SavedStateRegistryOwner should describe the implementing classes' responsibilities [228887344]

Fixed

Bug

Status Update

No update yet.

Description

il...@google.com

created issue #1

Apr 11, 2022 10:47PM

Component used: SavedState

Version used: 1.2.0-alpha02

The docs on SavedStateRegistryOwner do not explain the responsibilities and contract that the owner has on how they should implement SavedStateRegistryOwner or when they should call the methods on SavedStateRegistryController.

Ideally the class docs should talk through:

That performAttach() should be called only once, usually as part of the initialization of the owner. It must be called on the main thread.
That performRestore should be called unconditionally (either with null if no state is being restored or the Bundle of state to restore) either directly before moving the Lifecycle to CREATED or as part of a LifecycleObserver that is added as part of the initialization of the owner.
When the state of the owner is saved, performSave() must be called. The Bundle saved there should be what is later sent to performRestore().

Comments

il...@google.com <il...@google.com> Apr 14, 2022 04:58PM

Assigned to cl...@google.com.

cl...@google.com <cl...@google.com> Apr 14, 2022 04:59PM

Accepted by cl...@google.com.

ap...@google.com <ap...@google.com> #2Apr 19, 2022 10:44PM

Marked as fixed.

Are there many use cases for this? The current logic works fine with dark mode of platform, appcompat, and Compose.

le...@gmail.com <le...@gmail.com> #3Oct 21, 2022 02:20AM

When I was trying out integrating this with Now in Android, I ran into this issue since Now in Android currently doesn't inherit from AppCompatActivity and doesn't call AppCompatDelegate.setDefaultNightMode, so maybe the solution is instead to inherit from AppCompatActivity instead of just ComponentActivity to update the underlying configuration.

le...@gmail.com <le...@gmail.com> #4Oct 21, 2022 02:21AM

I just tested it with ComponentActivity. It's working fine for me. The scrim for 3-button nav and the icons are properly changed on light/dark mode switch. The extension function detect light/dark mode from resources.configuration.uiMode which is commonly used by the platform, AppCompat, and Compose, so I don't know why it doesn't work. Can I take a look at what you tried in Now in Android.

le...@gmail.com <le...@gmail.com> #5Oct 21, 2022 02:22AM

https://github.com/android/nowinandroid/tree/av/enable-edge-to-edge is the rough progress I made so far.

The theme switcher based on the user's preference within the app is handled separately from Configuration.uiMode and isn't updating the configuration directly, so I was attempting to call enableEdgeToEdge and manually specifying the dark and light themes.

The two options I see:

Allow a different way of specifying for enableEdgeToEdge whether the app is effectively in dark mode or light mode instead of that being based just on Configuration.uiMode (this issue)
Switch Now in Android to use AppCompatActivity and AppCompatDelegate.setDefaultNightMode so that the Configuration.uiMode is updated based on the user's preference

le...@gmail.com <le...@gmail.com> #6Oct 21, 2022 02:22AM

I see, so it has in-app light/dark setting.

On API 31+, apps with custom in-app light/dark settings should call UiModeManager.setApplicationNightMode to declare its theme to the system. This way, the system can use suitable colors duiring the splash screen. This should fix enableEdgeToEdge as well.

On API <31, it's easy if you can use AppCompatDelegate.setDefaultNightMode(int), but I can understand that you don't want to add appcompat dependency just for this.

So, custom mode is useful for apps that:

Provide in-app light/dark mode settings on API <31.
Don't want to depend on appcompat

I'm not sure if it's super common, but I guess the feature is worth implementing. I'll put it during the next alpha phase.

For Now in Android, I recommend you still call setApplicationNightMode on API 31+ regardless of enableEdgeToEdge. On API <31, just for the time being, you can either use the current e2e implementation, hide the setting, depend on appcompat, or just bear with the minor UI glitch. None of these are great, but I don't have a good solution now.