Bound service crash with "Context.startForegroundService() did not then call Service.startForeground()" error I'm currently working on audio playback app and I'm using a started bound service to play music in background. I start and bind to the service using following code. val intent = Intent(context, MusicService::class.java) context.startService(intent) context.bindService(intent, serviceConnection, 0) It gets promoted to foreground when playing and gets demoted when music is paused. // onAudioPlay service.startForeground(NOTIFY_ID, notification) // onAudioPause service.stopForeground(false)...

Map in onDataChange [Kotlin] My code count stars (5 stars) in firebase and I have problem, if it update in realtime it counting not correct (Firebase now) = 1 = 2 = 0 = 0 = 0 And after change firebase [add 1. +=1] = 3 = 4 = 0 = 0 = 0 But if I restart app it change to normal result: = 2 = 2 = 0 = 0 = 0 Why MutableMap add map second time with new star ? class FireBaseRealTime { var listofStarsCounter : ArrayList = ArrayList(listOf(0,0,0,0,0)) var mDataBase : DatabaseReference =...

Parsing json with broken remote API Here is my model class data class Article( val id: Int? = 0, val is_local: Boolean? = false, val comments: List? = listOf()) and here is json { "id": 33, "is_local": "true", "comments": [ { "url": "aaa" }, { "url": "bbb" }, { "url": "ccc" ) ] } i am using this custom Adapter to return default value in case of parsing error like in my case is is_local field class DefaultOnDataMismatchAdapter private...

Using a socket for a custom protocol over tcp My protocol looks like this: [size: UInt16][Channel: Uint16][Protobuff packet] The problem is, it is my understanding that tcp does not guarantee that an the entire packet as sent by the user will arrive all in one. Therefore, there could technically be a situation, where I don't get the entire message at once, or even that a part of another message is sent with this message. It was quite easy, when I was just assuming that I would be getting the entire message at once, because I just read...

Android Studio Lint Checks for Kotlin Higher Order Functions I've seen the following example of a higher order function being used as a convenience method to wrap Android API version checks. fun isLollipop(func: () -> Unit) { if (VERSION.SDK_INT >= VERSION_CODES.LOLLIPOP) { func() } } However, in Android Studio 3.0 (Kotlin version 1.2.0) I'm seeing lint errors if I attempt to use an API that requires Lollipop (the minSdk for the project is 17). For example: isLollipop { appBarLayout.elevation = 4f } Lint complains about the API minimum...

IllegalStateException textview cant be null with Kotlin I am trying to create a way to update the UI when activity starts by setting the text of a TextView in the navigation drawer. I keep getting an error that the TextView cannot be null? The error I get is an illegal state Exception userEmail must not be null This is the updateUI private fun updateUI(user:FirebaseUser?) { if (user != null) { var text : String? = user.email id.userEmail.text = toString(us) val errorTriage : String? = user.email println("User Email is...

Lambda type with variable number of args in Kotlin? Is it possible to receive as an inline lambda parameter a function type which has a guaranteed return type R but a variable number of arguments? For simplicity, consider the following: inline fun Boolean?.tfn(tru:()->R, fls:()->R, nul:()->R) = if (this == null) nul() else if (this) tru() else fls() Let's assume I have other inline functions that also take lambda parameters that might be of type (A)->R or (A,B)->R or (A,B,C)->R, whose parameters I'd like to pass to this function. They...

Sealed data class in Kotlin I have the following sealed classes sealed class DownloadWallpaper : Result() { data class Progress(val hd: Boolean = false, ...) : DownloadWallpaper() data class Success(val hd: Boolean = false, ...) : DownloadWallpaper() data class Error(val hd: Boolean = false, ...) : DownloadWallpaper() } And I am trying to do the following. obs.map{ it.copy(hd = true) } Where obs is of type Observable But I cant, for two reasons since DownloadWallpaper isn't a data class. There's not...

share intent text in android studio using kotlin I want to share text in my CardView using share Intent using kotlin but there is a problem with last line in the code in kotlin the code val shareIntent = Intent() shareIntent.action = Intent.ACTION_SEND shareIntent.putExtra(Intent.EXTRA_STREAM, "ali") shareIntent.type = "text/plain" startActivity(Intent.createChooser(shareIntent, getResources().getText(R.string.send_to))) here is the problem in the code...

