[iOS] - Display Alert correctly if app is using iOS13 Scenes API.

[hellostu]

Summary

UIApplication.keyWindow is deprecated. This is only a problem if an app is using the Scenes API. An app includes Scenes to display multiple windows and/or to enable the latest CarPlay. Using this API breaks Alerts. RCTAlertController uses UIApplication.keyWindow to display an alert. It does not display if using the Scenes API. This PR fixes this issue by doing a check for iOS13 and use of the Scenes API. It then grabs the foreground window. It falls back to the previous implementation in the else case.

Changelog

[iOS] [Fixed] - Display Alert correctly if app is using iOS13 Scenes API.

Test Plan

See React Native test app to demonstrate the fix below:
https://github.com/mixcloud/SceneApiAlertTest

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[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
ios	-	universal	n/a	--

Base commit: fc0b3fa

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	8,896,629	-23
android	hermes	armeabi-v7a	8,394,358	-29
android	hermes	x86	9,384,925	-21
android	hermes	x86_64	9,330,063	-23
android	jsc	arm64-v8a	10,348,457	+0
android	jsc	armeabi-v7a	9,829,278	+0
android	jsc	x86	10,398,251	+0
android	jsc	x86_64	10,983,646	+0

Base commit: fc0b3fa

[sammy-SC]

Hello @hellostu

could you please add photos that demonstrate the fix? Something that shows broken AlertController and then fixed.

Thank you.

[gaodeng]

anynews ?

[hellostu]

Hey @sammy-SC. Thanks for getting back to me and sorry for the late reply. If you are using the Scenes framework, then keyWindow doesn't work, which is react's mechanism for displaying an Alert. So this project demonstrates the fix:
https://github.com/mixcloud/SceneApiAlertTest

If you enable the Scenes framework on an existing project (as in the link above) then alerts simply don't display. This change would fix that by detecting the use of that framework and pointing to the correct UIWindow.

I'm not sure how best to demo it in an image?

[sammy-SC]

@hellostu I think a video would demo it best.

Something like:
Trying to present alert controller with Scenes framework enabled

• Include video before
• Include video after

Including code used to record the video is also helpful.

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