使用地图调用 updateChildren（），Firebase获取每个键，并用该地图中的值替换该位置的对象。

关于 updateChildren（）的Firebase文档对此进行了说明：

给定一个像 alanisawesome 这样的单个键路径， updateChildren（）只会更新第一个子级别的数据，在第一个子级别之外传入的是一个setValue（）操作。

所以在你的情况下， /+ Constants.FIREBASE_LOCATION_USERS +/+ mEncodedEmail +/ subscribedTo的内容。

解决方法是在地图中使 PROG_ID 键的一部分：

pre $ userMap.put（/+ Constants.FIREBASE_LOCATION_USERS +/+ mEncodedEmail +/ subscribedTo /+ PROG_ID，true）;
firebaseRef.updateChildren（userMap，...


或者简单地调用

  firebaseRef.child（ /+ Constants.FIREBASE_LOCATION_USERS +/+ mEncodedEmail +/subscribedTo/\"+PROG_ID).setValue(true）; 
 

你会注意到，在这两种情况下，我摆脱了你的数组，赞成

 subscribedTo：{
 -KFPi5GjCcGrF-oaHnjr：true 
}，
 

I have a array called subscribedTo in my users node. Now I want to append some push ID's to that array whenever a user is subscribed.

But the push ID are being replaced instead of getting appended.

How can i append the push ID's to the array?

Schema

"tester@gmail,com": {
    "email": "tester@gmail,com",
    "hasLoggedInWithPassword": true,
    "name": "tester",
    "subscribedTo": [
      "-KFPi5GjCcGrF-oaHnjr"
    ],
    "timestampJoined": {
      "timestamp": 1459583857967
    }
  }

CODE

public void onSubscribe(View v) {

        final Firebase firebaseRef = new Firebase(Constants.FIREBASE_URL);

        final HashMap<String, Object> userMap = new HashMap<String, Object>();

        pushIDList.add(PROG_ID);
        userMap.put("/" + Constants.FIREBASE_LOCATION_USERS + "/" + mEncodedEmail + "/subscribedTo",
                pushIDList);

        firebaseRef.updateChildren(userMap, new Firebase.CompletionListener() {
            @Override
            public void onComplete(FirebaseError firebaseError, Firebase firebase) {
                Toast.makeText(ProgramDetail.this, "You are subscribed", Toast.LENGTH_SHORT).show();
            }
        });

    }

When you call updateChildren() with a map, Firebase takes each key and replaces the object at that location with the value from the map.

The Firebase documentation on updateChildren() says this about it:

Given a single key path like alanisawesome, updateChildren() only updates data at the first child level, and any data passed in beyond the first child level is a treated as a setValue() operation.

So in your case, you are replacing the entire contents of "/" + Constants.FIREBASE_LOCATION_USERS + "/" + mEncodedEmail + "/subscribedTo".

The solution is to either make the PROG_ID part of the key in the map:

userMap.put("/" + Constants.FIREBASE_LOCATION_USERS + "/" + mEncodedEmail + "/subscribedTo/"+PROG_ID, true);
firebaseRef.updateChildren(userMap, ...

Or to simply call setValue() at the lower location in the JSON tree:

firebaseRef.child("/" + Constants.FIREBASE_LOCATION_USERS + "/" + mEncodedEmail + "/subscribedTo/"+PROG_ID).setValue(true);

You'll note that in both cases I got rid of your array in favor of the recommended structure for such a so-called index:

"subscribedTo": {
  "-KFPi5GjCcGrF-oaHnjr": true
},