java - 拦截点击/触摸事件而不重写 ViewGroup 或 View 方法

Question

有什么办法可以拦截/装饰 View 的触摸事件而不扩展View或包装在一些ViewGroup(它可以拦截子事件)中？

假设我有 ExpandableListView 来处理项目点击事件。如果我在适配器 OnClickListener 或 OnTouchListener 中设置适配器返回的膨胀项目 View ，则 ExpandableListView 不会执行相应的操作(组展开)，因为事件是由项目的监听器消耗。

我不想使用 ExpandableListView#setOnItemClickListener 的原因是，我想在适配器中装饰点击事件而不使用 ExpandableListView 依赖项。

Answer 1

我找到了解决这个问题的有效方法。

解决方案:在OnTouchListener中收集事件克隆，然后将它们分派(dispatch)到父 View 。

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;
        }
    });
...

发货方式:

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);
}

辅助类

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

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