Android Firebase Database Error: Permission denied
<p>I am working on an android project that requires user email and pwd authentication. The details are stored in the firebase database.The problem occurs whenever I try logging in again with the email and password. In my logcat the error message is: </p>

<pre><code>W/SyncTree: Listen at / failed: DatabaseError: Permission denied
</code></pre>

<p>Take a look at my code below:</p>

<pre><code>public class LoginUser extends AppCompatActivity {

private RelativeLayout relativeLayout;

private EditText et_email, et_password;
private Button loginBtn;

private FirebaseAuth mAuth;
private FirebaseAuth.AuthStateListener authStateListener;
private DatabaseReference databaseReference;

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

    mAuth = FirebaseAuth.getInstance();
    databaseReference = FirebaseDatabase.getInstance().getReference();
    databaseReference.keepSynced(true);

    relativeLayout = (RelativeLayout) findViewById(R.id.activity_login_user);

    et_email = (EditText) findViewById(R.id.emailField);
    et_password = (EditText) findViewById(R.id.pwdField);
    loginBtn = (Button) findViewById(R.id.loginBtn);

    loginBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            initLogin();
        }
    });

    authStateListener = new FirebaseAuth.AuthStateListener() {
        @Override
        public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
            if (firebaseAuth.getCurrentUser() != null){
                initLogin();
            }
            else {
                startActivity(new Intent(LoginUser.this,RegisterFireBase.class));
            }
        }
    };

}

@Override
protected void onStart() {
    super.onStart();
    mAuth.addAuthStateListener(authStateListener);
}

@Override
protected void onStop() {
    super.onStop();
    if (mAuth != null){
        mAuth.removeAuthStateListener(authStateListener);
    }
}

private void initLogin() {

    String email = et_email.getText().toString().trim();
    String pass = et_password.getText().toString().trim();

    if (!TextUtils.isEmpty(email) &amp;&amp; !TextUtils.isEmpty(pass)){
        mAuth.signInWithEmailAndPassword(email,pass).addOnCompleteListener(this, new OnCompleteListener&lt;AuthResult&gt;() {
            @Override
            public void onComplete(@NonNull Task&lt;AuthResult&gt; task) {

                checkForUser();

            }
        });
    }
    else {
        Toast.makeText(this, "Some fields are empty", Toast.LENGTH_SHORT).show();
    }

}

private void checkForUser() {

    final String userId = mAuth.getCurrentUser().getUid();
    databaseReference.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            if (dataSnapshot.hasChild(userId)){

                Intent loginIntent =  new Intent(LoginUser.this, FireProfile.class);
                loginIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                startActivity(loginIntent);

                Snackbar.make(relativeLayout,"Log In Successful",Snackbar.LENGTH_LONG).show();

            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
}
</code></pre>

<p>}</p>

<p>What could be causing this?</p>