How to call Kotlin coroutine in composable function callbacks?

debugcn 投稿 Dev

Rawieo

I want to call a suspend-function inside of a callback of composable-function.

suspend fun getLocation(): Location? { /* ... */ }

@Composable
fun F() {

    val (location, setLocation) = remember { mutableStateOf<Location?>(null) }

    val getLocationOnClick: () -> Unit = {
        /* setLocation __MAGIC__ getLocation */
    }

    Button(onClick = getLocationOnClick) {
        Text("detectLocation")
    }

}

If I would have used Rx then I could just subscribe.

I could do invokeOnCompletion and then getCompleted, but that API is experimental.

I can't use launchInComposition in getLocationOnClick because launchInComposition is @Composable and getLocationOnClick can not be @Composable.

What would be the best way to get result of a suspending function inside a regular function, inside @Composable function?

2jan222

You can use the viewModelScope of a ViewModel or any other coroutine scope.

Example of Deleting Action for an Item from LazyColumnFor which requires a suspend call handled by a ViewModel.

     class ItemsViewModel : ViewModel() {

        private val _itemList = MutableLiveData<List<Any>>()
        val itemList: LiveData<List<Any>>
            get() = _itemList

        fun deleteItem(item: Any) {
            viewModelScope.launch(Dispatchers.IO) {
                TODO("Fill Coroutine Scope with your suspend call")       
            }
        }
    }

    @Composable
    fun Example() {
        val itemsVM: ItemsViewModel = viewModel()
        val list: State<List<Any>?> = itemsVM.itemList.observeAsState()
        list.value.let { it: List<Any>? ->
            if (it != null) {
                LazyColumnFor(items = it) { item: Any ->
                    ListItem(
                        item = item,
                        onDeleteSelf = {
                            itemsVM.deleteItem(item)
                        }
                    )
                }
            } // else EmptyDialog()
        }
    }

    @Composable
    private fun ListItem(item: Any, onDeleteSelf: () -> Unit) {
        Row {
            Text(item.toString())
            IconButton(
                onClick = onDeleteSelf,
                icon = { Icons.Filled.Delete }
            )
        }
    }

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