In App Message Manager
Registers the in-app message manager, which will listen to and display incoming in-app messages. The current Activity is required in order to properly inflate and display the in-app message view.Important note: Every Activity must call registerInAppMessageManager in the onResume lifecycle method, otherwise in-app messages may be lost! This method also calls ensureSubscribedToInAppMessageEvents. To be sure that no in-app messages are lost, you should call ensureSubscribedToInAppMessageEvents as early as possible in your app, preferably in your onCreate.
The current Activity.