CODEWITHSUNDEEP
javaandroidfirebasefirebase-realtime-database
Vishal Yadav
Vishal Yadav

Reputation: 1024

Get Last (5 or 10) value from Firebase

I am new in Android and I want to get last 5 or 10 messages from FirebaseDatabase.I've tried by using this.

ChatInteractor.databaseReference.orderByKey().startAt(10).endAt(20).addListenerForSingleValueEvent((ValueEventListener) ActivityChatView.this);

java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.firebase.database.Query com.google.firebase.database.DatabaseReference.orderByKey()' on a null object reference

enter image description here

   DatabaseReference databaseReference= FirebaseDatabase.getInstance().getReferenceFromUrl("https://afdbjkaffirebaseio.com/");
        Query query=databaseReference.child(Constants.ARG_CHAT_ROOMS).orderByChild("tKyhXXAf6TQnQgKyAf23RJcwhsn1_S5ClzMeWUEXR9evLJO9CBd9ABCH3").limitToLast(2);
        query.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {

                for(DataSnapshot snapshot:dataSnapshot.getChildren()){
                    Chat chat=snapshot.getValue(Chat.class);
                    Log.e("163","ACV"+chat.fromEmail);
                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });

 E/163: ACVnull

Upvotes: 1

Views: 4738

Answers (3)

Yashaswi N P
Yashaswi N P

Reputation: 933

DatabaseReference messagesReference = FirebaseDatabase.getInstance().getReference().child("chat_rooms").child("tKyhXXAf6TQnQgKyAf23RJcwhsn1_S5ClzMeWUEXR9evLJO9CBd9ABCH3");  
 Query chatQuery = messagesReference.orderByChild("your key").limitToLast(5);
     chatQuery.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    if (dataSnapshot.getValue() != null) {
    //do what ever required 
    }

Hope this helps. Please try.

Upvotes: 4

user8583580
user8583580

Reputation:

Update your code as shown below:

 DatabaseReference databaseReference= FirebaseDatabase.getInstance().getReference();
    Query query=databaseReference.child(Constants.ARG_CHAT_ROOMS).child("tKyhXXAf6TQnQgKyAf23RJcwhsn1_S5ClzMeWUEXR9evLJO9CBd9ABCH3").orderByChild().limitToLast("Number of last messages you want to show");
    query.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {

            for(DataSnapshot snapshot:dataSnapshot.getChildren()){
                Chat chat=snapshot.getValue(Chat.class);
                Log.e("163","ACV"+chat.fromEmail);
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

Upvotes: 4

Uttam Meerwal
Uttam Meerwal

Reputation: 324

i think u should use Query for this and that could be 

    @Override
public Query getQuery(DatabaseReference databaseReference) {
    // [START recent_posts_query]
    // Last 1000 posts, these are automatically the 1000 most recent
    // due to sorting by push() keys
    Query recentPostsQuery = databaseReference.child("posts")
            .limitToLast(number of post you want);
    // [END recent_posts_query]

    return recentPostsQuery;
}

this will give you post limited by number you given. you can get more info from Firebase official docs or their github repo Firebase link of github of fragment repo

hope this will help.......

Upvotes: 0

Related Questions