在Firebase群组消息传递应用中实施已读回执功能

Question

I'd like to implement a 'Seen' feature in my Firebase group messaging app. Can you kindly advise the best and most efficient approach to take (working code will be appreciated)? For example, the app would show " Seen by 6 " or " Seen by 15 " on a group message.

Here's my project: https://github.com/firebase/friendlychat/tree/master/android

Here's the MainActivity: https://github.com/firebase/friendlychat/blob/master/android/app/src/main/java/com/google/firebase/codelab/friendlychat/MainActivity.java

Answer 1

To achieve this, you need to add another node in your Firebase database named seenBy which must be nested under each messageId in meassage section. Your database should look like this:

Firebase-root
   |
   ---- messages
           |
           ---- messageId1
                   |
                   ---- meessage: "Hello!"
                   |
                   ---- timestamp: 1498472455940
                   |
                   ---- seenBy
                          |
                          ---- userUid1: John
                          |
                          ---- userUid2: Mary
                          |
                          ---- userUid3: George

Every time a new user opens a meesage, just add the uid and the name as explained above.

To implement Seen by 6 option, it's very easy. You just need to create a listener and use getChildrenCount() method like this:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference seenByRef = rootRef.child("messages").child(messageId).child("seenBy");
ValueEventListener eventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        long seenBy = dataSnapshot.getChildrenCount();
        Lod.d("TAG", "Seen by: " + seenBy);
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
};
seenByRef.addListenerForSingleValueEvent(eventListener);

To know whether a message has been opened or not, you need to add another field to your user section in which you need to add a boolean with the default value of false . This new section should look like this:

Firebase-root
   |
   ---- users
       |
       ---- userId1
           |
           ---- meessages
              |
              ---- messageId1: false
              |
              ---- messageId2: false
              |
              ---- messageId3: false

When a users opens that message, just set the value of that particular message from false to true , which means that the particular message has been opened. This is the code:

DatabaseReference openedRef = rootRef.child("users").child(userId).child("meessages").child("messageId1");
openedRef.setValue(true);

When you create a message, use push() method on the reference like this:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference messageRef = rootRef.child("meessages").push();
String messageKey = messageRef.getKey();

Having this key, you can use it in your DatabaseReference . In the same way you can use for the userId.

Hope it helps.

Answer 2

Yeah it is possible, You can add a child seen_by to the message, whenever user views the message append the viewers userId to the seen_by , then by retrieving the userID and you can count the number of viewers and also you can see the list of viewed members too. The format should be

message:{
    FirebaseKey:{
        message:"hi",
        timestamp:1498472455940,
        seen_by:"abc,def,ghi" //users UID
      }
    }