Kotlin actor to actor communication An actor can be sent a message with actor.send() or actor.offer() Once my actor gets the message from its channel I'd like to return a response. How do I do this? I don't see any obvious built in method.

Creating an Android Studio with Kotlin App that features a database with large amounts of information I am new to programming and databases. What I am looking to create is an android app using android studio with kotlin. The app has a simple search function where users can search a database that contains a large amount of information. The information would contain documents, rules, regulations, legislation mainly from various sources. I would like to import this information into a database so users can search this information centrally. The issue is, and where I am looking for guidance is...

When not to use Koltin sequences It seems like turning a list into a sequence before performing operations on it is more efficient. In that case, when would one want to not use a sequence?

when to use lateinit, init block, and companion object. Kotlin I am working on the android Bluetooth chat project from the developer site and i am trying to use Kotlin instead of java. i am new to Kotlin and i am just having some confusion about the "right" way to use my init block and lateinit keyword along with my companion objects. in the code that i am posting i do not have a companion object but i am wondering if i should. so far i mainly just use a companion object as a way to sort of imitate java's static class members, or to sometimes contain...

Kotlin error with Gradle 3.0.0 After upgrading to Android Studio 3 and gradle 3.0.0 errors appeared: http://joxi.ru/eAOqoLwfxgKqRm Version kotlin - 1.1.51 Version Gradle - 3.0.0 How can this be solved? Thanks!

Reversing an infix boolean result kotlin I have an infix function, let's say it's this one: class test{ infix fun equalsTen(value:Int):Boolean = value.equals(10) } Obviously this isn't the real function, just an example. Additionally Lets say that I have this function: fun doSomething(value: Int){ val testClazz = test() if(testClazz equalsTen value){//line 3 //do something } } How can I reverse the condition in line 3? Right now it's basically: if(testClazz.equalsTen(value)){...} How can I change it...

Android Studio installation issue So I just reinstalled Windows 10 and Android Studio and I've got some issues.. <a href="https://i.stack.imgur.com/wEHDo.png" rel="nofollow noreferrer">And I can't get it what's...

Kotlin - Is here a smart way to throw NotImplementedError for all the methods of a class? I need to implement an interface (ResultSet) having hundreds of methods. For now, I'm going to implement only a subset of these methods, throwing a NotImplementedError for the others. In Java I found two solutions: Create an abstract class AbstractResultSet implementing ResultSet, declaring all methods to throw NotImplementedError. No hacks, but a lot of boilerplate code. Use Proxy.newProxyInstance to implement all methods together in the InvocationHandler. Less code but also less...

Kotlin wrapper for React-Native Since KotlinJs has been released is some interesting projects you may find on the net like this and this, but it also could be nice to see KotlinJs wrappers for React Native framework. I personally don't like JavaScript for many reasons and would like to see samples on Kotlin to try...

How to use &amp;quot;setTextColor(hexaValue)&amp;quot; on Kotlin for Android, Background In Java, I could directly change the text color of a TextView, using the standard hexa-decimal value of it: textView.setTextColor(0xffffffff); //white textView.setTextColor(0x00000000); //transparent textView.setTextColor(0xff000000); //black textView.setTextColor(0xff0000ff); //blue //etc... Very easy... The problem On Kotlin, if I try to write such a thing, I get with a weird build error: Error:(15, 18) None of the following functions can be called...

zip function return an empty result i am using Rxjava with my app so i can fetching my data from tow different API server , to combine the result using "zip" function and here is my code : class1:- var service = retrofit(1).create(cc::class.java) var service1 = retrofit(0).create(cc::class.java) var obs: io.reactivex.Observable = service.getsky() .subscribeOn(Schedulers.newThread()) .observeOn(AndroidSchedulers.mainThread()) var result2: io.reactivex.Observable = service1.getTrends()...

