Kotlin: Destructuring in lambda parameters Is there a way to iterate over a list of objects/pairs like so: val list = listOf(Pair(1,2),Pair(2,3)) list.forEach { first, second -> first + second } Following doesn't work either: list.forEach { (first, second) in it -> first + second }

Kotlin: How to handle function of Any input type and given output type I have functions with signature (ShellInput) -> ShellOutput. Reference to these is stored in a map: mutableMapOf ShellOutput>("trim" to ::trim) These are then fetched from this map and invoked via reflection. Now there's a need to have functions where input type can vary, so I tried: mutableMapOf ShellOutput>("trim" to ::trim) But this does not work.

Dagger's module doesn't work after conversion from Java to Kotlin I create simple application for Android with Dagger 2. It has one shared object and one module. The module is: @Module public class MyModule { @Provides @Singleton public Hren providesHren() { return new Hren(); } } This module works. But when I convert it to Kotlin, I get compile time error:

Task appcompileDebugJavaWithJavac

...../DaggerMyApplicationComponent.java26 error: cannot find symbol...

Strange java.lang.ClassCastException when using [] call I'm using LibDGX library for my game. And i faced common exception ClassCastException, but it occurs in strange case. I'm using Animation class from LibGDX library. I'm getting error on...

How to get ResultSet string array? I have a query that is hitting a table that has an array column. When I am processing my records I would like to take the array column's data and treat it like a string array and grab the first value. I had assumed I could do the following: while (resultSet.next()) { val clients = resultSet.getArray("clients") println(clients[0]) } But when I do this I get the error: Error:(34, 3) Kotlin: Unresolved reference. None of the following candidates is applicable because of...

Google Places AutoComplete API gives API_NOT_CONNECTED error in Instant Apps configuration I am trying to add Google Places AutoComplete API to my Android Instant Apps project. I followed this sample to implement the API. My PlacesAdapter class: package net.epictimes.uvindex.autocomplete import android.content.Context import android.graphics.Typeface...

Android dagger 2 - Members injection methods may only return the injected type or void I'm use dagger 2 on my android/kotlin project. I was add ContentComponent and has own scope with ContentScope for lifecycle reason. My project works correctly until when I was add the ContentComponent. When I was build my project I getting this error: e: example\di\component\AppComponent.java9 error: Members injection methods may only return the injected type or void. e: e: public abstract example.di.component.ContentComponent...

Data class inheriting from Java class I have a data class in Kotlin that inherits from a Java class, which defines a constructor with 1 argument, public BaseClass(String userSessionId) { this.userSessionId = userSessionId; } My Kotlin class is defined as this class DerivedClass( userSessionId: String, var other: Other? = null ) : BaseClass(userSessionId) { I can't define it as a data class because of userSessionId, which Kotlin requires to be a val or var in data classes. However, if I do so, then Retrofit...

Thread-safe Global Resource in Android with Kotlin I'm new to Android apps and the activity lifecyle seems to force reliance on globals. (Even with Dagger there are stateful, global Dagger objects that perform dependency injection.) I'd like to make a globally available mode object called GlobalMode. The mode should be changeable at runtime. This is what I have so far: interface Mode { fun doSomething(a: Int); } class NormalMode : Mode { override fun doSomething(a: Int) { // ... } } class DebugMode : Mode {...

Best way of handling multiple object instances Due in part to the fact that I cannot create data classes without parameters in Kotlin, I use objects for those cases, e.g. sealed class Node { object Leaf : Node() data class Branch(val left:Node, val right:Node) : Node() } The issue is that sometimes, I end up with multiple instances of the Leaf class. Obviously this should not generally happen, but it occurs when serializing and deserializing with some frameworks and with some test cases. Now, you might argue that I should fix...

Android video recorder: failed to get surface Hi i am trying to use the camera v2 api to record video using a Raspberry pi 3 device that uses the raspberry pi camera module attached to it. I am developing this using Android Things with kotlin. Here is how my video recording code looks like. override fun startRecording(videoCameraCallback: VideoCameraCallback) { val cameraIdList = cameraManager.cameraIdList cameraManager.openCamera(cameraIdList[0], cameraStateCalback, null) Log.d("JJJ", "start recording called") }...

Add kotlinx-html-js to kotlin/js project in intellij I need to add kotlinx-html-js library to a kotlin/js project created with Intellij. I've tried to add maven support and in the pom.xml file write the following: 4.0.0 com.cillario Demo 1.0-SNAPSHOT jcenter jcenter https://jcenter.bintray.com org.jetbrains.kotlinx kotlinx-html-js ${kotlinx.html.version} As explained <a...

Filter rxjava not work i recently learning RxJava. I am learning about operator. This is my code : tvText = findViewById(R.id.tvText) val observable2 = Observable.just(1, 2, 3, 4, 5, 6) observable2.filter { i -> //filter genap i!! i % 2 == 0 } tvText.setOnClickListener { observable2.subscribe(object: Subscriber() { override fun onNext(t: Int?) { Toast.makeText(this@MainActivity, t.toString(), Toast.LENGTH_SHORT).show() } override fun onError(e: Throwable?) {...

Is Application() a Class or a function in Kotlin? I'm a beginner of Kotlin, the follow sample code is from a webpage. I think that Application() is a class, and UIApp is inherited from the class Application(). But in Android Studio 3.01, the hint of Application() is displayed as a Method, you can see the iamge, it make me confused! The Image of the hint in Android Studio 3.01 class UIApp : Application() { companion object { var instance: UIApp by...

How to specify parametrized generics for Kotlin property? I have a method in Kotlin that looks like this: fun addEventListener(eventClass: Class, eventHandler: EventHandler) { eventListeners.put(eventClass, eventHandler) } Also I have a property eventListeners but I can't figure out how to define it so it will have the same generic type, kinda like this private val eventListeners = HashMap() Obviously T is not defied for the property eventListeners and that is what I'm struggling with. Just so everybody knows, I understand that T...

