Currently, the final field mMainComponentName is used. This field is
initialized in the constructor of ReactActivityDelegate, and the
ReactActivityDelegate itself is initialized in the constructor of
ReactActivity. This means that the only way you can pass a main
component name to ReactActivityDelegate, is when your ReactActivity
subclass is constructed. At this point in the lifecycle of an
activity, the getIntent() value that the activity was initialized by
returns null, making it impossible to set the mainComponentName
dynamically based on data passed to the activity via an intent.

The mMainComponentName final field is also only used in onCreate of
the delegate, so it's not actually needed by the ReactActivityDelegate
at construction time. So the above limitation is not fundamental, it's
just a side effect of the API design.

By allowing subclasses of ReactActivityDelegate to implement a
getMainComponentName method, the subclass then has full control of how
to initialize the value. So an implementation of getMainComponentName
could be:

public String getMainComponentName() {
    return getIntent().getStringExtra("reactMainComponentName");
}

This commit doesn't remove anything and only adds a new method, so it
should be fully backwards compatible.

Thank you for sending the PR! We appreciate you spending the time to work on these changes.
Help us understand your motivation by explaining why you decided to make this change.

Test Plan

Related PRs

Release Notes

[ANDROID] [ENHANCEMENT] [ReactActivityDelegate] - Added ability for subclasses to override component name

Changelog:

[Android] [Enhancement] - Added ability for subclasses of ReactActivityDelegate to override component name