Why aren't the entries in a Kotlin Pair mutable? I have a MutableList of Pairs and I'd like to decrement the value of the first entry so my condition my pass(change): while(n > 0) { if(sibice[i].first > 0) { sum += sibice[i].second //sibice[i].first-- will not compile n-- } else i++ } But the Pair class doesn't let me do that, besides creating my own pair is there any other workaround and why is this even the case?

Room Peristence Library and enigmatic error I try to use Room in Android Studio 3.0 with kotlin. I have successfully created 3 entities that work well (database is created, i can insert rows and so on). Now, i want to add some functionnalities but i have this enigmatic error: Warning⚠️ Supported source version 'RELEASE_7' from annotation processor 'android.arch.persistence.room.RoomProcessor' less than -source '1.8' Error:Execution failed for task 'appkaptDebugKotlin'. > Internal compiler error. See log for more details...

duplicate entry: META-INF/myLibrary.kotlin_module After updating to Android 3.0, getting Kotlin error: Execution failed for task 'myLibrarytransformClassesAndResourcesWithPrepareIntermediateJarsForDebug'.

java.lang.RuntimeException: java.util.zip.ZipException: duplicate entry: META-INF/myLibrary.kotlin_module

This is my library buid.gradle file: apply plugin: 'com.android.library' apply plugin: 'kotlin-android' apply plugin: 'kotlin-android-extensions' ... dependencies { api...

How to get current local date and time in Kotlin How to get current Date (day month and year) and time (hour, minutes and seconds) all in local time in Kotlin? I tried through LocalDateTime.now() but it is giving me an error saying Call requires API Level 26 (curr min is 21). How could I get time and date in Kotlin?

Android kotlin : unable to read class file EDIT : this was much simplier than I thought, I just needed to clean the project ! I'm trying to define an interface inside a fragment containing a GridView to force any activity that would attach the fragment to implement that interface and the onImageSelected method. For it once I check if the activity correctly implements the Interface, I cast it onto a callback object. class MasterListFragment : Fragment(){ lateinit var mCallBack: OnImageClickListener interface OnImageClickListener{...

Android ValueAnimator increase only height Using my below code scale increases the height both ways. i want to increase the height to one direction private fun scaleView(view: View, newHeight: Int) { val animation : ValueAnimator = ValueAnimator.ofInt(view.measuredHeight, newHeight); animation.addUpdateListener(object: ValueAnimator.AnimatorUpdateListener { override fun onAnimationUpdate(valueAnimator: ValueAnimator?) { val animatedValue = valueAnimator!!.animatedValue val layoutParams:...

Gradle sync failed: Could not GET 'https://jcenter.bintray.com/org/jetbrains/kotlin/kotlin-gradle-plugin/1.1.3-2/kotlin-gradle-plugin-1.1.3-2.pom' Recently, I update the code from my team, I find they have been using Kotlin. However, I can't run my project now. Below is the detail logs: Could not resolve all dependencies for configuration ':classpath'. Could not resolve org.jetbrains.kotlinkotlin gradle plugin1.1.3-2. Required by: project : Could not resolve org.jetbrains.kotlinkotlin gradle plugin1.1.3-2. Could not get resource '<a...

How to use Kotlin Coroutines? Hello guys and sorry for the inconvenience. I'm a completely noob in 'android development' but I try to learn as much as I can. I've created a simple app using Kotlin and a tail recursive function that calculates the factorial of a BigInteger. The app works great but when I try values larger than 10000 the app crashes. I want to use Kotlin Async and Await to be able to achieve my goal. Can you please help me? Here is the code: package com.example.paciu.factorial import...

Cannot zip Rxjava Observables I am using RxJava 2.* and I want to merge the results of two observables (one from retrofit and another from room) by using zip operator(feel free to suggest better). Model objects that come from remote server are different from the one coming out of Room Database. I want to map the objects from Remote into that of local Merge those two results Display the result. My remote API looks like this : interface CategoryService{ @GET("categories") fun getCategories(): Observable } And my...

