override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    var mAuth = FirebaseAuth.getInstance().currentUser

    if(mAuth!=null){
        intent = Intent(this, EjemploActivity::class.java)
        startActivity(intent)
    }
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);
    FirebaseUser mAuth = FirebaseAuth.getInstance().getCurrentUser();
    if(mAuth!=null){
        startActivity(new Intent(getApplicationContext(),EjemploActivity.class));
    }
}