Passing array of Parcelable using Intent.putExtra I have created a Parcelable class called Song and am trying to pass an array of them between activities using Intent.putExtra() currently once i get to the activity and use this.intent.getParcelableArrayExtra i get an array of parcelable and I cant find a way to convert it back to an array of Songs. code starting activity: val i = Intent(this, CompletedSongsActivity::class.java) val completedSongs = songList.filter{ it.solved }.toTypedArray() i.putExtra("COMPLETED_SONGS", completedSongs)...

Will Kotlin's mapTo() overwrite data already in the Array? I am trying to map the users from my database to an ArrayList of just their usernames, with the catch being that I need the first entry in the array to be empty, as the array of strings is going into a Spinner's array adapter. So if I had code like this: val users = ArrayList() users[0] = "" dh.getUsers().mapTo(users) { it.toString() } So will users still have "" in the 0-th position, or will the mapTo overwrite it?

About Kotlin and functions So Ive started learning Kotlin and I have a question about functions. In Kotlin you can do the javascript thing of creating a variable that can hold any type. But functions need to have their parameters typed. So is the practice in Kotlin to type all variables anyway? Is it not kind of pointless allowing the variables to be untyped but forcing types for the parameters and return values of functions?

How to find out is an array is empty? I have boolean flag and I have to func (fun animation and fun reAninimation - it is transition between two drawables. This is the transition between the two drawings Idea of this class is I have two side of coins. I added it in an array. If array is empty, i call only animation, if it not empty i call firstly reAnimation and then animation my array: var arrayShape: Array? = null it is a part of the OnCreate method. override OnCreate() ... if(isArrayEmpty(arrayShape!!))...

Circumvent observable delegate Is it possible to circumvent the observable delegate in certain cases? Use case: val ls: ArrayList by Delegates.observable(arrayListOf()) { _, _, new -> if (someCondition) { usesList(new) // I want to reset ls to arrayListOf(), but without the invocation of the observable delegate. } }

Asynchronous SSE How can I asynchronously make and handle SSE events? Optimally, I would like to be able to do something like this Request request = new Request("http://someendpoint") request.onMessage(payload -> System.out.println(payload)) request.onError(error -> error.printStackTrace()) request.onClose(() -> System.out.println("closed")) request.onConnect(isReconnect -> System.out.println("connected")) Obviously doesn't have to be exactly like that, just thought it would help explain what I was trying...

Position of `@` label in Kotlin when denoting receiver with `this` I am a newbie in Kotlin. I am curious about the difference of labeled this in Kotlin with prefix @ or postfix @. I have just seen a code which writes SignInActivity@this, which seems to work exactly same as this@SignInActivity. Are these two exactly the same thing? If not, what is the difference between the two? I was trying to do some research on *@this form, but I couldn't find any reference on it. All I could find was <a href="https://kotlinlang.org/docs/reference/this-expressions.html"...

Android - IllegalStateException : cursor.getString(idx) must not be null I have follow all the stuffs here, but Why does cursor.getString(idx) said it must not be null? I supply all the necessary params.. here's my getfilepath: fun getFilePathFromUri(context: Context, imageURI: Uri): String? { var cursor : Cursor? = null var result: String try { val projection = arrayOf(MediaStore.Images.Media.DATA) cursor = context.contentResolver.query(imageURI, projection, null, null, null) if (cursor == null) {...

Why nullable numbers are not preserve identity In kotlin nullable values are not preserving identity but equality, val a: Int = 10000 val boxedA: Int? = a val anotherBoxedA: Int? = a print(boxedA === anotherBoxedA) // !!!Prints 'false'!!! print(boxedA == anotherBoxedA) // Prints 'true' I just wanted to know why is this different ?

Companion objects benefits of posibility to implement interfaces Why in Kotlin/Scala companion objects can implements some interfaces, what benefits this can have? When is useful to use this feature?

Custom Glide ModelLoader for base64 images I have images from some SOAP API that are encoded in base64. To load them directly with Glide I decided to wrote custom ModelLoader. Glide Version: 4.3.1 Glide load line: GlideApp.with(activity) .load(Data().apply { code = licensePlateData.licensePlateImgId }) .into(view.imageLicense) GlideModule: @GlideModule class MyAppGlideModule : AppGlideModule() { override fun registerComponents(context: Context, glide: Glide, registry: Registry) {...

