recomposing-livedata-observe.kt

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContent {
            val hello = remember { HelloModel(HelloResult.Pending) }

            Recompose { recompose ->
                observe(getHello()) {
                    onResult {
                        if (hello.state != result) {
                            hello.state = result
                        }
                    }
                }

                hello.state.let { state ->
                    when (state) {
                        is HelloResult.Pending -> Text("Loading...")
                        is HelloResult.Hello -> Text("Hello")
                        is HelloResult.Error -> {
                            Column {
                                Text("Error")
                                Button(onClick = {
                                    doError = false
                                    recompose()
                                }) {
                                    Text("Retry")
                                }
                            }
                        }
                    }
                }
            }
        }
    }

    var doError = true
    fun getHello(): LiveData<HelloResult> {
        if (doError) {
            return MutableLiveData(HelloResult.Error)
        } else {
            return MutableLiveData(HelloResult.Hello)
        }
    }

    sealed class HelloResult {
        object Pending : HelloResult()
        object Hello : HelloResult()
        object Error : HelloResult()
    }

    @Model
    data class HelloModel(
        var state: HelloResult = HelloResult.Pending
    )
}