Make AccessibilityInfo.setAccessibilityFocus cross platform

[draperunner]

Currently, AccessibilityInfo.setAccessibilityFocus is only available on iOS. The same behaviour can be achieved on Android by dispatching the proper accessibility event. I implemented the same function for Android, to make life slightly more convenient for the developer.

Today, developers must write something like this:

if (Platform.OS === 'ios') {
     AccessibilityInfo.setAccessibilityFocus(reactTag)
} else {
     UIManager.sendAccessibilityEvent(reactTag, 8)
}

With this change, the following is enough for both Android and iOS:

AccessibilityInfo.setAccessibilityFocus(reactTag)

Test Plan:

I made the same change in the react-native package in my project's node_modules, and checked that it worked on an Android device with TalkBack activated.

Release Notes:

[ANDROID] [ENHANCEMENT] [AccessibilityInfo] - Implement AccessibilityInfo.setAccessibilityFocus for Android

[mdvacca]

Thank you for this PR @draperunner.
I added a small comment.
Can you also update the documentation in: https://facebook.github.io/react-native/docs/accessibilityinfo#setaccessibilityfocus

Thank you!

[mdvacca]

Instead of set the value 8 here, you should export a new constant in UIManagerModuleConstants.AccessibilityEventTypes:

see:

react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/UIManagerModuleConstants.java

Line 138 in 26684cf

AccessibilityEvent.TYPE_VIEW_CLICKED));

and then use that new constant from here

[facebook-github-bot]

@mdvacca has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[mdvacca]

Great, thanks! I'm importing it.

[draperunner]

Awesome, thanks! Here is the documentation PR: facebook/react-native-website#461

[react-native-bot]

This pull request was closed by @draperunner in be715ec.

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