Since mMeshes is a var property, it can change between the assignment of mutableListOf(AiMesh()) and the usage in pScene.mMeshes[0], meaning that it is not guaranteed to be not-null at the use site. The compiler enforces null-safety, treating pScene.mMeshes as nullable MutableList<AiMesh>? and not allowing you to use it as MutableList<AiMesh> (i.e. it cannot safely perform … Read more
TL;DR: The field: part is known as a “use-site target”, and makes it clear that the annotation is applied to the backing field of the Kotlin property. It is not strictly necessary in this case, though it can make the code more readable. Explanation To simplify, let’s say you have: data class Repo( @field:SerializedName(“name”) var … Read more
In Java, you can only capture (effectively) final variables in anonymous classes and lambdas. In Kotlin, you can capture any variable, even if they are mutable. This is done by wrapping any captured variables in instances of simple wrapper classes. These wrappers just have a single field that contains the captured variables. Since the instances … Read more
You can use a raw string which is more readable anyway: @Dao interface ItemDao { @Query(“”” SELECT * FROM Item WHERE Item.id = :id “””) fun loadItemById(id: Long): LiveData<Item> }
Use Long.toInt(): process((System.currentTimeMillis() / 1000 / 60).toInt())
Using java.security.MessageDigest is the simplest way import java.math.BigInteger import java.security.MessageDigest fun md5(input:String): String { val md = MessageDigest.getInstance(“MD5”) return BigInteger(1, md.digest(input.toByteArray())).toString(16).padStart(32, ‘0’) }
You can use the .sum() function to sum all the elements in an array or collection of Byte, Short, Int, Long, Float or Double. (docs) For example: val myIntList = listOf(3, 4, 2) myIntList.sum() // = 9 val myDoubleList = listOf(3.2, 4.1, 2.0) myDoubleList.sum() // = 9.3 If the number you want to sum is … Read more
The extension withLock works on Lock instances like ReentrantLock, whereas synchronized may be used with any object. val lock = ReentrantLock() fun syncWithLockTest(): Int = lock.withLock { 123 } val anyLock = Any() fun syncWithArbitraryObjTest(): Int = synchronized(anyLock) { 123 } Note that synchronized is a function in Kotlin which returns a value. This makes … Read more
Closing a channel conceptually works by sending a special “close token” over this channel. You close a channel when you have a finite sequence of elements to be processed by consumers and you must signal to the consumers that this sequence is over. You don’t have to close a channel otherwise. Channels are not tied … Read more
const vals cannot be in a class. For you, this means you need to declare it top-level, in an object, or in a companion object (which also is exactly what the error message says). Since your value is private, a companion object is one of the two options you can use: class TradersActivityTest { … … Read more