kotlin | 易学教程

Gson deserialize Array of Integers in kotlin

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问题 Normally, when I deserialize a json-String I use something like this: val result = gson.fromJson<myObject>(json, object : TypeToken<myObject>() {}.type) But now I want to deserialize a simple List of Int and I cannot build an object for that. The json-String is extremely simple and looks like this: [1,35,37,255] and I would like to save it into a List but val result = gson.fromJson<List<Int>>(json, object : TypeToken<List<Int>>() {}.type) does not work because there is no object. How should I

How to find a child Fragment with Navigation Architecture components

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问题 After learning basics about new architecture components, I decided to apply this knowledge and work a demo project. In this project I have been working with google map. In my navHost fragment, one of the fragment shows google map this way <fragment android:layout_width="match_parent" android:layout_height="match_parent" android:id="@+id/map" android:name="com.google.android.gms.maps.SupportMapFragment"></fragment> from the code I have been trying to get this fragment class, the related code

How to find a child Fragment with Navigation Architecture components

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Spring not null validation throwing HttpMessageNotReadableException instead of MethodArgumentNotValidException in kotlin

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问题 I'm making and simple application in Kotlin using Spring but I'm having a problem with the validation. I have this entity class: @Entity @Table(name = "category") data class Category( @Id @GeneratedValue(strategy = GenerationType.IDENTITY) val id: Long?, @field:NotNull @field:NotEmpty val name: String) And my controller function like this: @PostMapping @ResponseStatus(HttpStatus.CREATED) fun create(@Valid @RequestBody category: Category): ResponseEntity<Category> create have some code, but it

Changing MainActivity entry while integrating React native and android application

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问题 I am are working on POC to integrate native android app with React Native. After following all steps in react native official docs for integration, I had an error MainActivity.java does not exist. Not sure but I guess its cosreact-native run-android works through MainActivity.java. But in native android app we dun have any such activity file. From AndroidManifest.xml it looks this is the first activity: <application android:name=".core.exampleApplication" so to customize to this activity file

Unable to refresh recyclerView with pagination

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问题 I have a RecyclerView that gets filled with paginated data. I need to be able to refresh it via SwipeRefreshLayout , but so far, I am unable to do so. I have tried plenty references that does similar to this, but without any success. Also, for letting you guys know, When I do refresh, the data gets retrieved correctly, but it is not being displayed on the recyclerView... Also, when I move from that destination to another via Navigation and then, I hit back, it gets updated. I am not sure what

Unable to refresh recyclerView with pagination

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Kotlin与java8的SAM转换对比

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什么是sam 转换 Single Abstract Method 实际上这是java8中提出的概念，你就把他理解为是一个方法的接口的就可以了看一下我们每天都在使用的线程池 ExecutorService executorService= Executors.newScheduledThreadPool(3 ); executorService.execute( new Runnable() { @Override public void run() { System.out.println( "hello world" ); } }); 用下面的java8中的lambda 来写也是可以的。 executorService.execute(()->System.out.println("hello world")); 所以说这两种写法是等价的。但是这里要强调的是 java中的lambda是没有类型的，所以他必须需要一个接口来接受他。 kotlin中的sam val executorService: ExecutorService = Executors.newScheduledThreadPool(3 ) // kotlin中的匿名内部类的标准写法 executorService.submit(object :Runnable{ override fun run()

Kotlin make constructor of data class accept both List and MutableList but store a mutable instance of them

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问题 I want to make a data class which can accept both list and mutable-list and if the list is instance of MutableList then directly make it a property else if it is a List then convert it into a MutableList and then store it. data class SidebarCategory(val title: String, val groups: MutableList<SidebarGroup>) { constructor(title: String, groups: List<SidebarGroup>) : this(title, if (groups is MutableList<SidebarGroup>) groups else groups.toMutableList()) } In the above code Platform declaration

Kotlin make constructor of data class accept both List and MutableList but store a mutable instance of them

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