When should I use let {} and when just plain != null How would you write the following code in a more kotlinic way ? var returnValue = ... val s3data = presignedUrl.body() if (s3data != null) { val uploadImage = api.uploadImage(s3data.bucketUrl, s3data.awsAccessKeyId, s3data.policy, s3data.key, s3data.signature, body).execute() if (!uploadImage.isSuccessful) { crashReporterService.sendIssue("Failed uploading file", "Failed uploading file ${uploadImage.raw()}") returnValue = Result.FAILURE } else {...

kapt: how to obtain source comments? Why processingEnv.getElementUtils().getDocComment(element) always return null for any documented element coming from *.kt source?

Fast way to initialize child Kotlin class with parent class' instance properties I use Java library that defines a JSON model class named A. This class contains a lot of properties, e. g., 26 String properties named from a to z and does not have a constructor for them. I'd like to extend this class in Kotlin with a new JSON property, lateinit var aa: String (derived class will be B), and to have a fast way to create an instance of B by copying properties of existing A instance. I can serialize A and deserialize the resultant JSON to B. Are there any other fast solutions...

Annotation in Kotlin doesn't work I'm trying to convert my Android app from Java to Kotlin. For app shortcut I use shortbread library which is extremely easy to implement, but it doesn't work in Kotlin. Am I doing something wrong ? Java: @Shortcut(id = "Camera", icon = R.drawable.iconshortcut,longLabel = "Instant Scan", shortLabel = "Scan") public class CameraActivity extends AppCompatActivity { ... Kotlin : @Shortcut(id = "Camera",...

Dangling else in Kotlin I have this doubt guys, I don't know; any example to understand will be great. Does the Kotlin programming language suffer from the "dangling else" problem? If the problem is there then what is the reason in that case?

Fatal Exception: java.lang.RuntimeException with Klaxon json Kotlin Library I am using klaxon with my android app (proguard enabled) This error coming with latest android version 8.0. Any Idea what causing ? Fatal Exception: java.lang.RuntimeException Unexpected character at position 2: '< (60)' com.beust.klaxon.Parser.parse (Unknown Source:24) cc.cc.api.JsonParser$Companion.parse (Unknown Source:15) cc.cc.api.JsonParser$Companion$processResponse$1$2.onCompleted (Unknown Source:52) com.koushikdutta.async.future.SimpleFuture.getResultOrThrow (Unknown Source:10)...

Asynchronous anonymous function in Kotlin? (lambda expressions) I'm making a listview what call function when click. and I want to get function is async or sync. to block when it is async. and even i want to know how attach async mark to kotlin lambda expression. class FunctionCaller_Content(text: List, val function: List Unit)?>? = null) /* I want both of async, sync function. */ : AndroidListView_Content(text = text,...

@CreationTimestamp and @UpdateTimestamp don't work in Kotlin This is my Tag and Post Entity classes: @Entity class Tag( @get:NotBlank @Column(unique = true) val name: String = "", val description: String = "" ) { @Id @GeneratedValue(strategy = GenerationType.SEQUENCE) val id: Int? = null @ManyToMany(mappedBy = "tags") val posts: MutableSet = mutableSetOf() @CreationTimestamp lateinit var createDate: Date @UpdateTimestamp lateinit var updateDate: Date fun addPost(post: Post)...

Android Studio crashing every time I run a JUnit test I run this test: val type = object : TypeToken() {}.type ApiHelper.request(type, "-- --- ---").subscribe({}, { Assert.assertTrue("Invalid http url is valud", (it.message == null || it.message!!.contains("invalid url:") == false)) }) And Android Studio literally crashes every time I run it. The request() method returns a RxKotlin Single but I am testcompiling RxKotlin. However, even if I comment out the code and run an empty test Android Studio still crashes....

How to use SQLite in Kotlin/Native? For a multi-platform project, I consider Kotlin/Native, with the hope to have a common code base at least for business logic and saving of data. For saving of data I would like to use a database like SQLite. However, according to another stackoverflow thread, if I want to compile to Kotlin/Native, I cannot...

RxJava reconnection on connectable observable does not work Hi, guys. I'm trying to make some kind of MVC with RxJava. So the idea is to make some constant subscriptions that will be always subscribed to some observable. Also this observable can be restarted at any time to rerun, for example a network call. I tried this code to test this feature: class Main { companion object { @JvmStatic fun main(args: Array) { val obs = Observable.interval(1, TimeUnit.SECONDS, Schedulers.io()) .publish()...

