Move "preparation task" to a MainActivity before launching gui

Question

I have a running Android java written application and I would like to improve it.

For know my mainactivity, called DrugListActivty extend AppCompat. In short it's a recyclerView with Room database management.

I would like to move some part of the code in a MainActivity, in charge of checking database or onPause for example.

For now (and it's not working) I made :

public class MainActivity extends AppCompatActivity {
//some stuff
public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Intent intent = new Intent(this, DrugListActivity.class);
        startActivity(intent);

    }

And DrugListActivity became

public class DrugListActivity extends MainActivity {

//etc

I have blink effect, DrugListActivty is launch again and again and again.

Is my idea bad (move to simply code)? If is a good idea, there must be a right way to do it but I can't find any help.

So I'm asking the experts.

Thanks in advance for reading me, your advises and your time.