introducir el código aquí

private FirebaseAuth mAuth;
private EditText mEtxtEmail,mEtxtPassword;
private PresentadorLogin presentadorLogin;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Fabric.with(this, new Crashlytics());


    setContentView(R.layout.activity_main);

    FirebaseAuth mAuth = FirebaseAuth.getInstance();
    DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference();
     presentadorLogin = new PresentadorLogin(this,mAuth,mDatabase);
    mEtxtEmail = findViewById(R.id.etEmail);
  mEtxtPassword = findViewById(R.id.etPassword);
    Button mBtnLogin = findViewById(R.id.btnIngresar);
    mBtnLogin.setOnClickListener(this);


}


@Override
public void onClick(View v) {

    switch (v.getId()){
        case R.id.btnIngresar: String  email = mEtxtEmail.getText().toString().trim();
      String pass = mEtxtPassword.getText().toString().trim();
        presentadorLogin.signInUser(email,pass);
            break;
    }
}