[Kotlin HTTP client] - Any recommendations for a client library? Mainly require for trying out concurrency locally in a sandbox environment console app. Noticed Ktor client, but there's no documentation as it's in progress.

Hi all, getting a little confused about an issue I’m having. Have implemented a Google Oauth process to connected to a user’s drive. Locally, in an emulator, everything works fine, but as soon as I try to test the app in Internal Testing/Closed Testing, the app crashes with this error:

java.lang.RuntimeException: 
  at android.os.AsyncTask$4.done (AsyncTask.java:415)
  at java.util.concurrent.FutureTask.finishCompletion (FutureTask.java:383)
  at java.util.concurrent.FutureTask.setException (FutureTask.java:252)
  at java.util.concurrent.FutureTask.run (FutureTask.java:271)
  at android.os.AsyncTask$SerialExecutor$1.run (AsyncTask.java:305)
  at java.util.concurrent.ThreadPoolExecutor.runWorker (ThreadPoolExecutor.java:1167)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:641)
  at java.lang.Thread.run (Thread.java:923)
Caused by: java.lang.IllegalArgumentException: 
  at com.google.api.client.repackaged.com.google.common.base.Preconditions.checkArgument (Preconditions.java:5)
  at com.google.api.client.util.Preconditions.checkArgument (Preconditions.java:10)
  at com.google.api.client.googleapis.auth.oauth2.GoogleClientSecrets.getDetails (GoogleClientSecrets.java:10)
  at com.google.api.client.googleapis.auth.oauth2.GoogleAuthorizationCodeFlow$Builder.<init> (GoogleAuthorizationCodeFlow.java:10)
  at com.jenix.lemmi.ui.splashscreen.SplashScreenActivity.getCredentials (SplashScreenActivity.java:10)
  at com.jenix.lemmi.ui.splashscreen.SplashScreenActivity.access$getCredentials (SplashScreenActivity.java:10)
  at com.jenix.lemmi.ui.splashscreen.SplashScreenActivity$AsyncGetCredentials.doInBackground (SplashScreenActivity.java:10)
  at com.jenix.lemmi.ui.splashscreen.SplashScreenActivity$AsyncGetCredentials.doInBackground (SplashScreenActivity.java:10)
  at android.os.AsyncTask$3.call (AsyncTask.java:394)
  at java.util.concurrent.FutureTask.run (FutureTask.java:266)
  at android.os.AsyncTask$SerialExecutor$1.run (AsyncTask.java:305)
  at java.util.concurrent.ThreadPoolExecutor.runWorker (ThreadPoolExecutor.java:1167)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:641)
  at java.lang.Thread.run (Thread.java:923)

From my understanding, it’s possibly due to Oauth credentials not matching - I’m using the SHA-1 signing key from the Play Console, so not sure what else i’m missing, Any ideas?

Hi, Do i need to learn java before i start learning kotlin?

Hi. I'd like to check whether

null

property is exists in data class. Should I check for each property like as below? Or there is other good way?

data class Book(val name: String?, val author: String?, val price: Int?)

fun isExistNull(): Boolean {
    if (name == null || author == null || price == null) {
        return true
    }
    return false
}

I'm trying to do a Kafka tutorial in Kotlin and wondered what the following code is in idiomatic Kotlin

// send data - asynchronous
            producer.send(record, new Callback() {
                public void onCompletion(RecordMetadata recordMetadata, Exception e) {
                    // executes every time a record is successfully sent or an exception is thrown
                    if (e == null) {
                        // the record was successfully sent
                        <http://logger.info|logger.info>("Received new metadata. \n" +
                                "Topic:" + recordMetadata.topic() + "\n" +
                                "Partition: " + recordMetadata.partition() + "\n" +
                                "Offset: " + recordMetadata.offset() + "\n" +
                                "Timestamp: " + recordMetadata.timestamp());
                    } else {
                        logger.error("Error while producing", e);
                    }
                }
            });
        }

I know that val cannot be reassigned, but how would I for example send a variable to a function to do something with it?

private fun resetCounterAndGame(counter: Int) {
    if (counter == 2) {
        gameButtonText.set(resProvider.getString(R.string.try_another_number))
        gameStarted = false
        counter = 0 <--- val cannot be reassigned of course
    }
}

what classA.instance means? equal to classA()?

Hi, All. I am learning Kotlin by hyperskill.org JetBrain Academy I getting this error when checking my solution but when running it in IDE it's working fine https://hyperskill.org/projects/83/stages/458/implement is this issue can be fixed by me or only by hyperskill JetBrain Academy The compile configuration has been deprecated for dependency declaration. This will fail with an error in Gradle 7.0. Please use the implementation configuration instead. Consult the upgrading guide for further information: https://docs.gradle.org/6.6.1/userguide/upgrading_version_5.html#dependencies_should_no_longer_be_declared_using_the_compile_and_runtime_configurations at build_bzr9s6nt7rztzjinzwhqs1atm$_run_closure1$_closure4.doCall(/mnt/sdb1/IntelliJIDEAProjects/Flashcards/build.gradle:23) (Run with --stacktrace to get the full stack trace of this deprecation warning.)

