best kotlin tutorial

In Kotlin, we can compose an object into multiple variables: Data class Person (Val name:string= "Kotlin", Val sex:string= "man", Val age:int=1) Fun foo () { var (name, Sex,age) =person ()//Deconstruction Declaration print ("Name= $name sex= $sex age= $age") } This is the deconstruction declaration. A destructor declaration can declare multiple variables at once, and any expression can appear on t

Lambda with receiver* A method in the body of a lambda function that can invoke a different object without any additional qualifiers, which is not found in Java.* Such lambda is called "Lambda with receiver"Let's start with a normal function as a counter-example:Fun Alphabet (): String { val result = StringBuilder () for (letter in ' A ' ... ') Z ') { result.append (letter) } result.append ("\nnow, I know the alphabet") return result.tostring ()}In the above example, you ca

Kotlin Extension Kotlin can extend the properties and methods of a class and do not need to inherit.An extension is a static behavior that does not have any effect on the extended class code itself. Extension of the class, what a ghost. Anyway, I have never seen Java, the following look at the expansion of the Kotlin bar. I. Extension methods is to add a method.

Kotlin official website:https://kotlinlang.orgwe can get from GitHub Download . Currently The latest version is 1.1.2-5Https://github.com/JetBrains/kotlin/releases/tag/v1.1.2-5Pull down below and you can seeAfter downloading the extract, add the bin directory inside the path of the system environment variable, you can. Of course, the premise is that the system has built a Java environmentCMD input kotlinc-

Associated Objects analogy Java Do you still remember static statically members in Java? Attributes and methods declared as static idioms are initialized at class loading, parsing, and then their lifecycle is bound to the life cycle of the class. 1. This allows certain variables and methods in a class to be bound to the class, rather than bound to an object, to increase its life cycle. 2. This allows objects of this class to share this variable and method without allocating resources for eac

node of the layout file adds a custom namespace declaration, such as "xmlns:app=" Http://schemas.android.com/apk/res-auto "" and change the Android.support.v4.view.PagerTabStrip node name to the full path name of the custom view, such as "Com.example.custom.widget.PagerTab", At the same time, the new two attributes, App:textcolor and app:textsize, are specified under this node. The layout file code after the modification is as follows: The three steps of the custom attribute above, where the se

Forward pushDesign PatternsSimple Factory mode (Java and Kotlin Edition)Kotlin Basic KnowledgeKotlin first lesson: Starting with Java comparisonKotlin Introductory Lesson II: Collection OperationsKotlin Introductory Lesson Three: Data typesFirst attempt to implement Android projects with Kotlin1. DefinitionThe factory method pattern (Factory mode), also known as the factory pattern, is called the virtual Co

Using the Kotlin-kapt pluginRely on Java annotationprocessor instead of KAPTWhen using the control binding use, online search method, do not know by which guy with the pit.Error usage @BindView (r.id.tv_title) lateinit var tvtitle:textviewresult in the use of the control, there is no binding success, errorKotlin. Uninitializedpropertyaccessexception:lateinit property title had not been initializedCorrect useTv_title.settextcolor (color.red)Tv_title.s

Android-kotlin in fragment get ViewoverviewWhen using fragment, Butterknife was used to get the view but it went wrong, and then it was used to get the view directly using the Kotlin import layout, but it was wrong.ReasonThe reason is that the view is called in the Fragment Oncreateview method, which is obviously not possible because the view is not bound to the Fragment. So the initialization code can be p

1. ThreadJava notationNew Thread (New Runnable () {@Overridepublic void Run () {}}). Start (); Kotlin notationThread (Runnable { }). Start () 2, HandlerJavaPrivate Handler handler=new Handler (New Handler.callback () {@Overridepublic boolean handlemessage (Message msg) {Switch (msg.what) {Case 0:BreakDefaultBreak}return false;}}); KotlinPrivate Val Handler=handler (handler.callback{msg->When (Msg.what) {0->{}else->{}}False}) 3, SetonclicklistenerJavaB

Using Anko and Kotlin to develop databases on Android: SQLite is never an easy task (KAD25). ankokotlin By Antonio Leiva Time: Mar 30,201 7 Link: https://antonioleiva.com/databases-anko-kotlin/ The fact tells us that writing a database in Android is quite boring. When using SQLite, all the required templates are not the most pleasant thing in the world today. Fortunately, one of the items they announce

Getting Started Guide basic syntax definition packageThe declaration of the package must be at the top of the source file:Package My.demoImport java.util.*Java different packages do not have to match the directory structure: the source files can be placed anywhere on the file system.function definitionHere is an example of a parameter with two int types and an int return value:Fun sum (A:int, b:int): Int {Return a + b}Using an expression as a function body compiler can automatically infer the re

Examples of Spring Boot and Kotlin scheduled Tasks (Scheduling Tasks) and kotlinscheduling You may encounter such scenarios when writing Spring Boot applications. For example, you need to regularly send text messages, emails, and other operations, and you may also regularly check and monitor some labels and parameters. Create scheduled task Writing a scheduled task in Spring Boot is very simple. The following describes how to create a scheduled task i

function function Declaration Functions in Kotlin Use the FUN keyword declaration Fun double (x:int): Int { } function Usage Calling a function using the traditional method Val result = double (2) Call member functions using dot notation Sample (). Foo ()//Create class sample instance and call Foo infix notation Functions can also be called with infix notation when they are member functions or extension functions they have only one parameter

Before you read the following, you may need to understand some of the features of the Kotlin language: At the end of a statement, you can declare a method with the Fun keyword, and if the function is a method that overloads the parent class, you must also add the Override keyword. The parameter of the method is the first-write parameter name followed by the colon-and-write parameter type; The Kotlin source

A sealed class is used to represent a restricted class inheritance structure: When a value is a finite set ofType, and cannot have any other type. In a sense, they are extensions of the enumeration class: A collection of values for the enumeration typeis restricted, but there is only one instance of each enumerated constant, and the sealed classCan have multiple instances that can contain states. To declare a sealed class, you need to add the sealed modifier before the class name. Although seale

Defining local Variables Assign only one time (read-only) Local variables: Val a:int = 1 val b = 1//' Int ' type is inferred val c:int//type required when No. initializer is provided c = 1//definite assignment Variable variable var x = 5//' Int ' type is inferred x + = 1 Properties and Fields Defining propertiesYou can have properties in a class of Kotlin. These can be declared as mutable, using the Val keyword var keyword or read-only. p

Kotlin Object expressions and object declarations Kotlin uses object expressions and object declarations to implement an object that creates a class that makes minor changes to a class, and does not need to declare a new subclass. an object expression An object that implements an anonymous inner class through an object expression is used in the parameters of the method: Window.addmouselistener (Object:mous

Public Fun readbloghtml (blog:string): observable { return Observable.just (blog ), assembleurl (blog)} , readhtml (URL)}}I was a little confused ...And in fact Flatmap is not needed, because Kotlin read the source of the Web page is a word ... Public Fun readhtml (url:string): observable { return Observable.create { - subscriber.onnext (URL). ReadText ()); Subscriber.oncompleted () }}It's better

Antonio LeivaTime: Sep 12, 2016Original link: http://antonioleiva.com/recyclerview-diffutil-kotlin/As you know, the "Support Library 24" includes a new, applicable, and convenient class: Diffutil, which allows you to get rid of the boredom and error of cell changes and updates.If you don't know it yet, you can read Nicola Despotoski's good article about it. This article explains how easy it is to handle it.In fact, the Java language introduced many te