Firebase Android 排行榜系统

Question

I have the code:

listView = (ListView) findViewById(R.id.list);
    list = new ArrayList<String>();
    arrayAdapter = new ArrayAdapter(getApplicationContext(),  android.R.layout.simple_list_item_1,  list);

    leaderBoard();
}
FirebaseAuth auth = FirebaseAuth.getInstance();

public void leaderBoard(){
    database.getReference().child("db/auth/user/").addValueEventListener(new ValueEventListener() {
        public void onDataChange(DataSnapshot dataSnapshot) {
            if(dataSnapshot.exists()){
                list = new ArrayList<String>();
                for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                    System.out.println("The score is: " + snapshot.child("score").getValue());
                    String s = snapshot.child("name").getValue() + "         " + snapshot.child("score").getValue();
                    list.add(s);

                    arrayAdapter = new ArrayAdapter(getApplicationContext(), android.R.layout.simple_list_item_1, list);
                    listView.setAdapter(arrayAdapter);
                }
            }
        }


        @Override
        public void onCancelled(DatabaseError databaseError) {
            // Getting Post failed, log a message
            Log.w(TAG, "loadPost:onCancelled", databaseError.toException());

        }


    });

My goal is to show a list with the users' names and score, so far so good, as shown in the photo.

But now I need the list to show users and points in increasing order based on the score. Can someone help me?

image

Answer 1

To order the children by the value of their score property, you can do:

database.getReference().child("db/auth/user/").orderByChild("score").addValueEventListener(new ValueEventListener() {
  ...

As far as I can see, the rest of your code can remain the same.

Also see the Firebase documentation on ordering and filtering data .