5,064 questions
2
votes
1
answer
77
views
.flowOn(Dispatchers.Main) blocks the main thread
Why does this code block indefinitely?
fun main() = runBlocking {
val myFlow: Flow<String> = flow {
emit("abc")
}.flowOn(Dispatchers.Main)
myFlow.collect {
...
- 23
0
votes
1
answer
152
views
MutableSharedFlow.emit() hangs forever
In our project we are observing an issue with consuming the data from MutableSharedFlow. Under certain conditions we are cancelling the scope in which we produce and collect data. Then we launch data ...
- 1
Best practices
3
votes
0
replies
40
views
Testing with corroutines
Let's say I have Worker class and I want to do long running tasks in the background until user stops it or it is cancelled. It changes state of the class while doing the work and I want to write tests ...
- 11
4
votes
1
answer
105
views
Does combine conflate flows?
When I use combine() on two flow, it's not supposed to conflate/skip values. But when I collect a combine of 2 flows in a Coroutine, some values are randomly skipped.
Link to the kotlin playground : ...
- 382
0
votes
2
answers
62
views
Why is my continuous flow test code flaky?
I am trying to test the number of times a Flow is collected -
runTest {
var count = 0
backgroundScope.launch(UnconfinedTestDispatcher(testScheduler)) {
dao.getEntities().collect {
...
- 1,242
4
votes
2
answers
162
views
How to call a composable function after a certain time in Jetpack Compose?
When my application starts, I launch an animation. Now I would like to switch to another component (navbar) after 30 seconds. In my research, I saw that the delay function from the Kotlin Coroutines ...
- 41
0
votes
0
answers
73
views
How does async exception propagation rally works?
I’ve read in multiple places that async can swallow exceptions if we don’t call await, but as far as I can see, it almost always throws them regardless of whether await is used or not.
For example, ...
- 13
0
votes
0
answers
31
views
Use suspend function with Vert.x Kafka Consumer?
I want to use suspend function in a handler for KafkaConsumer.
This is what I have so far, but I'm not sure about exception handling.
CoroutineEventBusSupport would call fail() on the message and ...
- 3,313
-2
votes
2
answers
130
views
Waiting for coroutine to end it's job to trigger an event [closed]
I have an Activity that is responsible for creating a new entry in the database. In this activity, a button launches a coroutine to do all the database-related stuff, and when it's done, navigate to ...
3
votes
0
answers
194
views
Objectify with Kotlin Ktor 3.3
Objectify v6.1.3
With Kotlin and Ktor 3.1, I was calling ObjectifyService.begin() within the init {} block of my request handler base class and then closing that context once the request was finished. ...
- 8,864
1
vote
1
answer
87
views
Differences between long-running Flow processing with transform() and flatMapLatest()
I have a data stream coming from the server. The server does not provide any information about when the next piece of data will arrive. I have a Flow in my repository that emits data as it arrives. ...
- 7,869
0
votes
3
answers
152
views
Are there any real difference between GlobalScope and CoroutineScope?
I'm trying to understand the difference between the 2.
If a CoroutineScope is not tied to any lifecycle-aware component, then I think they behave the same:
If Im not passing any context to ...
- 13
0
votes
1
answer
66
views
Is kotlin coroutine Job's status is reliable for concurrency control?
I've read this sentence in the Java Concurrency in Practice book that:
The result of Thread.getState should not be used for concurrency
control, and is of limited usefulness for testing—its primary ...
2
votes
1
answer
96
views
How can I tie a coroutine's lifetime to the lifetime of an object?
I have some code similar to this:
class Foo {
var x = 0
init {
GlobalScope.launch {
while (true) {
delay(1000)
x += 1
}...
- 216
0
votes
1
answer
185
views
Strictly depending on Coroutine 1.8.1 to use BroadcastChannel with Kotlin 2
I have a code base which is tightly coupled with BoradcastChannel and I can't update that for now. But I want to upgrade the dependencies to their latest, use kotlin2 and compose.
I have changed my ...
- 1,047
0
votes
1
answer
39
views
Creating activity prevents spinner from spinning in Android
I have 2 activities in my app. When another one is called there is a spinner but it doesn't spin. I think it may be because the main thread is stuck.
I moved all background tasks to Dispatchers.IO, ...
5
votes
0
answers
153
views
Why is the action of Mutex.withLock not marked as suspend?
The action parameter of the withLock function is a lambda without the suspend keyword. Is there a reason for this missing keyword?
In most cases, this lack of the suspend keyword isn't an issue ...
1
vote
2
answers
187
views
Testing a function that creates a coroutine scope inside it
I have something like the following in Kotlin:
class A {
fun a(): Unit = TODO()
}
fun foo(a: A) {
// Do something
CoroutineScope(Dispatchers.IO).launch {
delay(1000)
a.a()
...
