Can't add in Firebase when authentified Android

Question

I can't add a comment in firebase when I am authentified.

There is my rules.

{
    "rules": {
        ".read": true,
        ".write": "auth != null"
    }
}

My activity where I test if user is not null before push in firebase.

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        String baseUrl = "url";
        final Firebase fb = new Firebase(baseUrl+"/comments");
        final EditText et = (EditText) findViewById(R.id.comment);
        final FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
        Button btn = (Button) findViewById(R.id.send);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(user != null)
                    fb.push().child("comment").setValue(et.getText().toString());
            }
        });
    }

}

Error I get in log

W/RepoOperation: setValue at /comments/-L0shVMfCJWab7_5ltnO/comment failed: FirebaseError: Permission denied

When I change the rule of write to true, it work.

Answer 1

I resolve the problem, instead use Firebase Instance I use DatabaseReference.

Here is the code

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    String baseUrl = "https://tpdevproject.firebaseio.com/";
    final DatabaseReference fb = FirebaseDatabase.getInstance().getReference("comments");
    final EditText et = (EditText) findViewById(R.id.comment);
    final FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
    Button btn = (Button) findViewById(R.id.send);
    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if(user != null)
                    fb.push().child("comment").setValue(et.getText().toString());
            }
        });
    }

}

Answer 2

You need to specify both rules are true in firebase console-:

{
    "rules": {
        ".read": true,
        ".write": true,
    }
}

Answer 3

Try this:

{
    "rules": {
        ".read": true,
        ".write": "auth !== null"
    }
}

Note the !== in the write rule, with two equals signs instead of one.

This answer is based on some examples in the Firebase documentation on User Based Security .