java - 如何降低 android ScaleGestureDetector.SimpleOnScaleGestureListener 的灵敏度

Question

我有一个自定义的 SwipeRefreshLayout，里面有一个自定义的 GridView。我想根据捏/缩放手势更改该 GridView 的列号。我已经成功地实现了它。问题是，秤太敏感了。

例如，我有第 3-5 列。缩放到 3 或 5 很容易，但要缩放到 4 很难，因为缩放本身太敏感了。

这是我自定义的 SwipeRefreshLayout 类

/**
 * This class contains fix from http://stackoverflow.com/questions/23989910/horizontalscrollview-inside-swiperefreshlayout
 */
public class CustomSwipeRefreshLayout extends SwipeRefreshLayout {

    private int mTouchSlop;
    private float mPrevX;
    private ScaleGestureDetector mScaleGestureDetector;
    private ScaleListener mScaleListener;

    public CustomSwipeRefreshLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
    }

    public void setScaleListener(Context context, ScaleListener scaleListener) {
        this.mScaleListener = scaleListener;
        mScaleGestureDetector = new ScaleGestureDetector(context, new MyOnScaleGestureListener());
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent event) {
        if (mScaleGestureDetector != null) {
            mScaleGestureDetector.onTouchEvent(event);
        }

        switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_POINTER_DOWN:
                setEnabled(false);
                if (mScaleListener != null) {
                    mScaleListener.onTwoFingerStart();
                }
                break;
            case MotionEvent.ACTION_POINTER_UP:
                setEnabled(true);
                mPrevX = MotionEvent.obtain(event).getX();
                if (mScaleListener != null) {
                    mScaleListener.onTwoFingerEnd();
                }
                break;
            case MotionEvent.ACTION_DOWN:
                mPrevX = MotionEvent.obtain(event).getX();
                break;

            case MotionEvent.ACTION_MOVE:
                final float eventX = event.getX();
                float xDiff = Math.abs(eventX - mPrevX);

                if (xDiff > mTouchSlop) {
                    return false;
                }
        }

        return super.onInterceptTouchEvent(event);
    }

    class MyOnScaleGestureListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {

        private static final String TAG = "MyOnScaleGestureListene";

        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            if (mScaleListener != null) {
                // Too sensitive, must change to other approach
                float scaleFactor = detector.getScaleFactor();
                Log.d(TAG, "onScale: " + scaleFactor);
                if (scaleFactor > 1F) {
                    mScaleListener.onScaleUp(scaleFactor);
                } else if (scaleFactor < 1F) {
                    mScaleListener.onScaleDown(scaleFactor);
                } else {
                    // no scale
                }
            }
            return true;
        }

        @Override
        public boolean onScaleBegin(ScaleGestureDetector detector) {
            return true;
        }

        @Override
        public void onScaleEnd(ScaleGestureDetector detector) {
        }
    }

    public interface ScaleListener {
        void onTwoFingersStart();

        void onTwoFingersEnd();

        void onScaleUp(float scaleFactor);

        void onScaleDown(float scaleFactor);
    }
}

有什么办法可以降低ScaleGestureDetector.SimpleOnScaleGestureListener的灵敏度吗？如果没有办法，有没有办法解决？

这是一个显示问题的简短视频 https://www.youtube.com/watch?v=0MItDNZ_o4c

Answer 1

你应该有一个公差距离，这在Android世界中被称为“slop”。如果手势小于该容差，您应该忽略它。

private static final int SPAN_SLOP = 7;

...

@Override
public boolean onScale(@NonNull ScaleGestureDetector detector) {
    if (gestureTolerance(detector)) {
        // performing scaling
    }
    return true;
}

private boolean gestureTolerance(@NonNull ScaleGestureDetector detector) {
    final float spanDelta = Math.abs(detector.getCurrentSpan() - detector.getPreviousSpan());
    return spanDelta > SPAN_SLOP;
}

例如，您可以看到 @rallat 制作的展示开源应用程序.

在这里你可以找到source code和 presentation at GOTO Copenhagen 2016 .