Is there any replicate function in Kotlin? replicate(nInt,xT):List is a list of length n with x the value of every element. I wrote a mutable version replicate as below: fun mutableReplicate(n:Int, x:T) : MutableList{ val xs = mutableListOf() for (i in 1..n){ xs.add(x) } return xs } Is there any bulid-in immutable replicate function in Kotlin? How to write ourselves an immutable replicate function in Kotlin?

@coder has left the channel

Why there is NoClassDefFoundError with the class is really exist? I occur an odd NoClassDefFoundError, because the "NoClassDefFound's class" is really exist: Fatal Exception: java.lang.NoClassDefFoundError: cn.dreamtobe.babyguard.b.a$e at cn.dreamtobe.babyguard.data.BabyGuardDatabase.repealLastAction(BabyGuardDatabase.kt:109) at cn.dreamtobe.babyguard.data.BabyGuardDatabase$show$1.onClick(BabyGuardDatabase.kt:192) at...

Will if / else become an expressions in typescript / javascript at some point? I really like this feature in Kotlin: In Kotlin, if is an expression, i.e. it returns a value. // As expression val max = if (a > b) a else b (from https://kotlinlang.org/docs/reference/control-flow.html) Is this also planned for typescript / javascript?

How to save picture(bytes) to path(server) with Golang and Android(kotlin) I have a problem, i'm trying to save a picture/file wich is bytes and with that data I want to save to path "/pictures" , it saves but I can't open because it says it can open the file, maybe because the data is wrong I don't know. But size of file it semms right, if I change the quality of picture, the size changes. I'm uploading with android app (kotlin). Code in golang to receive request body and save file to path func uploadHandler(w http.ResponseWriter, r *http.Request) { data, err...

Android google maps shows the default marker icon behind the custom image I have set I have added Google Maps API on my android application which I created using Kotlin programming language. I am trying to add a marker with a custom image bitmap to my GoogleMap using BitmapDescriptorFactory.fromResource(Int), But when I run the app, it adds the marker with the default icon then just puts my icon on it. And when I click on the marker it bring the default icon to front and send my icon to the back....

Kotlin infinity loop on list in recursion This follows infinite loop, in clojure such things just fine tailrec fun passHeaders (xH: List) { while (xH.isNotEmpty()) { passHeaders(xH.drop(1)) } }

Kotlin: Pass and consume a 2 parameter function? I'm trying to learn functional programming in Kotlin and am having difficulty making this code work: import java.util.* fun caseName(br: String, c: Int): String { if (c == 0) { return br.toLowerCase() } else { return br.toUpperCase() } } fun mapIt(ns: ArrayList, f: (String, Int) -> String): List { val coll: List = ns.map {it -> f(it, _)} return coll } fun main(args: Array) { val names = arrayListOf("Joe", "Bill", "Murrary") val cased = mapIt(names, (::caseName)(_,...

Playing audio files from desired folder I have 5 folders and every folder contains 5 audio files. When Someone clicks on a folder, The program should start playing all the audio files from that folder. I am new to android, So i have a very little Idea about it. I tried doing it, but it shows all the audio files together. I want it to show folder wise. fun abs(){ var songsURI = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI var selection = MediaStore.Audio.Media.IS_MUSIC + "!=0" val cursor =...

Adapter Class for this Code //I want to display audio files from every folder and play all files. I want to know the adapter for this code data class SongInfo(var songURL: String, var songAuth: String, var songNAme: String) data class DirInfo(var dir: String, var songInfo: ArrayList) private fun getAudioDirectories(): ArrayList { var result = ArrayList() val directories = LinkedHashMap() val uri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI val selection = MediaStore.Audio.Media.IS_MUSIC + "!=0" val order =...

Which is the preferred solution for Kotlin koan &amp;quot;Partition&amp;quot; and why? I worked through the Kotlin koan Partition and came wound up with this, which passes the unit test: fun Shop.getCustomersWithMoreUndeliveredOrdersThanDelivered(): Set = customers.filter{it.orders.partition{it.isDelivered} .let{(delivered, undelivered) -> delivered.size < undelivered.size}}.toSet() This is a variation on the solution: fun Shop.getCustomersWithMoreUndeliveredOrdersThanDelivered(): Set = customers.filter { val (delivered,...

ArrayBroadcastChannel: second subscriber doesn't update UI In my code, I have an ArrayBroadcastChannel that sends strings to two subscribers: val channel = ArrayBroadcastChannel(1) ... launch(viewModelJob + CommonPool) { val reader = BufferedReader(InputStreamReader(bluetoothSocket.inputStream)) while (viewModelJob.isActive) { reader.readLine()?.let { channel.send(it) } } } ... launch(job + UI) { dataStream.consumeEach { if (it.isNumber()) { val coloredValue = asyncGetColoredValue().await()...

Is intersection casting possible in Kotlin? I have a method in Java like so: public methodName(T arg, ...) where A is a class and B is an interface. In my kotlin class, I have another variable of type C, and I wish to achieve the following: if (variable is A && variable is B) { methodName(variable, ...) } else { // do something else } Is it possible to properly cast variable so that it may be used as an argument without errors? Currently, the variable has a setter method, so smart casting isn't available. However, I...

NullPointerException in Kotlin When I write this code in kotlin activity var tv: TextView = findViewById(R.id.tv_kotlin) as TextView It always crashes with the following error: Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference And I find when I convert my Java codes to kotlin codes,the auto converter always does like this: private var btn: Button? = null And when I use the reference, I have to put...

