Firebase DatabaseReference没有事件侦听器移除？

问题描述

嘿，我需要在某个时候删除这个监听器，还是它自己被删除？我有这个在我的活动中的一个片段调用，用户可以去另一个视图没有被销毁。因此，不知道如果我以某种方式假设要消除 onDestroy ， onPause 调用？我没有办法删除它，因为它是一个 DatabaseReference

这是代码：

  private DatabaseReference mDatabase; 
 mDatabase.child（projects）。orderByChild（viewCount）。limitToLast（15）.addChildEventListener（new ChildEventListener（）{
 @Override 
 public void onChildAdded（DataSnapshot dataSnapshot，String s）{
  

解决方案

您确实需要删除相反生命周期事件中的侦听器。

要删除侦听器，您需要保留：

$ p $ Query query = mDatabase.child （projects）。orderByChild（viewCount）。limitToLast（15）;
ChildEventListener listener = query.addChildEventListener（new ChildEventListener（）{...
pre>

然后：

$ p $ query.removeChildEventListener（收听）;


你可以看到我明确地使用了一个 Query 在这里，因为这是你真正的附加你的听众。但是如果你有一个简单的 DatabaseReference ，那么同样的方法是可用的，因为 DatabaseReference 从继承。

Hey do I need to remove this listener at some point, or does it get removed on its own? I have this called in a fragment within my activity, and users can go to another view without this one being destroyed. Therefore not sure if I am somehow suppose to remove this in an onDestroy, onPause call? I do not see a way to remove it since it is a DatabaseReference

Here is the code:

private DatabaseReference mDatabase;
  mDatabase.child("projects").orderByChild("viewCount").limitToLast(15).addChildEventListener(new ChildEventListener() {
            @Override
            public void onChildAdded(DataSnapshot dataSnapshot, String s) {

解决方案

As the answer superman links to show: you indeed will need to remove the listener in the opposite lifecycle event.

To remove a listener, you need to keep the handle that is returned when you call addChildListener():

Query query = mDatabase.child("projects").orderByChild("viewCount").limitToLast(15);
ChildEventListener listener = query.addChildEventListener(new ChildEventListener() { ...

And then pass it to removeEventListener():

query.removeChildEventListener(listener);

You can see that I explicitly use a Query here, since that is what you actually attach your listener to. But if you have a plain DatabaseReference the same methods are available, since DatabaseReference inherits from Query.

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