Google Cloud Messaging demo

Interaction layer

• GCMService - converts GCM platform-specific API to platform-indepndent Flow API In this variant the API exposed as static methods for sake of simplicity:

  • val tokenFlow: StateFlow
  • val messageFlow: SharedFlow
  • fun requestNewToken(): Unit

Use cases layer

ViewModels hide from UI Layer the interaction/business logic layer

• MessagesViewModel - Flow emits the list of all data notification messages received from last launch
• TokenViewModel - Flow emits the GCM tokens as soon as they are received either new or updated from the GC backend

UI Layer

• MainScreen - Composable to be put into scaffold and contains a column of (at least) 2 nested composables:

  • TokenView
  • MessagesView
  • SendView - commented out in the moment of writing this doc - development helper to bypass GC backend and send fake messages

• PushNotificationPermitted - a wrapper component ensures the permission are implicitly requested using Jetpack Compose Permissions API