Use SavedStateHandle in view models

[Isira-Seneviratne]

Pass SavedStateHandle instead of Bundle to the view models. Values provided via an Intent's extras or a fragment's arguments are automatically passed to the state handle in the default view model factory implementation, which eliminates the need to implement a view model factory separately.

[dbrant]

Thanks -- this looks like it will be a worthwhile change. However, a change of this size requires a much better description.
The word "simplify" is not meaningful enough. There is a considerable reduction in code, but why is there a reduction in code?

Is it because SavedStateHandle automatically provides access to the Activity's intent extras and/or the Fragment's arguments? If so, this should be very clearly specified in your description. I'm not even seeing this described in Google's own documentation of SavedStateHandle, which worries me a bit. Can you point to where in the documentation does it endorse using SavedStateHandle in this way?

[Isira-Seneviratne]

Thanks -- this looks like it will be a worthwhile change. However, a change of this size requires a much better description. The word "simplify" is not meaningful enough. There is a considerable reduction in code, but why is there a reduction in code?

I updated the description to be more informative, hope that's better.

Is it because SavedStateHandle automatically provides access to the Activity's intent extras and/or the Fragment's arguments? If so, this should be very clearly specified in your description.

That's exactly what it does. The default view model factory automatically forwards data passed via the extras or arguments:

https://github.com/androidx/androidx/blob/androidx-main/activity/activity/src/main/java/androidx/activity/ComponentActivity.kt#L547
https://github.com/androidx/androidx/blob/976ab1f419ea26d4f7481267ffba338fb9b256ff/fragment/fragment/src/main/java/androidx/fragment/app/Fragment.java#L471

[machado001]

Minor comments =)

[machado001]

Just curious, what's the reason for this wildcard? I've seen it adopted in another file, TemplatesSearchViewModel, too.

[trietbui85]

This PR gets bigger and bigger. Should we separate it to multiple smaller PRs?