拦截点击/触摸事件而不覆盖 ViewGroup 或 View 方法

Question

有什么方法可以在不扩展View 或包装一些ViewGroup（可以拦截子事件）的情况下拦截/装饰视图的触摸事件？

假设我有处理项目点击事件的ExpandableListView。如果我在适配器返回的膨胀项视图上设置适配器OnClickListener 或OnTouchListener，ExpandableListView 不会执行相应的操作（组扩展），因为事件已被项的侦听器消耗。

我不想使用ExpandableListView#setOnItemClickListener 的原因是，我想在不使用ExpandableListView 依赖的情况下装饰适配器中的点击事件。

Answer 1

我找到了解决此问题的有效解决方案。

解决方案：在OnTouchListener 中收集事件克隆，然后将它们分派到父视图。

private final Queue<MotionEntry> consumedEvents = new LinkedList<>();
private final AtomicBoolean isDispatching = new AtomicBoolean(false);
...
    groupView.setOnTouchListener(new OnTouchListener() {
        @Override 
        public boolean onTouch(View v, MotionEvent e) {
            // we don't want to handle re-dispatched event...
            if (isDispatching.get()) {
                return false; 
            }
            // create clone as event might be changed by parent
            MotionEvent clone = MotionEvent.obtain(e);
            MotionEntry entry = new MotionEntry(v, clone);
            consumedEvents.add(entry);

            // consume ACTION_DOWN in order to receive subsequent motion events 
            // like ACTION_MOVE, ACTION_CANCEL/ACTION_UP...
            if (event.getActionMasked() == MotionEvent.ACTION_DOWN) {
                return true;
            }
            // we do not want to handle canceled motion...
            if (event.getActionMasked() == MotionEvent.ACTION_CANCEL) {
                consumedEvents.clear();
                return false;
            }
            // at this moment we have intercepted whole motion 
            // = re-dispatch to parent in order to apply default handling...
            if (event.getActionMasked() == MotionEvent.ACTION_UP) {
                dispatchEvents();
            }
            return true;
        }
    });
...

派送方式：

private void dispatchEvents() {
    isDispatching.set(true);
    while (!consumedEvents.isEmpty()) {
        MotionEntry entry = consumedEvents.poll();

        ViewGroup parent = (ViewGroup) entry.view.getParent();
        if (parent == null || entry.view.getVisibility() != View.VISIBLE) {
            continue; // skip dispatching to detached/invisible view
        }
        // make position relative to parent...
        entry.event.offsetLocation(entry.view.getLeft(), entry.view.getTop());
        entry.event.setSource(PARENT_DISPATCHER);
        parent.dispatchTouchEvent(entry.event);

        if (event.getActionMasked() == MotionEvent.ACTION_UP) {
            clickListener.onClick(entry.view);
        }
    }
    isDispatching.set(false);
}

助手类

private class MotionEntry {
    private final View view;
    private final MotionEvent event;

    public MotionEntry(View view, MotionEvent event) {
        this.view = view;
        this.event = event;
    }
}