LIPNUS

1. lateinitprivate lateinit var toolbar: Toolbar fun someMethod() { toolbar = findViewById(R.id.home_toolbar) as Toolbar } 2. by lazyprivate val toolbar by lazy { findViewById(R.id.home_toolbar) as Toolbar }변수가 사용되는 시점에 연산이 일어남.위에꺼보다 제약조건이 더 적음. 동기화도 해준다.

1. let val num: Int = (a*b - 2*a) testFunction(num) (a*b - 2*a).let{ testFunction(it) val padding = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 16f, resources.displayMetrics).toInt() // 왼쪽, 오른쪽 padding 설정 setPadding(padding, 0, padding, 0) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 16f, resources.displayMetrics).toInt().let { padding -> // 계산된 값을 padding 이라는 이름의 인자로 받음 set..

fun AAA(num: Int): ()-> Unit = { println(num) } fun main(args: Array){ val f: () -> Unit = AAA(30) f() }

fun decorate(task:() -> Unit){ println("=== 작업시작 ===") task() println("=== 작업 끝 ===") } fun main(args: Array){ decorate({ val a = 10 val b=5 println("a+b는 $a + $b") }) decorate({ println("some") println("task") }) }

1. 람다식 & 익명함수 fun main(args: Array){ val instantFunc: (Int) -> Unit = { number:Int -> println("값: $number") } instantFunc(1) instantFunc.invoke(1) val instantFunc2: (Int) -> Unit = fun(number:Int): Unit{ println("값: $number") } instantFunc2(2) instantFunc2.invoke(2) } 2. it식별자fun main(args: Array){ val instantFunc: (Int)-> Unit = { println("값: $it") } instantFunc }람다식의 매개변수가 하나뿐일 때 3. 안드로이드에서의 예시

class Person private constructor(){ companion object { fun create(): Person{ countCreated++ return Person() } var countCreated = 0 private set } } fun main(args: Array){ val a = Person.create() val b = Person.create() println(Person.countCreated) }

1.업캐스팅(Upcasting)open class Person(val name: String, val age: Int) class Student(name: String, age: Int, val id: Int): Person(name, age) fun main(args: Array){ val p1: Person = Student("선필", 30, 2013210059) } 출처: 초보자를 위한 Kotlin 200제, 정보문화사. p177 슈퍼클래스타입은 항상 슈퍼클래스 자체나 서브클래스의 인스턴스만 가질 수 있다. 2.as 연산자와 다운캐스팅open class Person(val name: String, val age: Int) class Student(name: String, age: Int, val i..

인도형님 유튜브: https://www.youtube.com/watch?v=HZuWeJ_Sa5A공식사이트: https://google.github.io/ExoPlayer/ 1.Gradleimplementation 'com.google.android.exoplayer:exoplayer:2.9.1'이걸 하니까 implementation 'com.android.support:appcompat-v7:27.1.1'이 부분에서 에러가 났는데 버전을 똑같이 27.1.1로 바꿔주니까 된다. compileOptions { sourceCompatibility JavaVersion.VERSION_1_8 targetCompatibility JavaVersion.VERSION_1_8 }이 부분을 꼭 넣어줘야 한다. androi..

JAVAIntent iT = new Intent(this, OtherActivity.class); startActivity(iT); Kotlinval iT = Intent(this, NextActivity::class.java) intent.putExtra("Key", value) startActivity(iT) var a: String = intent.getStringExtra("Key")

요 플러그인을 사용하면 된다.

1. Gradleimplementation 'com.squareup.retrofit2:retrofit:2.5.0' implementation 'com.squareup.retrofit2:converter-gson:2.5.0' 2. Permission 3. Interface(Retrofit)interface RetrofitImageAPI { @GET("api/RetrofitAndroidImageResponse") fun getImageDetails(): Call } 4. MainActivity.ktclass MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedIns..

1.Permission 2.WebViewclass MainActivity : AppCompatActivity() { @RequiresApi(Build.VERSION_CODES.KITKAT) override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) setButtons() setWebView() } fun setWebView(){ var url: String? = "https://naver.com" // 웹뷰의 인스턴스를 가져온다 val settings = webView.settings // 자바스크립트 사용가능 유무 settings.jav..

1. Gardle implementation 'org.jsoup:jsoup:1.11.3'공식사이트: https://jsoup.org/ 2. Manifest 3. Activityclass MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) // testJsoup() selectTest() } fun selectTest(){ object : Thread() { override fun run() { val response = Jsoup.connect("http://www...

while ((c = inputStream!!.read()) != -1) { outputStream.write(c) }이거 안되서 한참 고민. Kotlin은 while안에서 assign이 안된다. do{ c = inputStream.read() outputStream.write(c) } while(c != -1)이렇게 고치면 가능. 사람들은 이런 의견을 내고 있다. Wasabi375May 11The Kotlin team decided against it for a few reasons I think. In most cases it is just considered bad style and it also makes code harder to read. Yes your example is the one va..

https://thdev.tech/kotlin/2016/08/02/Basic-Kotlin-01/

val hashMap:HashMap = HashMap() //define empty hashmap hashMap.put(1,"Ajay") hashMap.put(3,"Vijay") hashMap.put(4,"Praveen") hashMap.put(2,"Ajay") println(".....traversing hashmap.......") for(key in hashMap.keys){ println("Element at key $key = $") ​ https://www.javatpoint.com/kotlin-hashmap

코틀린으로 구현한 Retrofit.공식사이트: https://square.github.io/retrofit/ 1.Gradleimplementation 'com.squareup.retrofit2:retrofit:2.5.0' implementation 'com.squareup.retrofit2:converter-gson:2.5.0'두개의 버전은 일치시켜 준다. 2.Manifests 3.XML버튼 두개 만들어준다. 3.RetrofitService.ktdata class ResponseDTO(var result:String? = null) interface RetrofitService{ //post @FormUrlEncoded @POST("/test") fun postRequest(@Field("id") id:..

*Glide Document: https://bumptech.github.io/glide/ 버전이 올라가면서 예전에 쓰던거에서 사용법이 약간 바뀌었다.implementation 'com.github.bumptech.glide:glide:4.8.0' annotationProcessor 'com.github.bumptech.glide:compiler:4.8.0' implementation 'jp.wasabeef:glide-transformations:4.0.1'(세번째꺼는 Glide확장판? 같은 거) 1.PlaceholderGlide.with(this) .load("경로") .apply(RequestOptions().placeholder(R.drawable.s1)) .into(main_iv) 2.Center..

package com.example.lipnus.button import android.support.v7.app.AppCompatActivity import android.os.Bundle import android.widget.Toast import kotlinx.android.synthetic.main.activity_main.* class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) lipnus_button.setOnClickListener(){ Toa..

일반 클래스class Student { var name: String? = null var subject: Subject? = null class Subject { var math : Int? = null var english : Int? = null } } fun main(args: Array){ var s = Student() s.name = "선필" var sub = Student.Subject() sub.math = 90 sub.english = 96 s.subject = sub println("${s.name}의 점수: ${s.subject?.math}, ${s.subject?.english} ") }선필의 점수: 90, 96 // s.subject = sub이 부분을 주석처리하면 null Sa..