kotlin

问题 I have a MutableMap<CryptoTypes, CurrentTradingInfo> that I'm wanting to save in onSaveInstanceState and was going to use Moshi to convert back and forth. CryptoTypes is an ENUM private var tickerData: MutableMap<CryptoTypes, CurrentTradingInfo> = mutableMapOf() fun convertTickerDataJson(): String { val moshi = Moshi.Builder().build() val jsonAdapter = moshi.adapter<MutableMap<CryptoTypes, CurrentTradingInfo>>(MutableMap::class.java) return jsonAdapter.toJson(tickerData) } fun

问题 Let's assume I'm writing a library that returns a string which is a complex and long running task. I can chose between offering this interface StringGenerator { suspend fun generateString(): String } or interface StringGenerator { fun generateString(): Deferred<String> } Are there any (dis-)advantages of either of the options and which are they? Which should I choose? 回答1: Kotlin coroutines are designed along the "sequential by default" guideline. That means that your API should always expose

问题 I want to have a base activity class that takes care of some initialization I started defining it like this. abstract class BaseActivity<VIEW_MODEL : ViewModel, BINDING : ViewDataBinding> : AppCompatActivity() { lateinit var viewmodel: VIEW_MODEL lateinit var binding: BINDING lateinit var glide: RequestManager @get:LayoutRes abstract val layoutResource: Int override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) binding = DataBindingUtil.setContentView(this,

问题 I want to have a base activity class that takes care of some initialization I started defining it like this. abstract class BaseActivity<VIEW_MODEL : ViewModel, BINDING : ViewDataBinding> : AppCompatActivity() { lateinit var viewmodel: VIEW_MODEL lateinit var binding: BINDING lateinit var glide: RequestManager @get:LayoutRes abstract val layoutResource: Int override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) binding = DataBindingUtil.setContentView(this,

问题 I have the following code, that I do not understand, why it is not a tail recursion: override fun drop(n: Int): List<A> = if (n == 0) this else tail.drop(n - 1) whereas this is a tail recursion: fun drop(n: Int): List<A> { tailrec fun drop(n: Int, list: List<A>): List<A> = if (n <= 0) list else when (list) { is Cons -> drop(n - 1, list.tail) is Nil -> list } return drop(n, this) } Why is the first example not a tail recursion? 回答1: It isn't tail recursion because Kotlin checks the recursive

问题 I need to implement a button in my app like this I used a SwitchCompat button but the closest I arrived was to this point, having two main problems: 1 - The width of the button does not adjust correctly when screen sizes change (drawable gets cut off, become too small etc), it is important that the width occupies the parent view correctly ( a small linear layout enclosing it) 2 - I was not able to understand how I could get the letters in the Switch Track Is it possible to achieve this result

问题 I have a RecyclerView that I want to start showing the bottom items, so I'm using: myLayoutManager.setStackFromEnd(true) . It works just as I want when there are enough items to fill the screen, but if there are only a few items in the RecyclerView, it pushes them down and leaves empty space at the top of the screen Is there any way prevent this, or to only setStackFromEnd if the RecyclerView is larger than the screen height? Here's an example of what I get and what I'm trying to get: 回答1:

问题 I have a RecyclerView that I want to start showing the bottom items, so I'm using: myLayoutManager.setStackFromEnd(true) . It works just as I want when there are enough items to fill the screen, but if there are only a few items in the RecyclerView, it pushes them down and leaves empty space at the top of the screen Is there any way prevent this, or to only setStackFromEnd if the RecyclerView is larger than the screen height? Here's an example of what I get and what I'm trying to get: 回答1:

问题 I am having a simple controller class @RestController open class MyController() { @Autowired lateinit var myInterface: MyInterface @GetMapping(value = ["/v1/call-Api"], produces = ["application/json"]) fun getData():Response{ callFx() /// Here I have logic } fun callFx():String{ return myInterface.getmyStringData() } } Now Come to implementation part of MyInterface @Service class MyImpl: MyInterface { override fun getmyStringData(){ return "Some string" } } Please note that for MyInterface ,

问题 We have a package that we are looking to convert to kotlin from python in order to then be able to migrate systems using that package. Within the package there are a set of classes that are all variants, or 'flavours' of a common base class. Most of the code is in the base class which has a significant number of optional parameters. So consider: open class BaseTree(val height:Int=10,val roots:Boolean=true, //...... lots more!! class FruitTree(val fruitSize, height:Int=10, roots:Boolean=true,