How to design a complex class which incude some classes to make expansion easily in future in Kotlin? I'm a beginner of Kotlin, I use Code A to define a complex class MDetail, and use Code B to create a object aMDetail1, it can work. But the data construction is too bad to expand, if I include a new data class such as ScreenDef in MDetail just like Code C, all old code have to be rewriten. Is there a good data construction for a complex class which include some classes ? I hope to the data construction can be expansion easily in future! Code A data class BluetoothDef(val...

Is there an Kotlin equivalent `with` function in Swift? In Kotlin, we could change the below // Original code var commonObj = ClassCommonObj() commonObj.data1 = dataA commonObj.data2 = dataB commonObj.data3 = dataC // Improved code var commonObj = ClassCommonObj() with(commonObj) { data1 = dataA data2 = dataB data3 = dataC } However in Swift as below, do I have equivalent with function to use? // Original code var commonObj = ClassCommonObj() commonObj.data1 = dataA commonObj.data2 = dataB commonObj.data3 = dataC

Swift - Exit outer function from closure In Kotlin, you can return from an outer function from a closure. fun main(args: Array) { val letters = listOf("A", "B", "C") fun lookForLetter(letter: String, letters: List){ letters.forEach { l -> if (l == letter) { println("Found") return } println(l) } println("Completed") } lookForLetter("A", letters = letters) } Output: Found In Swift, return exits execution of the closure...

kotlin test whith mockito: comparison Failure I am trying to cover with test simple presenter, which looks like next: class Presenter{ fun getData(params:SomeParams) { usecase.execute(getObservable, params) } private fun getObservable() = object :DisposableObserver{ override fun onComplete() {} override fun onNext(t:SomeData) {} override fun onError(e: Throwable) {} } } here is my simple test: @Test fun getContacts() { presenter.getData() var observer =...

What is generateStubs for in Kotlin? Question 1 : What is generateStubs for in build.gradle? kapt { generateStubs = true } Question 2 : I didn't define apply plugin: 'kotlin-kapt' in my build.gradle but below code is working on my Android project. I wanna know why. apply plugin: 'kotlin-android' dependencies { ... kapt "com.jakewhartonbutterknife compiler${butterKnifeVersion}" ... }

How to position dialog to the bottom I am trying to set the dialog to the bottom but couldn't able to do that. It showing the top of the page. XML:

Gradle Kotlin DSL: Only use a single variable to define Kotlin version For describing Gradle build scripts, we can use Kotlin via build.gradle.kts files. It's a common problem to globally define the Kotlin version to be used, both in the dependencies and also in the build plugin section. Consider the following code (Gradle 4.3.1): plugins { var pluginVersion = "1.2.0" kotlin("jvm").version(kotlinVersion) // more } var dependencyVersion = "1.2.0" dependencies { compile(kotlin("stdlib", kotlinVersion)) compile(kotlin("reflect",...

Android reCaptcha closing listener I invoke the reCaptcha test (it floats AlertDialog with the text "Confirm that you are not a robot"), and I can close this AlertDialog by clicking on the screen around AlertDialog, or on the "Back" button, while reCaptcha works in the background, and can work addOnSuccessListener() , when you do not expect it. All used anything, but there is no listener, in case of closing reCaptcha.

What is the purpose of empty class in Kotlin? I was going through Kotlin reference document and then I saw this. The class declaration consists of the class name, the class header (specifying its type parameters, the primary constructor etc.) and the class body, surrounded by curly braces. Both the header and the body are optional; if the class has no body, curly braces can be omitted. class Empty Now I'm wondering what is the use of...

Kotlin generic type, Type inference failed Kotlin reference document said this example is valid. https://kotlinlang.org/docs/reference/generics.html#upper-bounds fun cloneWhenGreater(list: List, threshold: T): List where T : Comparable, T : Cloneable { return list.filter { it > threshold }.map { it.clone() } } But in Android studio 3.0, it shows thin red line under it.clone(). And error message is: Type...

Heroku postgres relation &amp;quot;information_schema.session_state&amp;quot; does not exist I am trying to move Ktor backend to Heroku postgres db. Here whole application code: https://github.com/MarcinMoskala/KotlinAcademyApp/tree/master/backend To move to Heroku postgres, I based on this example project: https://github.com/orangy/ktor-heroku-start I changed my database configuration to...

Kotlin function: Required Unit? Found Int Repeatedly facing this issue in Kotlin fun test(){ compute { foo -> Log.e("kotlin issue", "solved") } // This line is //showing error } fun compute(body: (foo:String) -> Unit?){ body.invoke("problem solved") } I am getting the error in Studio. Here is a screenshot.

How to get Data from java Rest API in android? i want to extract list of employee and their salary from a java Rest API using JSON in android.i am new in android please help.

Multithreading using Kotlin Coroutines I'm experimenting with Kotlin Coroutines and have following code: fun main(args: Array) = runBlocking { val cores = Runtime.getRuntime().availableProcessors() println("number of cores: $cores") val jobs = List(10) { async(CommonPool) { delay(100) println("async #$it on thread ${Thread.currentThread().name}") } } jobs.forEach { it.join() }...

Listening to messages and writing commands on an observable flow I have a method that opens a connection (Single) and another one that returns bytes (Observable) which must be written to the connection when open: interface Connection { fun read(): Observable fun write(command: Byte) } fun openConnection(): Single // opens a single connection fun toBeWritten(): Observable // output messages from elsewhere Problem: I want to make an observable flow that reads incoming messages and at the same time subscribes to toBeWritten() and writes...