Retrofit: Getting an empty body on response retrofit I am getting an empty body on response retrofit. This is what I get from my logs: V/test: Response{protocol=http/1.1, code=200, message=, url= This is my code: val call: Call = service.getTestCase() call.enqueue(object:Callback { override fun onResponse(call:Call, response:Response) { if (response.isSuccessful()) { // tasks available Log.v("Test",response.body().toString()) Log.v("test",...

Firebase-Firestore not loading 2 documents' information simultaneously Good morning So, I am able to load information from my firebase documents and collections, to a certain extent... When my collections have 1 Document, everything goes smoothly. When it has more than 1 Document, well, the app breaks. So, I have this: db.collection("KitListCategorie").get().addOnSuccessListener { snapshot -> for (document1 in snapshot.documents) { val data1 = document1.data val weights = data1["categoryName"] as String val misc =...

How to work with foldRight() in Kotlin? I try this code println(listOf(1, 2, 4).foldRight(0) { total, next -> total - next }) I thought it works like 0 + 4 - 2 - 1 = 1. But it returns 3. Why? Sorry for this silly question.

Can you map/reduce a String into an Int? I was solving a problem on codeforces in which I had to sum up the digits of a big number (it can have up to 100k digits) and I'd have to repeat that process until there is only one digit left and count the number of times I did that and I came up with a working solution, however I'd like to know if some things could have been done in a more "Kotlin-ish like way", so given: fun main(args: Array) { println(transform(readLine()!!)) } fun transform(n: String): Int { var count = 0...

Only safe or non null assserted calls are allowed on a nullable receiver type of arraylist Just started using kotlin for android development.My arraylist is declared like this- var day1: ArrayList? = null Now I am trying to access an element by its position val dietPlan= day1[position] but i am getting below compile time error- Only safe or non null assserted calls are allowed on a nullable receiver type of arraylist Why am i getting this error and how can i resolve it?

Auto increment list items to Firestore Document Morning everyone, So I have a List that I can populate with items from a spinner and it works. I can create multiple vars (for each item that is added to the list) and add them to a firestore document. Although, this is not optimal since I don't know how many items the user will select to add. I tried this ` createListBtn.setOnClickListener { var item: String = "item" var i:Int = 1 var newItem: String = "item" + (Integer.parseInt(item.substring(1,item.length))+1)...

Only Last Element added to RecyclerView in Android (Kotlin) I am passing a list of 7 items to the recyclerview and it is only binding the last one. Through the use of logging I cal see that the getItemCount() is returning 7, but the onBindViewHolder is only being called once. I do know (again through logging) that the list that I pass to the adapter is the complete list. Could you please help me find out why only the last element is displayed and not the whole list. Thank you. Activity code: class HabitActivity : AppCompatActivity() { var...

Kotlin cannot access protected abstract method I have the following classes structure: abstract class Abstr{ protected abstract fun m() } class Child : Abstr(){ private val subChild: Abstr = Child() override fun m() = subChild.m()// Error:(12, 18) Kotlin: Cannot access 'm': it is protected in 'Abstr' } I got an exception Kotlin: Cannot access 'm': it is protected in 'Abstr' It little bit confusing, because the same structure is legal for java. According to <a...

kotlin work with Resources (array and function parameter) I need to define array of RAW Resources by using kotlin for example var x = ArrayList x.add(R.raw.cat) and the other question is to pass resource to function fun myFun(res:Resources ){ mp=MediaPlayer() mp.start(res) } I will be very thanksfull for help

@StringRes, @DrawableRes, @LayoutRes and so on android annotations lint check with kotlin parameters assuming you have such data class with default parameters data class Info( @DrawableRes val iconRes: Int = 0, @StringRes val stringRes: Int = 0, @LayoutRes val layoutRes: Int = 0) so you can create this data-class like val data = Info( iconRes = R.drawable.icon, stringRes = R.string.text, layoutRes = R.layout.layout) in this case there isn't any lint error But when i try to use default parameters a lint error...