How to properly handle a null variable perspective in kotlin? My old java version method looks like: @Override public void closeSimpleAlertDialog() { if (mAlertDialog != null && mAlertDialog.isShowing()) { mAlertDialog.dismiss(); } } As you can tell it is checked whether the null reference link to a dialog mAlertDialog and if not null check call method isShowing(), and only then caused a method of close - dismiss(). Very simple I faced a problem - how is still in "Kotlin-style" to perform the same operation? My first version looks...

Confused about RxJava variable Assignment I have a function that takes in a username String and returns whether or not the user already exists in a MongoDB database. I'm new to the RxJava and Retrofit model, and I'm confused about hwo to assign variables once I subscribe to the Observable object. fun handleUsername(username: String): Boolean { var userExists = false UserServiceProvider.getUserService().getUserByUsername(username) .subscribeOn(Schedulers.newThread())...

What is &amp;quot;implementation&amp;quot; in Kotlin Gradle dependencies? I'm using Android Studio 3.0 Preview to start new Kotlin project. As I try to add dependencies in build.gradle I saw implementation scope instead of usual compile. androidTestImplementation('com.android.support.test.espressoespresso core2.2.2', { exclude group: 'com.android.support', module: 'support-annotations' }) implementation 'com.android.supportappcompat v725.3.1' testImplementation 'junitjunit4.12' There's also androidTestImplementation and testImplementation scope. In...

Android Studio 3.0 Kotlin changes are not reflected in the build Has anyone tried the new android studio with 3.0 for kotlin. I am seeing a weird issue where the Kotlin code changes are not reflected when I run the app but the java changes can be seen. When I debug the app, the code won't stop at the new lines of code. Also I've particularly seen that during runtime Java complains that the new method that I wrote in Kotlin cannot be found.(But the java code which was written at the same time can be seen) The only solution I've found is either to rebuild...

Call Kotlin object with class delegation from Java as a static method This may be a bit difficult to describe, so I'll try to give a concrete example of what I'm trying to do. Suppose we have a Facade interface and class (in java), like this: interface FacadeInterface { void method(String from, String via); } class Facade implements FacadeInterface { private Class mClazz; public Facade(Class clazz) { mClazz = clazz; } @Override public void method(String from, String via) { System.out.println("Method called from " +...

Creating a new project in Android studio supports Kotlin eroor I am very new to Kotlin and I am creating a new project that supports Kotlin in Android Studio 3.0 canary. This project is having two issues. The R file is not getting resolved The package name must be a '.' separated identifier list What should I do now? Thanks in advance.

Why I cannot refer to inner object from val or typealias referring to an object? The question is simple. object SomeObjectA { object SomeObjectB { val a = "test" } } val X = SomeObjectA typealias Y = SomeObjectA SomeObjectA.SomeObjectB // works X.SomeObjectB // error Y.SomeObjectB // error I cannot refer to an inner object (in an outer object) using val or typealias which are referring to the outer object. Why?

Kotlin: Sorting | Location of swap operation I'm implementing the Quicksort algorithm in Kotlin. For that, I created an interface, ISort, with a type parameter and a single function, sort. For sorting, I need the swap operation. I was wondering what the best location of this swap function is. My ideas: 1) Unfortunately, in Kotlin one cannot make interface function protected. Thus, every class could see the swap in its implementations and that's not too nice (although it's not too bad either, I agree). 2) Putting it in the QuickSort...

Kotlin bound callable references inconsistency today I was creating unit tests for my Presenter in Android app and I noticed some inconsistency with bound callable references. Is it under development or is it language bug? I found that in kotlin 1.1 bound callable references are supported. But my code fails with kotlin 1.1.2-4. In my presenter class, tested method reads data from database and dao.getAllItems() method have no parameters while view takes list -->...

Passing application to AndroidViewModel I would like to use AndroidViewModel for my view model in order to get access to the Context. It requires Application to be passed as a parameter. My ViewModel class looks like this: class FooAndroidViewModel(application: Application?) : AndroidViewModel(aplication) { ... } It is getting instantiated like this: val fooModel =...

Calling kotlin functions which are keywords in java from java? Since new is not a keyword in kotlin, i can have the following function in kotlin. fun new(): String { return "just returns some string" } But i am unable to call this function from java since new is a keyword in java. I would like to know if there is some alias for this function in java realm. I did not find any intellij suggestions that might be a possible alias to this function.

What's the earliest Android API level I can use Kotlin with? I think the question is pretty clear but what's the earliest API level I can target on Kotlin?

Custom Layout Behavior How can I acheive such behavior for bottom bar? It works like scroll aware behavior for floating action button but when the recyckerview scrolls to the bottom, then it pulls that panel up (like the last element in the recyclerview is that panel). I don't think that the developer duplicated those views. Maybe it is possible to extend behavior somehow? Here is the code for scroll aware behavior: class ScrollAwareBehavior :...

An open Kotlin class cannot be seen from Java I'm migrating a Spring project to Kotlin, this is my current configuration: kotlin-maven-plugin org.jetbrains.kotlin ${kotlin.version} spring 1.8 compile process-sources compile...

Scaling down a child view takes same height I am trying to display texts in a TextView in NestedScrollView such that texts bigger than the screen get displayed after scaling down the TextView it self. Here is my code - val content = findViewById(R.id.content) as TextView content.setText(R.string.large_text) content.viewTreeObserver.addOnGlobalLayoutListener { Log.d("Height", content.height.toString())//1584:6501 val factor = 1584f / 6501; content.scaleX = factor;...

Kotlin in Android Studio. Function average() on Array doesn't work I decided to write the first class in my project in Kotlin. I see in doc that there is average function on array and iterable http://apimirror.com/kotlin/api/latest/jvm/stdlib/kotlin.collections/-iterable/index So I wrote code like that: val numbers: IntArray = intArrayOf(11, 20, 30, 40, 50) val average: Float = numbers.average() It works in try.kotlinlang.org, but...