最近有看到一个问题,原文如下:
我用WindowManager.addView(view, params)方法添加了一个view,当我实现这个view的setOnTouchListener和setOnClickListener时,view只能监听ontouch事件,监听不到onclick事件,我去掉setOnTouchListener后就能监听到onclick事件,这是怎么回事?如何让这个view能监听到这2中事件?
发现有很多人对这个知识点有点模糊,回答之后,把自己的理解整理下,随便在这里分享一下。
下面是回答原文:
【0】这是因为回调函数的返回值所引起的。
onClick是不需要返回值的,而onTouch的返回值是boolean.
关于onTouch的返回值,官方解释如下:
*
This returns a boolean to indicate whether your listener consumes this event. The important thing is that this event can have multiple actions that follow each other. So, if you return false when the down action event is received, you indicate that you have not consumed the event and are also not interested in subsequent actions from this event. Thus, you will not be called for any other actions within the event, such as a finger gesture, or the eventual up action event.
*
如果在Touch事件的down action的时候返回false,则表示这个组件不会吃掉这个down event,并且对touch的后续动作都不感兴趣。那么整个touch的动作,从一开始刚点击下去的时候,你就不会再被回调到了。
官方还有一段注意的话:
Note: Android will call event handlers first and then the appropriate default handlers from the class definition second. As such, returning true from these event listeners will stop the propagation of the event to other event listeners and will also block the callback to the default event handler in the View. So be certain that you want to terminate the event when you return true.
如果某个Listener在回调到的时候返回了true,那么这个event就会被吃掉,而不能继续传播给其他的Listener。
【1】所以说如果在onTouch里面是返回true,那么onClick当然就无法再被回调了。
【2】可以用下面的代码测试下:
Button button = (Button)this.findViewById(R.id.button1);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v)
{
// TODO Auto-generated method stub
Log.d("Test","This is OnClick");
}
});
button.setOnTouchListener(new View.OnTouchListener() {
public boolean onTouch(View v, MotionEvent event)
{
// TODO Auto-generated method stub
Log.d("Test","This is onTouch,return false");
return false;