[CompletableFuture] I’m having issues converting CompletableFuture to a suspendable function as there aren’t any examples nor guides for it. Does someone know what is the proper way to handle this? I’m using the Java 11 Http client and creating a wrapper for calling an API.

suspend fun HackerNewsApi.fetchItem(id: Int): CompletableFuture<HttpResponse<String>> {
    return client.sendAsync(
        request("${this.domain}/v0/item/$id.json"),
        HttpResponse.BodyHandlers.ofString()
    )
}

I'm reading effective java and at some point it mentions WeakReferences which got me to searching if it exists in Kotlin as well. I've been using kotlin for about 2 years, but never had a need to use it. Is

WeakReference

something that's popular? Should I be using it in some typical situations of development? I understand that I won't be using the entire std-lib, but references are everywhere and so it seems like I should have come across a valid use of WeakReference by now (I mostly build android apps if it helps)

How do I search a top level function in intellij?

Is there a shorthand for:

(0..10).map { random.nextDouble() }

? Basically, I am looking for

repeat(n)

where the function can return a value:

newRepeat(10).map { random.nextDouble() }

All classes in java extend Object. All classes in Kotlin extend Any. Why is that?

What's the basic difference between Flow and Live data? Can anyone explain this with an example

message has been deleted

For example, how do I refer to other objects in the View by ID/CSS selector?

Hi. I have some troubles to do some transformations like extension of LiveData has one

LiveData<X>.map {} => transform type MutableLiveData<DomanType> -> LiveData<UiType>

I would like replace LiveData with StateFlow but i need to transform domain type to UI type that i have for each layers. Which one method i should use ? The same method "map" in Flow return Flow<R> but i need StateFlow<T>. I can also do transormation when i have data from useCase and then assign MutableStateFlow to StateFlow by invoking asStateFlow but its a little worse solution than i have with LiveData right now. Thanks for any advice. I found similar question here: https://github.com/Kotlin/kotlinx.coroutines/issues/2008

<<SOLVED>> Hi everyone! I’m new to Kotlin and functional programming, coming from Java OO. Here’s my question: If I want to define some interface method implementations using

runCatching

, something like this below, how should I define my interface method signature in order to return whatever the runCatching returns? I hope I was clear enough. Thanks in advanced

interface IMyInterface { 
    suspend fun myFunction()
}

class MyClass : IMyInterface {
    override suspend fun myFunction() = runCatching {

    }.onFailure { ... }.getOrThrow()
}

Hi, I am wanting to replicate a python feature

def myFunction(a,b,c): 
    return lambda x: a * x ** 2 + b * x + c

however I am not understanding what is wrong with

fun potentialEnergy(charge1, charge2, k){
    val x = {position: Double -> k * charge1 * charge2 / position / position} // creating lambda function
    return x
}

What is wrong with this lambda function expression.

General question, what are the process of making in concrete the app? I have my documentation on what the app does, its functionalities and then? Do i start with the database? Then make the layout? Then logic? And then the "front-end"? What is the correct process?

If sealed class is internal, so I don’t have to write internal modifier to his heirs, or not?

Message moved in #kodein, sorry for the wrong channel!

Is there a simple way to create a generic type-safe builder that can be used with a lambda? like

functionName<ClassName> { …className functions}

? I know it can be done specifically, but I was wondering if there was a way to create a generic approach. in Kotlin.

Could I get a quick code review please? Is the use of while-true and runBlocking OK here?

class WsClient {
    private val url = "<http://example.com>"
    private val httpClient = HttpClient { install(WebSockets) }

    suspend fun start() {
        httpClient.wss(HttpMethod.Get, url) {
            send("Hello")
            while (true) {
                when (val frame = incoming.receive()) {
                    is Frame.Text -> println(frame.readText())
                    is Frame.Binary -> println(frame.readBytes())
                }
            }
        }
    }
}

fun main() = runBlocking {
    WsClient().start()
}

Does it matter whether I extend

Exception

or

RuntimeException

in Kotlin? I thought it doesn't but my

Exception

extension is getting wrapped in

UndeclaredThrowableException

when interacting with a Java library.

Hello, can anyone help with how I might handle timeouts/ errors when I try and connect to an offline database using the exposed framework > Database.connect

hi guys, I have a performance question to ask. I’m working with IntArray (for efficiency) but then at some point I want to convert that to a list. I can use

.toList()

method no problem but then when I check for efficiency the blame graph tells me that tolist() is not that efficient. Anything I’m missing? Any suggestion?

Android Studio is giving me a warning that I should use Java 11. I have installed it here: /Library/Java/JavaVirtualMachines/jdk-11.0.9.jdk Can you please explain how I can configure Android Studio (or my app) to use it?

What is the kotlin way to handle thread safety/concurrency? (instead of using synchronized like Java) I am thinking to create a top-level object by call newSingleThreadContext() and pass it around to make sure the operation to change given object all come from same thread. Is this usually how we do in Kotlin?