Return internal class calling object function I'm testing with Kotlin and I'm writing a small library to be imported and used by a test App project. In the library project I marked my classes as internal because I don't want them to be visible for the App project, but I would like to have a single entry point for the library, and for that I am using a Kotlin object like shown below LIBRARY object Library { fun getComponent() = AwesomeComponent() } internal class AwesomeComponent() { // some implementation } TEST APP class...

Kotlin: Fetching data from Firebase I'm struggling to find an efficient way to fetch individual values from my Firebase Database. I'm coming from working with Swift. When using Swift to fetch data from Firebase, it was as simple as creating a dictionary and accessing the data through that and that allowed me to have access to that one value to do something with it. E.g guard let dictionary = snapshot.value as? [String: AnyObject] else { return } let username = dictionary["username"] as? String if username == "Bob" { // do...

How do I convert an array of Strings to an Array of Int in Kotlin I am looking to convert an List to an List in Kotlin. val stringArray = "1 2 3 4 5 6".split(" ") val intArray = MutableList(0, {0}) for (item in stringArray) { intArray.add(item.toInt()) } The above will do it, but it feels as if there is a better way of doing this (possible with lambdas and streams?).

Android room typeconverter issue I'm try to using save values to database via room persistance library. My SettingsValueModelConverter is wrong somethings are missing. How I can save SettingsKeyContract objects best way? Logcat: SettingsModel Error:(14, 1) error: Cannot figure out how to save this field into database. You can consider adding a type converter for it. Codes: object SETTING_CONS{ const val TABLE = "Content_Setting" const val ID = "uid" const val KEY = "key" const val VALUE = "value"...

How to create hql query with left join using field from extending object I have this class called Locatable: @Entity @Table(name = "locatable") @PrimaryKeyJoinColumn(name = "device_id", referencedColumnName = "id") open class Locatable: Device() { @Basic @Column(name = NAME_COLUMN) var name: String? = null } as you can see Locatable extended Device, Device looks like this: @Entity @Table(name = "device") @Inheritance(strategy = InheritanceType.JOINED) abstract class Device { @Id @GeneratedValue(strategy = GenerationType.SEQUENCE, generator =...

IncompatibleClassChangeError: Class 'java.lang.VirtualMachineError' does not implement interface 'java.lang.CharSequence' I am having weird problems with my code and i cannot explain anything that's happening. It's crashing on Marshmellow but not on Nougat which makes this more bizarre. I can point to a line where the error occurs but the error itself is not clear. I am not sure what is crashing and how to prevent it. Here are the details: The crash happens when i try to make a call to the server. To do this, i use Retrofit alongside RxJava and i do this in Kotlin. Here is my code: fun login(username: String,...

kotlin delegate property ,In a get() method how i can access the value? Kotlin has delegated properties which is a very nice feature. But I am figuring out how to get and set the values. Let's say I want to get value of the property which is delegated. In a get() method how i can access the value? Here's an example of how I have implemented: class Example() { var p: String by DelegateExample() } class DelegateExample { operator fun getValue(thisRef: Any?, property: KProperty): String { return "${property.name} " } operator fun...

Firebase sign in failed on android app my app is showing error on signin failed on firebase.. in log it says - com,google.firebase.auth not found . what to do ? i have enabled email/password login in firebase console here is my code. public override fun onStart() { super.onStart() // Check auth on Activity start if (mAuth!!.currentUser != null) { onAuthSuccess(mAuth!!.currentUser) } } private fun signIn() { Log.d(TAG, "signIn") if (!validateForm()) { return }...

Kotlin Coroutines with timeout I'm currently writing a test-function which should run a block or (when a certain timeout is reached) throws an exception. I was trying this with Coroutines in Kotlin but ended up with a mixture of Coroutines and CompletableFuture: fun runBlockWithTimeout(maxTimeout: Long, block: () -> T ): T { val future = CompletableFuture() // runs the coroutine launch { block() } return future.get(maxTimeout, TimeUnit.MILLISECONDS) } This works, but I'm not sure if this is the...

