onCreate(null) ?

[bojanlozanovski77]

Hi, it seems like it'd become a standard for this onCreate(null) to be used as part of the main activity.

Given that this can be quite harmful for native apps that use RN only for a limited set of functionalities, what do you think about limiting the scope of what state is not preserved to only the RN related state not being preserved, and the state for the rest of the app to be preserved.

I've come up with something like this:

• Custom Fragment Factory that won't instantiate your RN fragment, and also the fragment from this specific RN library. In particular, instead of them it will instantiate a self closing fragment.
• setting this factory to the activity fragment manager...
• optionally, in activity on create, you can clear the back stack...

this way, the app state is preserved, while only the rn fragment state is not preserved.

custom factory:

private const val REACT_NATIVE_SCREENS_PACKAGE_PREFIX: String = "com.swmansion.rnscreens"

class CustomFragmentFactory : FragmentFactory() {

    override fun instantiate(classLoader: ClassLoader, className: String): Fragment {

        return if (className.startsWith(REACT_NATIVE_SCREENS_PACKAGE_PREFIX)
            || className == CustomRNSDKFragment::class.qualifiedName) {
            NoOpFragment();
        } else {
            super.instantiate(classLoader, className)
        }
    }
}

self closing fragment:

class NoOpFragment: Fragment() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        // Immediately remove the fragment when it's created
        parentFragmentManager.beginTransaction()
            .remove(this)
            .commitAllowingStateLoss()
    }

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? = null
}

in main activity (we set the factory before super.onCreate(...)):

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {

        getSupportFragmentManager().setFragmentFactory(new CustomFragmentFactory());

        super.onCreate(savedInstanceState);

...

additionally, this can also be added inside main activity oncreate:

            getSupportFragmentManager().popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
            
            // depending on the use case.

[kkafar]

This looks very promising! Thanks a lot. I'll have hard time this upcoming week to give it any deeper thought, however I'll return back to you once I do!

[bojanlozanovski77]

Thanks for the quick response. In the tests that I did up until now, the first impression is that this solved the issue for me. I’m looking forward to you and/or other people giving it a go/thought.

[Skalakid]

Hello @bojanlozanovski77, thank you for sharing this excellent solution. It’s a great improvement over the current workaround 🚀 We've been working recently on handling configuration changes in React Native and the screens package, and a custom fragment factory seems to work for all different cases! For sure, it's a more precise way to handle the problem, and it won't affect the native side of the brownfield applications. Because of that, we would love to add this solution to our library and adjust the installation steps with it. I will prepare the PR. Thank you once again 😄

[bojanlozanovski77]

Proszę bardzo! 😊 I'm glad I could be of some help. Thank you for adding me as a co-author to the PR.

[kkafar]

Thanks a lot for the idea @bojanlozanovski77 and @Skalakid for the implementation.

I'll land #3089 which should close the discussion.

[grahammendick]

Hi, just wanted to let you know the Navigation router handles this a different way that means you don't have to edit the MainActivity at all. Remove the throw from your empty constructor on your fragments because this is what's called when they're restored. Then if they've been instantiated via the empty constructor return a blank View from onCreateView.

override fun onCreateView(
  inflater: LayoutInflater,
  container: ViewGroup?,
  savedInstanceState: Bundle?,
): View {
  if (screen) {
    // normal processing
    return coordinatorLayout;
  }
  return View(requireContext());
}