我想从片段中隐藏片段容器视图（在 MainActivity 布局内），但是当我单击任务按钮然后重新打开应用程序时它不起作用

Question

@Override
public void onResume() {
    super.onResume();

    Activity mainActivity = getActivity();
    mFragmentViewContainer_MainActivity =  mainActivity.findViewById(R.id.nav_host_fragment_containerView);
    mFragmentViewContainer_MainActivity.setVisibility(View.GONE);
}

it works when i open app first time but when i click on task button of android and then reopen app fragment container view became visible again even

i set visibility GONE inside OnResume

Answer 1

And don't really know if this work but try this !

In your fragment:

public class MyFragment extends Fragment {

    private MyFragmentListener mCallback;

    public interface MyFragmentListener{
        public actionFromParent(int visibility);
    }
    
    @Override
    public void onAttach(@NotNull Context context) {
        super.onAttach(context);
        mCallback = (MainActivity) context;
    }
    
    @Override
    public void onResume() {
        super.onResume();
        mCallback.actionFromParent(View.INVISIBLE);
    }

}

And your MainActivity:

public class MainActivity extends AppCompatActivity implements MyFragment.MyFragmentListener {

    private View view;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // ...
        
        view = findViewById(R.id.nav_host_fragment_containerView);
        
        // ...
    }
    
    @Override
    public void actionFromParent(int visibility){
        view.setVisibility(visibility);
    }

}

I don't know if this is a good think to use set visibility from onResume. Better to use it with a button except if you know what are you doing.