simple-stack-compose-1.kt

// 1. Setup simple-stack (lot of things has been omitted for brevity)
//    For a complete setup, https://github.com/Zhuinden/simple-stack-compose-integration/blob/master/README.md#what-does-it-do

class MainActivity : AppCompatActivity() {
  private val composeStateChanger = ComposeStateChanger()

  override fun onCreate(savedInstanceState: Bundle?) {
    ...
    val backstack = Navigator.configure()
      .setScopedServices(DefaultServiceProvider()) // <-- Support for scoped services
      .setStateChanger(AsyncStateChanger(composeStateChanger)) 
      .install(this, findViewById(R.id.container), History.of(FirstKey())) // <-- Initial destination is FirstKey, line: 31

    setContent {
      BackstackProvider(backstack) {
        composeStateChanger.RenderScreen() 
      }
    }
  }

  override final fun onBackPressed() {
    if (!Navigator.onBackPressed(this)) {
      super.onBackPressed()
    }
  }
}

// 2. Define destinations

@Immutable @Parcelize 
data class FirstKey(private val noArgsPlaceholder: String = ""): DefaultComposeKey(), DefaultServiceProvider.HasServices {
  override val saveableStateProviderKey: Any = this // <-- Important for `rememberSaveable`s
  override fun getScopeTag(): String = javaClass.name // <-- tag
  
  override fun bindServices(serviceBinder: ServiceBinder) {
    serviceBinder.add(FirstModel()) // <-- Registering service of class FirstModel
  }
  
  @Composable
  override fun ScreenComposable(modifier: Modifier) {
    val vm = rememberService<FirstModel>() // <-- Using the required service
    //.. content
  }
}


@Immutable @Parcelize 
data class SecondKey(private val name: String): DefaultComposeKey() {
  @Composable
  override fun ScreenComposable(modifier: Modifier) {
    // Retrieving the sample instance of FirstModel if the destination
    // exists in the backstack & is parent to the current.
    val vm = rememberService<FirstModel>(FirstKey.getScopeTag())
    //.. content
  }
}