public abstract class ParentActivity extends AppCompatActivity {

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(getContentView());
        findViewById(R.id.button_parent).setOnClickListener(view -> Toast.makeText(this, "Parent onClick", Toast.LENGTH_LONG).show());
    }

    public abstract int getContentView();
}

public class MainActivity extends ParentActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        findViewById(R.id.button_child).setOnClickListener(view -> Toast.makeText(this, "Child onClick", Toast.LENGTH_LONG).show());
    }

    @Override
    public int getContentView() {
        return R.layout.activity_main;
    }
}