Android Firebase：未调用方法“ onDataChange”

Question

来自FirebaseManager类

此方法连接到“ Firebase实时数据库”以检索数据并通过回调将其分配给主要活动

self.Numero_resoluciones = "";
self.ui.label_6.setText(self.Numero_resoluciones) # But I can´t see it here
print(self.Numero_resoluciones) #I can see the value`

“获取用户”方法返回带有dataSnapshot的回调。

  public void getUser(final DataSnapshotCallback callback){


    dbRef.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            System.out.println("dentro onDataChange");
            callback.onResult(dataSnapshot);
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
}