
    }

    @Override
    public boolean onDown(MotionEvent e) {
        return true;
    }
    //the rest of the methods you must implement...

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