How to refresh UI in Kotlin with Compose desktop when runBlocking? - kotlin

Question

I'm learning Kotlin and Compose Desktop and I'm trying refresh the UI before fetch data from an API.
But the request is running inside a runBlocking, thus the UI freezes until request is completed.
This is my code, everything works.
val client = HttpClient(CIO)
#OptIn(ExperimentalComposeUiApi::class)
#Composable
#Preview
fun App() {
var text by remember { mutableStateOf("Test button") }
Box(
modifier = Modifier.fillMaxSize(),
contentAlignment = Alignment.Center
) {
Column(
modifier = Modifier.padding(50.dp)
) {
Button(
onClick = {
text = "Wait..."//How to refresh UI to display this text?
runBlocking {
delay(5000)//blocking test
val response: HttpResponse = client.request("https://myapi.com/") {
// Configure request parameters exposed by HttpRequestBuilder
}
if (response.status == HttpStatusCode.OK) {
val body = response.body<String>()
println(body)
} else {
println("Error has occurred")
}
}
text = "Test button"
},
modifier = Modifier.fillMaxWidth()
) {
Text(text)
}
OutlinedTextField(
value = "",
singleLine = true,
onValueChange = { text = it }
)
}
}
}
fun main() = application {
Window(
onCloseRequest = ::exitApplication,
state = WindowState(size = DpSize(350.dp, 500.dp)),
title = "Compose test"
) {
App()
}
}
How to achieve that?

Answer 1

The problem here is that you are using runBlocking at all.
The most straightforward solution for your case would be to replace your runBlocking {} with a coroutine scope. At the top of your App() function, create your scope: val scope = rememberCoroutineScope(), then instead of runBlocking you can say scope.launch {}.
New code would be:
#OptIn(ExperimentalComposeUiApi::class)
#Composable
#Preview
fun App() {
var text by remember { mutableStateOf("Test button") }
val scope = rememberCoroutineScope()
Box(
modifier = Modifier.fillMaxSize(),
contentAlignment = Alignment.Center
) {
Column(
modifier = Modifier.padding(50.dp)
) {
Button(
onClick = {
text = "Wait..."//How to refresh UI to display this text?
scope.launch {
delay(5000)//blocking test
val response: HttpResponse = client.request("https://myapi.com/") {
// Configure request parameters exposed by HttpRequestBuilder
}
if (response.status == HttpStatusCode.OK) {
val body = response.body<String>()
println(body)
} else {
println("Error has occurred")
}
}
text = "Test button"
},
modifier = Modifier.fillMaxWidth()
) {
Text(text)
}
OutlinedTextField(
value = "",
singleLine = true,
onValueChange = { text = it }
)
}
}
}
I saw one comment say to use LaunchedEffect() but this won't work in your case since you can't use that in an onClick since it's not a Composable.