使用“记住”来存储取消协程作业的函数

Question

如何记住 Jetpack Compose 中的函数？我希望

search

函数返回另一个函数，该函数将取消其两项作业，以便当用户再次点击

search

时，它不会启动另一个并行搜索，而是取消前一个：

这是

search

功能：

fun search(coroutineScope: CoroutineScope): () -> Unit {

        payments.clear()

        val channel = Channel<Payment>()

        val producer = coroutineScope.launch(Dispatchers.IO) {
            println("Query started.")
            fetchPayments(filter, channel)
            println("Query finished.")
        }
        val consumer = coroutineScope.launch {
            updatePayments(channel, payments)
            println("Updated: ${payments.size}")
        }
        return fun() {
            producer.cancel()
            consumer.cancel()
        }
    }

这个调用搜索，需要存储取消函数：

@Composable
fun Browser() {

    val coroutineScope = rememberCoroutineScope()
    val cancelSearch = remember {} // <-- What goes in here?

    Button(onClick = { 
            cancelSearch.value() // <-- this needs to cancel the previouis search (if any)
            cancelSearch = model.search(coroutineScope) // updates the cancellation function
        }, 
        modifier = Modifier.weight(1f)) {
            Text("Search")
        }
    )
}

Answer 1

这是一种保持函数处于状态的方法。

var cancelSearch by rememberSaveable { mutableStateOf<(() -> Unit)?>(null) }

Button(onClick = {
    cancelSearch?.invoke()
    cancelSearch = search(coroutineScope)
}