Idiomatic Kotlin for Level Order Traversal of BST Following is my implementation of Level Order Traversal of a BST: fun levelOrder(): Iterable { class InternalNode(val node: Node, val level: Int) val yetToVisit = emptyQueue() val visited = emptyQueue() root?.also { yetToVisit.enqueue(InternalNode(it, 1)) } while (!yetToVisit.isEmpty) { do { val node = yetToVisit.dequeue().also { visited.enqueue(it.node.key to it.level) } listOf(node.node.left, node.node.right)...

Kotlin, operations with Float produces wrong result Here is my code: var holdings=0.011f Log.e("holdings", "$holdings") holdings=holdings-0.01f Log.e("holdings", "$holdings") Expected results: holdings: 0.011 holdings: 0.001 Actual results: holdings: 0.011 holdings: 0.0010000002 What am I doing wrong? Is there some special course I need to take to subtract a float from another?

Class is not abstract and does not implement abstract base class member I'm confused by this Kotlin error associated with providing an implementation for an abstract class that has been imported from a maven package. I have a maven library that is written in Kotlin and exposes an abstract class called APIGatewayRequestHandler. In my app that imports the library, I provide an implementation of the abstract class: class GetWelcomeMessageHandler : APIGatewayRequestHandler() fun handleAPIGatewayRequest(input:...

Kotlin Comparator Compilation Error in IntelliJ Using Kotlin 1.2.41-release and given a List, the following code generates a compilation error in Intellij, although Gradle command line build works. sortedWith(compareBy({ it.first }, { it.second })) Cannot choose among the following candidates without completing type inference. public fun compareBy(vararg selectors: (???) -> Comparable?): kotlin.Comparator defined in kotlin.comparisons public fun compareBy(vararg selectors: (Pair) -> Comparable?): kotlin.Comparator defined in...

Any open source Android library for handling PDF and getting selection/highlight words? I thought about a use case where you would like to highlight something from the PDF, then depending on the highlighted words you can trigger something. I'm looking for a library that can do this.

Phone is not going to sleep mode when specific activity visible I am using webview when activity first time open then it work fine and phone go to sleep mode after time that provide in settings then i press home button and after that again open app from recent app at this time phone is not going to sleep mode. Thanks

WebView is failing to load some webpages I getting the below error when trying to load some webpages Error parsing a meta element's content: ';' is not a valid key-value pair separator. Please use ',' instead. How do I solve it?

send different types of post parameters in api in kotlin I'm a new kotlin dev .I try to send different types of post parameters in api but it did not work correctly.Any idea why? here is my code. Firstly I wrap my parameters in a simple container and pass that as a parameter to AsyncTask, like this: class MyParams{ var paramName: String = "" var paramaddress: String = "" var paramlatitude: Float = 0.toFloat() var paramlongitude: Float = 0.toFloat() constructor(funName: String, funAddress: String,...

A field not declared optional accepted null as the value I have a data class data class Bean { var value: String = "" } I got a Json from server: { "value":null } What I expect is since value is not optional, so the null cannot be assigned and value will remain as "". But using the debugger I found that value is null, and therefore some method I called on it throws the below exception: fun matches(stringToMatch: String): Boolean { return this.value.toLowerCase() == stringToMatch.toLowerCase() } kotlin.TypeCastException: null...

Java 8 Interface with default Methods not working when Jacoco Enabled We are having an interface with default methods and we implemented that interface in both Java and Kotlin classes and we provided the implementation for the non default methods. When we run in debug mode (which doesn't have testCoverageEnabled = true) and the app works as expected. But when we run in different config with testCoverageEnabled = true, the app is crashing with below error java.lang.NoSuchMethodError: No static method $$triggerInterfaceInit()V in class...

Kotlin custom Dialog I am new to kotlin, On my application I want to create a custom dialog. I want to show a common dialog. when I call my Dialog, InfoMessageDialog(activity, "Test Title", "Test desctiption of the dialog.").show(); I am getting an error like, FATAL EXCEPTION: main Process: com.bmates.testApp, PID: 4350 java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter savedInstanceState at...

Kotlin - why do I get a KotlinNullPointerException Consider the following code: Example fun main(args: Array) { maybeWriteMessage() } fun maybeWriteMessage(message: String? = null) { writeMessage(message!!) } fun writeMessage(message: String) { println("Hello World") } Output Exception in thread "main" kotlin.KotlinNullPointerException at com.series0ne.ApplicationKt.maybeWriteMessage(Application.kt:8) at com.series0ne.ApplicationKt.maybeWriteMessage$default(Application.kt:7) at...

To send another fragmented data after the "onActivityResult" function I'm developing a restaurant program. I'm having a problem. Now I will tell you the events that happen during product selection *The application consists of two fragments. Activity name is 'MasaDetay'. FragmentOne name is 'MasaUrunler', FragmentTwo name is 'MasaAdisyon' * Actions in the 'MasaUrunler' fragment I bring the products from the database with Volley and I list them on the screen thanks to a RecycleView I print the listed products and I choose the quantity, portion and...

Kotlin swipe with ItemTouchHelper left click dont work Looking at recyclerviews designs I saw the swipe of this post and decided to try the left and rigth swipe works perfectly showing the buttons and the onclick of the button in the right panel works but when i click de button in the left panel nothing happens. Class for swipe abstract class SwipeHelperContratos(context: Context, private val recyclerView: RecyclerView) :...

BigQuery, how to define array like field programmatically? I'm trying to start a datawarehouse project, this is what I would like my schema to look like: table: event_log schema: -> info -> user_id: "xyz" -> user_properties // 0 -> key: "name -> value -> int_value: null -> string_value: "osp" ... -> 1 // and it goes on The problem is I don't know how to programatically define this array like structure. I took the idea from here: <a...

