Uncontrollable observable with commit()

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private final Disposable disposable = Observable.timer(5, TimeUnit.SECONDS)
            .subscribe(o ->
                    new MyDialogFragment()
                            .show(getSupportFragmentManager(), "DIALOG_TAG")
            );

    @Override
    protected void onPause() {
        super.onPause();
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
    }

    @Override
    protected void onStop() {
        super.onStop();
        disposable.dispose();
    }

}