如何在允许子视图处理点击的同时移动 ViewGroup？

Question

我有 FrameLayout 封装了两个 ImageViews。这是我想要的：

在用户触摸和拖动时移动整个布局，但当点击时，应由个人ImageViews（通过他们各自的View.OnClickListener()）处理

当前行为： 目前，当我尝试拖动视图组时，它会随机跳转一次（每个拖动事件），然后开始用手指移动。因此，就像您将手指移到视图组外，它也在移动。

其次，没有点击事件被路由到子ImageViews

我尝试过的：

我已尝试扩展封装ImageViews 的FrameLayout：

public class ChatHeadFrameLayout extends FrameLayout {

    /**
     * Store the initial touch down x coordinate
     */
    private float initialTouchX;
    /**
     * Store the initial touch down y coordinate
     */
    private float initialTouchY;

    public ChatHeadFrameLayout(@NonNull Context context) {
        super(context);
    }

    public ChatHeadFrameLayout(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    public ChatHeadFrameLayout(@NonNull Context context, @Nullable AttributeSet attrs, @AttrRes int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @RequiresApi(21)
    public ChatHeadFrameLayout(@NonNull Context context, @Nullable AttributeSet attrs, @AttrRes int defStyleAttr, @StyleRes int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent event) {
        // If the event is a move, the ViewGroup needs to handle it and return
        // the indication here
        switch (event.getAction()) {

            case MotionEvent.ACTION_DOWN:

                //remember the initial position
                initialTouchX = event.getRawX();
                initialTouchY = event.getRawY();
                return true;
        }
        return false;

    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        // Will be called in case we decide to intercept the event
        // Handle the view move-with-touch behavior here

        switch (event.getAction()) {

            case MotionEvent.ACTION_DOWN:

                //remember the initial position
                initialTouchX = event.getRawX();
                initialTouchY = event.getRawY();
                return true;

            case MotionEvent.ACTION_UP:
                int Xdiff = (int) (event.getRawX() - initialTouchX);
                int Ydiff = (int) (event.getRawY() - initialTouchY);


                //The check for Xdiff <10 && YDiff< 10 because sometime elements moves a little while clicking.
                //So that is click event.
                        if (Xdiff < 10 && Ydiff < 10) {
                            return false;
                        }
                return true;

            case MotionEvent.ACTION_MOVE:
                //Calculate the X and Y coordinates of the view.
                setX(event.getRawX() - initialTouchX);
                setY(event.getRawY() - initialTouchY);


                //Update the layout with new X & Y coordinate
                invalidate();

                return true;
        }
        return false;
    }
}

那么，这段代码有什么问题？

Answer 1

首先getRawX()的结果被翻译到屏幕0,0，getX()是相对于自己的view的。

另外，initialX 和 getCurrentX 的累积将只是拖动的值，您需要存储屏幕 x 并与拖动一起使用或计算 ACTION_MOVE 的每个差异并使用它

            //remember the initial position
            initialTouchX = event.getX();
            initialTouchY = event.getY();
            screenX = getX();
            screenY = getY();

然后 ON_MOVE

            setX(screenX + event.getX() - initialTouchX);
            setY(screenY + event.getY() - initialTouchY);

其次，您必须调用 super.onTouchEvent(MotionEvent.obtain(event)) 或 super.dispatchTouchEvent 作为 onTouchEvent 的第一行，因为您的视图正在消耗所有事件。

Answer 2

结果比我预期的要简单得多（请参阅下面评论中的解释）：

@Override
    public boolean onInterceptTouchEvent(MotionEvent event) {
        // The plan is to intercept the events here and if,
        // 1) The move is an ACTION_DOWN, return false indicating we want more events
        // to be able to ascertain if we want this ViewGroup to move or the children
        // views to handle the click event.
        // 2) On receiving the ACTION_MOVE, of course, move the ViewGroup but the sure short
        // indication of click would be to check it for in ACTION_DOWN with threshold of 5px.
        // In that case, we would return super.onInterceptTouchEvent(event); meaning, let the
        // event handling happen normally without interception
        // (Remember - the ACTION_DOWN had been recorded by the children previously when we
        // returned false and on receiving the ACTION_UP, it would constitute the complete event)
        switch (event.getAction()) {

            case MotionEvent.ACTION_DOWN:

                // remember the initial position
                initialTouchX = event.getX();
                //Log.d(TAG, "onInterceptTouchEvent().ACTION_DOWN.initialTouchX: " + initialTouchX);
                initialTouchY = event.getY();
                //Log.d(TAG, "onInterceptTouchEvent().ACTION_DOWN.initialTouchY: " + initialTouchY);
                return false;

            case MotionEvent.ACTION_UP:
                int xDiff = (int) (event.getX() - initialTouchX);
                int yDiff = (int) (event.getY() - initialTouchY);


                //The check for Xdiff <5 && YDiff< 5 because sometime elements moves a little while clicking.
                //So that is click event.
                if (xDiff < 5 && yDiff < 5) {
                    return super.onInterceptTouchEvent(event);
                }
                return false;

            case MotionEvent.ACTION_MOVE:

                int moveX = (int) (event.getX() - initialTouchX + getX());
                int moveY = (int) (event.getY() - initialTouchY + getY());

                setX(moveX);
                setY(moveY);

                //Update the layout with new X & Y coordinate
                invalidate();
        }
        return false;

    }

此解决方案有一个警告：点击事件仅基于移动的距离。通常，为了区分单击和长按，您还可以执行this 之类的操作：

private long lastTouchDown;
private static int CLICK_ACTION_THRESHHOLD = 200;

@Override
public boolean onTouch(View v, MotionEvent event) {
    switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            lastTouchDown = System.currentTimeMillis();
            break;
        case MotionEvent.ACTION_UP:
            if (System.currentTimeMillis() - lastTouchDown < CLICK_ACTION_THRESHHOLD) {
                Log.w("App", "You clicked!");
            }
            break;
    }
    return true;
}

P.S：在提出的解决方案中不需要覆盖onTouchEvent() 方法。