Android Studio - Autenticacion Con Firebase 1/3

MainActivity.class

  private static final String TAG = "Antut" ;
    private FirebaseAuth mAuth;
    private FirebaseAuth.AuthStateListener mAuthListener;
    private EditText mEmailField,mPasswordField;
    private Button mLoginBtn;

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

        mAuth = FirebaseAuth.getInstance();

        mEmailField = (EditText) findViewById(R.id.email);
        mPasswordField = (EditText) findViewById(R.id.password);
        mLoginBtn = (Button) findViewById(R.id.login);

        mAuthListener = new FirebaseAuth.AuthStateListener() {
            @Override
            public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {

                if(firebaseAuth.getCurrentUser()!=null){

                    startActivity(new Intent(MainActivity.this,SegundaActivity.class));
                   
                }
                else {
                   // Toast.makeText(MainActivity.this, "Datos Incorrectos", Toast.LENGTH_SHORT).show();

                }
            }
        };

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




    }

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



    private void LoginUsuario(){


       String email = mEmailField.getText().toString();
        String password = mPasswordField.getText().toString();

        mAuth.signInWithEmailAndPassword(email, password)
                .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        Log.d(TAG, "signInWithEmail:onComplete:" + task.isSuccessful());

                        // If sign in fails, display a message to the user. If sign in succeeds
                        // the auth state listener will be notified and logic to handle the
                        // signed in user can be handled in the listener.
                        if (!task.isSuccessful()) {
                            Log.w(TAG, "signInWithEmail", task.getException());
                            Toast.makeText(MainActivity.this, "Authentication failed.",
                                    Toast.LENGTH_SHORT).show();
                        }

                        // ...
                    }
                });
             }




}