Kotlin properties cannot be overridden with subinterface In the following stripped down example, can you explain why the Kotlin compiler complains when overriding a that we restrict its type further(compiler message: Var-property type is 'B', which is not a type of overriden public abstract var a: A) interface A interface B : A { fun someFunc():Boolean } class C : B { override fun someFunc(): Boolean { return true } } abstract class D { abstract var a: A } class E : D() { override var a : B = C() fun...

Kotlin lambdas without using objects I am trying to convert from java to kotlin. The current java interface is something like this: interface MyInterface { void foo(int x, int y); } MyInterface testing = (int a, int b) -> System.out.print("TESTING"); My current kotlin conversion is: interface MyInterface { fun foo(x:Int, y:Int) } val kotlinConversion = object: MyInterface { override fun foo(x: Int, y: Int) { println("TESTING") } } Is there a way to write the variable kotlinConversion such that it...

Is there a REAL advantage to using Kotlin over Java [on hold] It seems that there is a bit of a push to get Android developers to start using Kotlin. This Kotlin site shows some of the differences but I'm a bit skeptical. For example, they claim that Java doesn't provide Singletons and Kotlin does, but anyone can easily create a Singleton class with little effort in Java. I'm a fairly new Android developer and I'm very comfortable with Java. I was...

Recycler View drag and drop across different view types I have implemented drag and drop for recycler view with the default android ItemTouchHelper like the following implementation. https://github.com/iPaulPro/Android-ItemTouchHelper-Demo My callback class looks as follows. class ItemTouchHelperCallback(private val mAdapter: ItemTouchHelperAdapter) : ItemTouchHelper.Callback() { override fun isLongPressDragEnabled(): Boolean = true...

Kotlin, Android Generic Response handler error and validate response using retrofit,rxjava and dagger I'm trying to create generic architecture to consume complex json structure as follows: Json Format { "type": "success", "code": "s-groups-0006", "description": "Index List successfully", "result": { "asOnDate": 1505457095278, "indexList": [ { "change": "22.35", "changePercent": "0.27", "isDefault": true, "isEditable": false } ] } } Dagger Format @Singleton fun provideGson(): Gson = GsonBuilder()...

I am now developing an Android app with Kotlin,but it occurred an error:CompilationException: Couldn't inline method call 'readText' into I'm now studying kotlin,but when I tried to use it for network request,the AndroidStudio threw an exception below with my code. public class CustomRequest(val city_code:String){ fun execute():ForecastResult{ val url = URL(SERVER+PARAM) val forecastResStr = url.readText() Log.e("MyApplication",forecastResStr) return JSON.parseObject(forecastResStr,ForecastResult::class.java) } } Now I can't Compile with my app,please help.Thanks. the exception is...

arrayOf() , listOf() sealed class's objects mysteriously becoming null There is a sealed class : sealed class Alphabet(val name: String) { object A : Alphabet("A") object B : Alphabet("B") object C : Alphabet("C") object D : Alphabet("D") object E : Alphabet("E") companion object { val array = arrayOf(A, B, C, D, E) val list = listOf(A, B, C, D, E) } override fun toString(): String { return name } } And there is another class with companion object : class AlphabetMap { companion object { val map = mapOf(...

Kotlin - Transform value at initialisation i'm new in kotlin and i want to know if we can transform a content value at initialisation : with this example : @Document data class Category( @Id val id: Id? = null, val label: String ) Category is a document (entity for mongodb) and when i'm instanciating this object, i want to transform label property in uppercase. How can i do that to stay idiomatic with the language ? The point is to keep the immutable properties of the val keyword. val categ = Category(label = "Test")...

Is it possible using String as PrimaryKey in Android Room I use uuid in my java backend server. So I need to use that uuid in room android to make sure entities are sync'd properly. I am aware of Is it possible to apply primary key on the text fields in android database and text as primarykey in android. I want to create something...

Unwanted selections in RecyclerView In my app I have a RecyclerView which contains 15 static items consisting of a TextView and a CheckBox: On click on the item, the according checkbox is set to checked and the item is added to a selection-list. The problem: When I scroll down and select an item, scroll up again I alwys see another checkbox checked. While debugging I noticed, that only my actually selected item has been added to the list, but nethertheless its a bad user experience when other items are checked/"selected"...