- 8,403
2
votes
2
answers
102
views
Deadlock when withContext() is combined with logging in object initializer
Consider the following Kotlin object:
package com.example
import org.slf4j.LoggerFactory
import java.lang.Thread.currentThread
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines....
- 5,470
0
votes
1
answer
72
views
Jetpack Compose `LazyColumn takes` ~3 to ~4seconds to reflect `mutableStateListOf` mutations even though `Flow` emits immediately [closed]
I switch between “chart windows” (weekly, monthly…). Upstream data is a hot Flow (think Room).
To keep the list size stable, I render 30 fixed slots: real items in the first n, placeholders in the ...
2
votes
1
answer
65
views
Implement same task for two different user interfaces in Kotlin [closed]
I am working on a program which has both a TUI (terminal user interface) as well as a GUI (graphical user interface).
The program has some functions which take quite a long time to complete (waiting ...
- 356
0
votes
1
answer
107
views
Why does Android prohibit running IO-performing coroutines from the main thread? [closed]
Context and prior understanding:
In Node.JS, I/O code is run in a thread pool / event loop parallel to the main JavaScript thread. async code is never truly blocking per-se, unless a blocking call (e....
- 697
2
votes
1
answer
74
views
Unclear execution order of Kotlin coroutines
Why the output of this code is so unpredictable?
suspend fun main() {
val job1 = GlobalScope.launch {
delay(1000L)
println("World!")
}
val job2 = GlobalScope....
- 21
0
votes
1
answer
62
views
SharedFlow emmited in another scope in a separated class is not collected
I have a Bluetooth tracker app. I try it to be clean. Everything related to scan is encapsulated in one class. I am injecting with Hilt.
The problem is when I scan via Bluetooth for 10s, I emit the ...
- 59
0
votes
0
answers
44
views
Missing MDCContext from kotlin web flux
I have a spring web flux based application, written in kotlin I am adding few information in reactor context by using web filter. I also have logging information which I set in MDCContext but I am ...
0
votes
1
answer
110
views
Problems with Ktor receiving multipart: Flow invariant is violated
I am rather new to Ktor and try to upload a file to my server. This is the route:
fun Application.module() {
install(ContentNegotiation) {
json()
}
routing {
post("/upload") {
...
- 698
1
vote
1
answer
68
views
Why this code in Android onCreate is not Failing
So, I am aware of the fact that in Android, views cannot be updated from a background thread.
I have a TextView called appTitle.
I am launching a coroutine on background thread ( IO ) and on that ...
- 300
2
votes
1
answer
244
views
Kotlin' coroutines and retrofit2: Program blocks for one minute after getting http response
I need to use Kotlin' coroutines and the retrofit2 library to make http requests.
When I run the following code, the http request works as expected (posts is printed), but after this, the program ...
- 293
1
vote
1
answer
63
views
List of Stateflows not detecting changes
I am using the MVVM model and have come across a problem with Stateflow that I cannot find a solution. Perhaps I am approaching the problem in the wrong way.
Each of my Models responds to a specific ...
- 11.8k
0
votes
1
answer
42
views
error handling and Structured concurrency in corutin
i have this code my viewmodel init
val scope = CoroutineScope(Dispatchers.Main )
var child1:Job = Job()
var child2 : Deferred<Unit> = CompletableDeferred(Unit)
child1 =scope....
- 59
1
vote
0
answers
143
views
Spring Security SecurityContext not propagating to Kotlin coroutines - getting UNAUTHORIZED
Problem
I'm using Spring Boot 3.3.3 with Spring Security and Kotlin coroutines. My authentication filter successfully authenticates the user and sets the SecurityContext, but when I use suspend fun in ...
- 48
0
votes
1
answer
117
views
Ktor/Exposed TransactionManager.currentOrNull() not null after closing newSuspendedTransaction block when block contains delay()
I’m looking for some insight into this issue I’m having with my Ktor/exposed application…
If I do the following in a KTOR route, after the newSuspendedTransaction block is closed, TransactionManager....
- 2,584
2
votes
2
answers
109
views
async await: Calling .await() on Deferred immediately - Correct?
These code is from a Udemy-course, which I'm following currently:
fun getWeatherData() {
viewModelScope.launch(exceptionHandler) {
uiState = try {
val ...
- 791
-1
votes
2
answers
161
views
Unit testing a broadcast receiver with callbackflow
I have the following class I am trying to test. I am using mockito as that is the library I am using
class ConsentUpdatedBroadcastReceiverImp @Inject constructor(
private val context: Context,
...
