How to call all activity onDestroy() when MainAcitivty call onDestroy()?

Question

I made two activities for the test.

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        ...
        Button button = findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(MainActivity.this, SubActivity.class));
            }
    }

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

This button in MainActivity can start SubActivity.

public class SubActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        ...
    }

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

    @Override
    public void onBackPressed() {
        startActivity(new Intent(SubActivity.this, MainActivity.class));
    }
}

When in SubActivity, press back button, it doesn't call onDestroy() in SubActivity class and start MainActivity. What I want to do is, How to call SubActivity onDestroy() when I finish the MainActivity? It doesn't call SubActivity onDestroy() when I press the back button in MainActivity. Is there any solution like using Intent.FLAG_ACTIVITY?

Answer 1

You should finish() your SubActivity in onBackPressed to destroy it and go back to your MainActivity, instead of doing a startActivity. In many cases, that is the behavior you'll get even if you don't implement onBackPressed yourself. Your current code is starting a second MainActivity.