Split directory from string in Kotlin I guys, I'm trying to split the directory of string like this: val pwd = "travel/holiday/" val listOfDirectory = pwd.split("/".toRegex()) output: "travel","holiday","" Why is created a blank space in the last position? Also, How can I remove that?

When adding activity stack from notifications, make sure root activity is always in the stack without duplication Im starting a new activity from a notification however I cant seem to achieve the behaviour Im looking for. I want to start an activity, lets call it B. If the app is currently not running I want to add a parent activity A to the stack first then B, so that when you press back from B it goes to the parent A. A is a home activity. (Most right is the top of the stack) A -> B However if the app is currently running and it has a stack of activities, lets say like this: A -> C I don't want...

When running google arcore example hellosceneform I get an error ErrorCause org.jetbrains.kotlin.annotation.plugin.ide.AnnotationBasedPluginModelBuilderService and Gradle project sync failed

SimpleXML Kotlin - array of elements Hi all. I've got an XML: NewQuoteAPI.xml tratata.xml and want to parse it to List. So I have this classes: @Root (name="files") data class WSDFileDAO(@field:Element (name="file") var file : String) { constructor() : this("") } @Root (name="WSDConfig") data class WSDConfigDAO(@field:ElementList (name="files", inline=true, required=false) var files : List) { constructor() : this(mutableListOf()) } Persister().read(WSDConfigDAO::class.java,...

Kotlin - how to get rid of this compiler error? I have this class data class Properties( val actionBarColor : Int , val fileName : String) : Serializable{ var title : String = "" var readModeOnly : Boolean = false } and this if condition var properties = Properties() if(properties?.readModeOnly){ } But the compiler says , required Boolean found Boolean? . What should i do to make this work? I don't want it to be nullable.

Simplifying return from multiple nested blocks in Kotlin The code in question is as: fun get(context: Context, s: String): MyObjectDb? { return context.database.use { return@use select(MyObjectDb.TABLE_NAME, *MyObjectDb.PROJECTION) .whereArgs("${MyObjectDb.COLUMN_S} = {s}", "s" to s) .exec { return@exec getOne(MyObjectDb::fromCursor) } } } When I check this for code style (sonar with Kotlin plugin that uses detekt) I get a warning that...

how to create kotlin class when developing intellij idea plugin? When developing Intellij Idea plugin creating java classes can be done with JavaDirectoryService which creates PsiClasses according to file templates. Is there any way to create kotlin classes with similar method?

Create observable for each item in list and combine their results I have the following two Single functions: fun getStrings(): Single { return Single.just(listOf("a", "a.b", "a.b.c")) } fun getStringParts(s: String): Single { return Single.just(s.split(".")) } I want to combine them in a way that results in a Map

Deserialize a Firebase Data-Snapshot to a Kotlin data class Hi I have a Kotlin data class as follows data class User ( @get:Exclude val gUser: Boolean, @get:Exclude val uid: String, @get:PropertyName("display_name") val displayName: String, @get:PropertyName("email") val email: String, @get:PropertyName("account_picture_url") val accountPicUrl: String, @get:PropertyName("provider") val provider: String ) I am able to serialize the object without an issues. But i'm having trouble deserializing the...

Spring WebConfig Filter I've got my web configuration like this @Configuration @EnableWebSecurity class WebSecurityConfiguration : WebSecurityConfigurerAdapter() { @Inject lateinit var env: Environment @Bean fun authTokenFilter() = AuthTokenFilter(env) override fun configure(http: HttpSecurity?) { http ?.csrf()?.disable() ?.exceptionHandling()?.authenticationEntryPoint({ _, response, _ -> response.sendError(HttpServletResponse.SC_UNAUTHORIZED)...

Kotlin write file in internal storage in my project I have my main activity with a BottomNavigationView with 2 sections. When I leave my default section and I switch to the other one, I create a long string and I need to save it as a file in the Internal memory of the device. I experience an issue though: I get this error at compiling time: “can handle thread in that has not called looper.prepare()” How could I solve this issue and save my file? Do I need a separate activity? Unfortunately I have not experience in handling...

Start activity from activity or view holder New to Android development here. I am creating a RecyclerView that presents a new activity when certain items are clicked. I searched online and all of them would define a click listener interface, pass the listener to view holders, and ultimately call startActivity from the main activity. Alternatively, I came up with the following approach. What's wrong with it? It is just a few lines of code in the adapter class and seems to work equally well override fun onBindViewHolder(holder:...

Array of images to store in cache? I am working with the cards (cardView) and trying to store the images inside the array (array to string; store that in cache and when required unpack back to array). My question is: what is the most convenient way to store the images in an array? Store the bitmaps (bitmapToString etc)? Turn the bitmaps (I get the images from the gallery and camera) into URIs? Absolute paths? The number of...

How to modify FragmentAdapter list inside Fragment I'm trying to replace fragment with another fragment when button is pressed. I have made a list where I add fragments that I want to be loaded on start. The problem is that I have made a function inside FragmentStatePagerAdapter: private val list: MutableList = ArrayList() override fun getItem(position: Int): Fragment { return list[position] } override fun getCount(): Int { return list.size } fun addFragment(fragment: Fragment){ list.add(fragment) } fun...

Android: Custom font works for TextView, not for Button I cannot get a Button to use my custom font. It works fine with a TextView, not with a Button (which is a subclass of TextView). I am using Android Studio 3.1.2 with minSdkVersion 26 and Kotlin. res/font/font.xml res/layout/fragment.xml ... ... The above works. Replace TextView with Button and it stops working.