removeEventListener不删除firebase中的侦听器 [英] removeEventListener not removing listener in firebase

问题描述

我想在特定字段的值为true时从firebase ref中删除addValueEventListener侦听器。

I want to remove addValueEventListener listener from a firebase ref when value of particular field is true.

ValueEventListener valueListener=null;

private void removeListener(Firebase fb){
    if(valueListener!=null){
        **fb.removeEventListener(valueListener);**
    }
}

String key="https://boiling-heat-3083.firebaseio.com/baseNodeAttempt/" + userId+"/"+nodeType+"/"+nodeId+"/data";
final Firebase fb = new Firebase(key);
valueListener=fb.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot snap) {
        final HashMap<String, Object> data=(HashMap<String, Object>) snap.getValue();
        if( data.get("attemptFinish_"+nodeId)!=null){
            boolean title = (boolean) snap.child("attemptFinish_"+nodeId).getValue();
            if(title){
                removeListener(fb);
            }
        }
    }
    @Override
    public void onCancelled() {
        // TODO Auto-generated method stub
    }
});

但是没有删除addValueEventListener并且为firebase ref调用它。因此，如果需要，请建议我如何从任何firebase引用中删除侦听器。

But addValueEventListener is not getting removed and it's called for that firebase ref . So please suggest me how to remove listener from any firebase ref if required.

推荐答案

您可以从回调中删除侦听器：

You can remove the listener from within the callback with:

ref.removeEventListener(this);

所以一个完整的片段：

String key="https://boiling-heat-3083.firebaseio.com/baseNodeAttempt/" + userId+"/"+nodeType+"/"+nodeId+"/data";
final Firebase ref = new Firebase(key);
ref.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot snap) {
        if (snap.hasChild("attemptFinish_"+nodeId) {
            boolean isFinished = (boolean) snap.child("attemptFinish_"+nodeId).getValue();
            if(isFinished){
                ref.removeEventListener(this);
            }
        }
    }
    @Override
    public void onCancelled() {
        // TODO Auto-generated method stub
    }
});

我删除了 HashMap ，而不是使用方法 DataSnapshot 来实现同样的目标。我还将一些变量重命名为更清晰/更具惯用性。

I removed the HashMap, instead using the methods of the DataSnapshot to accomplish the same. I also renamed a few variables to be clearer/more idiomatic.

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