- 22.7k
1
vote
1
answer
109
views
Using a flow to observe the onReceive of a broadcastreceiver and emit some value that can be observed
I have the following BroadCastReceiver. I inject a 3rd party library and have to call a method on it to get a result each time the onReceive is called. I need to observe this changes from our ...
- 22.7k
1
vote
2
answers
239
views
How to unit test a withtimeout block
I have this block:
try {
withTimeout(200) {
val response = datafetcher.fetchData(request)
}
} catch (TimeoutCancellationException e) {
returns response with some error message added
}
I am ...
- 21
0
votes
1
answer
59
views
Room RawQuery in Compose: Cannot access database on the main thread. Need to return a Flow<List<MyEntity>>
I need to return a Flow<List<MyEntity<>> from Room @RawQuery in Compose but get runtime error: Cannot access database on the main thread.
I have found many posts for @Query about using ...
- 171
0
votes
1
answer
46
views
Why does this code crash when i am passing the scope created from viewmodelScope which is a supervisorScope?
// code inside viewModel
viewModelScope.launch(Dispatchers.IO) {
try {
tempUsecase.coroutineTest(
coroutineScope = this,
)
} catch (e: Exception) {
...
0
votes
1
answer
101
views
viewModelScope not working after Composable is revisited using Navigation in Jetpack Compose
So, i have a composable, a viewmodel and a repository. I am fetching data from Firebase's Firestore, and it already has some documents in the collection i am fetching from.
These are the snippets of:
...
1
vote
1
answer
84
views
How do you test code that uses withTimeout?
I have a code that uses withTimeout as follows.
suspend fun send(timeoutMillis: Long): Int? {
val result: Int? = withTimeoutOrNull(timeoutMillis) {
doSomething()
}
return result
}
suspend ...
- 11
0
votes
1
answer
22
views
SharedFlow builder
I have suspending function, which returns a hot flow.
suspend fun createFlow(): SharedFlow
How can I build another SharedFlow, which calls createFlow lazily (i.e. as only first subscriber connects to ...
- 3,202
2
votes
1
answer
198
views
Why is CoroutineContext element null via kotlin.coroutines.coroutineContext in tests (Kotest/Dispatchers.Default) but not production?
I'm encountering a discrepancy in retrieving a custom CoroutineContext.Element (TraceContextElement) depending on the environment (test vs. production) and how I access the context within a launched ...
- 21
3
votes
2
answers
318
views
How to spawn new coroutines for the processing of each element in a cold flow?
Came across an example that simulates accessing a slow database to obtain a flow of user identifiers which is associated with a profile that's accessible via an even slower network resource:
fun ...
- 153
0
votes
1
answer
76
views
Managing sequential callbacks with Kotlin
There is a very common pattern when dealing a remote service: A sequential series of calls to the service, each of which invokes a callback, asynchronously, when complete. I believe, for instance, ...
- 6,705
0
votes
2
answers
120
views
Android Jetpack Compose: How to stop execution of a coroutine launched in `produceState`?
Goal
I have a computation heavy function calculateItems: suspend (String) -> Sequence<String>.
I want to load the outputs of this calculation while showing the progress to the user and ...
- 341
0
votes
1
answer
288
views
How to update UI state using stateIn in ViewModel jetpack compose
I have a ProfileViewModel where I load the user profile when the user lands on the screen. To achieve this, I use stateIn so that the profile is fetched automatically.
Now, I want to modify ...
- 7,869
1
vote
1
answer
130
views
How to build list from async tasks properly in Kotlin
I have function like this
fun getUsersList(userIds: List<String>): List<User> {
val list = mutableListOf<User>()
userIds.forEach { id ->
getUserFromDatabase(id) {...
- 137
1
vote
0
answers
59
views
Some coroutines shenanigans in a custom flow operator with select clause
I have the following flow operator:
fun <T> Flow<T>.bufferedWithTimeout(
maxBufferSize: Int,
timeout: Duration
): Flow<List<T>> {
require(maxBufferSize > 0) {
&...
- 1,060
0
votes
1
answer
173
views
How to prevent coroutine scope cancellation on async failure without using a supervisorScope?
I’m working with a regular CoroutineScope (not a supervisorScope). I’ve noticed that when I launch an async block inside this scope, and it throws an exception—even if that exception is caught outside ...
- 6,040
1
vote
1
answer
100
views
ConflatedBufferedChannel onUndeliveredElement behavior
org.jetbrains.kotlinx:kotlinx-coroutines-core:1.10.1
ConflatedBufferedChannel with capacity = 1.
If onBufferOverflow is configured as BufferOverflow.DROP_OLDEST
trySend returns success.
...
- 1,309