Type inference with lazy initialization and generic factory method in Kotlin I have a factory method that produces some list of : inline fun getObject(fileName: String): List The factory method should be used for lazy initialization like this: val points: List by lazy { ObjectFactory.getObject(pointsFileName) } Now the Kotlin compiler obviously has not enough type information inside the lambda and complains: Type inference failed: Not enough information to infer parameter T in inline fun getObject(fileName: String): List Please specify it explicitly....

How to create HQL query using fields from extended class I have those both classes: Locatable and Device such that Locatable Extends Device: Locatable: @Entity @Table(name = Locatable.TABLE_NAME) @PrimaryKeyJoinColumn(name = "device_id", referencedColumnName = "id") open class Locatable: Device() { @Basic @Column(name = NAME_COLUMN) var name: String? = null } Device: @Entity @Table(name = Device.TABLE_NAME) @Inheritance(strategy = InheritanceType.JOINED) abstract class Device { @Id @GeneratedValue(strategy = GenerationType.SEQUENCE,...

Calling method in generic class through reflection I am attempting to setup a function taking in a generic class that in turn calls a method within that class through reflection. Below code compiles, however when I run it I get this error: java.lang.IllegalArgumentException: Callable expects 2 arguments, but 1 were provided. Why does Kotlin claim there should be 2 arguments, when the method only takes one? What should the arguments be? class myClass { fun setData(data: List) { //Do stuff } } fun ProcessStuff( @Autowired d : T,...

Data Binding: ObservableField with lambda value doesn't compile I'm trying to define the visibility of the View by calculating the lambda that takes one parameter as an argument. I'm using Kotlin, btw. In my ViewModel I have: val customerPropVisibility: ObservableField Int> = ObservableField( { _ -> // body of the lambda }) The binding expression for the View is the following: android:visibility="@{vm.customerPropVisibility.invoke(title)}" vm and title are properly declared as variables in the data tag of the...

Kotlin lazy var throwing ClassCastException: kotlin.UNINITIALIZED_VALUE I've reached the hair pulling out stage with this one! I have a lazy var declared in a Kotlin data class. It is a Boolean and calculates it's value based on other fields in the class. The way that the Lazy.kt implementation works is to creat an anonymous object called UNINITIALIZED_VALUE to use as the basis of determining whether or not the lazy var has been initialized. Each lazy var instance will have its own unique instance of UNINITIALIZED_VALUE. This object is stored in the _value...

Multiple Permission at once not working in android I am trying to get 2 permission at once but unable to do so. I have done this before but it is just not working now. if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) { if (ContextCompat.checkSelfPermission(context, Manifest.permission.READ_CONTACTS) != PackageManager.PERMISSION_GRANTED) { ActivityCompat.requestPermissions(context, Array(2) { Manifest.permission.READ_CONTACTS ; Manifest.permission.WRITE_EXTERNAL_STORAGE},...

android - Retrofit call void using Kotlin I'm with a problem with Retrofit 2. I want to use the Call to make a call without handle the response body, but it doesnt work with Kotlin. What I need to use instead of Void?

Kotlin Null safety warning Unexpected tokens (use ; to seperate expressions on the same line) I was trying Kotlin code in my application and received following warning: Unexpected tokens (use ; to seperate expressions on the same line) Code: var check: String var key: String = "KEY is" /*Warning coming on following statement*/ var str : String = check?key.replace("KEY", "ABDS-ASDSA-DSSS")?:check Any ideas how to resolve this?

Android Kotlin : TextView.text not working as expected I have an app that makes user sign in with Firebase if they are not already signed in. If user signs in their user profile info shows properly. Upon closing the app and reopening the user name and email does not set and goes to my defaulted text. But if I sign out and back in it will show. I feel like it has something to do with updating ui but stuck. I can post code after my lunch break is over if needed

Smart cast to kotlin.String I was trying Kotlin and got message from compiler: Smart cast to kotlin.String Code: /*"mTripStatus" is a nullable String*/ var html :String = HTML html = if (mTripStatus!=null) html.replace("TRIP_STATUS_VALUE", mTripStatus) else html What does this mean?