CODEWITHSUNDEEP
androidfirebase-realtime-database
Leonardo Oneda
Leonardo Oneda

Reputation: 13

Retrieving data from Firebase database is returning null

My app is saving users in my firebase database, but when I try to read the value of the object it always returns null. The rules of my firebase are all set true and the app is saving the users properly. I don't know why I can't read the data and why it always returns null. This is my MainActivity class:

package com.example.leo_o.testfirebase;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

public class MainActivity extends AppCompatActivity implements 
View.OnClickListener {

private Button saveButton;
private EditText nameEditText;
private DatabaseReference mDatabase;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    mDatabase = FirebaseDatabase.getInstance().getReference("users");
    saveButton = (Button) findViewById(R.id.saveButton);
    nameEditText = (EditText) findViewById(R.id.nameEditText);
}

private void saveUser(String name) {
    User user = new User(name);
    String userId = mDatabase.push().getKey();
    mDatabase.child(userId).setValue(user);
}

public void getData() {
    ValueEventListener userListener = new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            User user = dataSnapshot.getValue(User.class);
            String name = user.getName();
            if (name == null) {
                Toast.makeText(MainActivity.this, "Null value", Toast.LENGTH_SHORT).show();
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {
        }
    };
    mDatabase.addValueEventListener(userListener);
}

@Override
public void onClick(View view) {
    if (view == saveButton) {
        String name = nameEditText.getText().toString();
        saveUser(name);
        getData();
    }
}

}

An this is my User class:

package com.example.leo_o.testfirebase;

public class User {

public String name;

public User() {
}

public User(String name) {
    this.name = name;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

}

Does anyone know what is wrong with my code and why it always returns null?

Upvotes: 1

Views: 646

Answers (1)

Amit Barjatya
Amit Barjatya

Reputation: 259

Your mDatabase points to the "users" node in firebase so the value that you are getting in "onDataChange" is a list of users and not a single user.

See how you are setting the value: mDatabase.child(userId).setValue()

You need to do the same if you just want to get the details of a single user. Attach the value event to a userId node.

Alternatively, you can also use a child event listener on mDatabase.

Upvotes: 1

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