Unable to get All child data in Firebase Database using a Map?

问题

I am trying to display all child "name" located in my database tree. My Database tree I used the Map to do so:

GenericTypeIndicator<Map<String, Object>> m = new GenericTypeIndicator<Map<String, Object>>() {};
Map<String, Object> map = snapshot.getValue(m);
String username = (String) map.get("name");
displayName.setText(username);// Display the name

I am displaying all the data into a recyclerView. But for some reasons instead of getting all names(Eva, smith, princess), I am only one which is the lastest one created "princess" being displayed 3 times in my recyclerView layout(princess, princess, princess). Anyone has any idea what I am doing wrong?

回答1:

Assuming that you have a node named users in which you have all those uid's, to get all those name, please use the code below. Is the easiest way to achieve this.

DatabaseReference yourRef = FirebaseDatabase.getInstance().getReference().child("users");
ValueEventListener eventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        String userId = (String) dataSnapshot.getKey();

        DatabaseReference userIdRef = FirebaseDatabase.getInstance().getReference().child("users").child(userId);
        ValueEventListener eventListener = new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                 String name = (String) dataSnapshot.child("name").getValue();
                 Log.d("TAG", name);
            }

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

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

Hope it helps.

来源：https://stackoverflow.com/questions/44169044/unable-to-get-all-child-data-in-firebase-database-using-a-map