To get all user names, of all User objects that exist under "Users" node, please use the following lines of code:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference usersRef = rootRef.child("Users");
productsRef.get().addOnCompleteListener(new OnCompleteListener<DataSnapshot>() {
@Override
public void onComplete(@NonNull Task<DataSnapshot> task) {
if (task.isSuccessful()) {
for (DataSnapshot ds : task.getResult().getChildren()) {
String name = ds.child("name").getValue(String.class);
Log.d(TAG, name);
}
} else {
Log.d(TAG, task.getException().getMessage()); //Don't ignore potential errors!
}
}
});
Because there are several objects within the "Users" node, first you need to get a reference to that node, attach a listener and then loop through the results. The result in the logcat will be:
jm
...
If you want to use the Firebase-UI library, then simply pass the "usersRef" to the FirestoreRecyclerOptions's setQuery() method, as explained in my answer from the following post: