Android Kotlin-1 基本語法2

下面內容有，最後更新於2020/12/06 16:19
1.class多建構式
2.內部class用法
3.enum class 用法
4.sealed class 用法
5.open 用法

1. class多建構式

    class InfoClass(private var name: String) {
        var number: Int = 1
        init {
            name = "Apple"
        }
        constructor(name: String, number: Int): this(name) {
            this.name = name
            this.number = number
        }
   
        fun getInfo() {
            println("name $name, number $number")
        }
    }
   
    val test = InfoClass("John")
    test.getInfo() //打印 name Apple, number 1
   
    val test2 = InfoClass("John",30)
    test2.getInfo() //打印 name John, number 30
   

2. 內部class用法

    class MainClass {
        var data = 10
        fun main() {
            val innerClass = InnerClass()
            data += innerClass.addFun()
            println("data = ${data}")
        }
        inner class InnerClass {
            var data = 1
            fun addFun(): Int {
                return data + 1
            }
        }
    }
   
    val mainClass = MainClass()
    mainClass.main() //打印 data = 12
   

3. enum class 用法

    enum class EnumClass(val index: Int) {
        Data1(0), Data2(1), Data3(2);
        fun getTag(): String {
            return "$index = $name"
        }
    }
   
    var tag = EnumClass.Data1.getTag()
    println(tag)//打印 0 = Data1
    tag = EnumClass.Data2.getTag()
    println(tag)//打印 1 = Data2
    tag = EnumClass.Data3.getTag()
    println(tag)//打印 2 = Data3
   

4. sealed class 用法

    sealed class SealedClass {
        data class onFinished(val data: Int): SealedClass()
        object onError: SealedClass()
    }
    fun createSealedClass(index: Int): SealedClass {
        when(index) {
            0 -> {
                return SealedClass.onFnished(30)
            }
            else -> {
                return SealedClass.onError
            }
        }
    }
   
    val sealedClass = createSealedClass(0)
    when(sealedClass) {
        SealedClass.onError -> {
   
        }
        //data class 這裡需要使用 is
        is SealedClass.onFnished -> {
            //打印 30
            println("data = ${sealedClass.data}")
        }
    }
   

5. open 用法

    //open class 才可以給class繼承
    //open fun 才可以繼承方法改寫
    open class BaseClass {
        open fun test1(value: Int) {
            //打印 BaseClass test1 20
            println("BaseClass test1 $value")
        }
   
        fun test2(value: Int) {
            //打印 BaseClass test2 25
            println("BaseClass test2 $value")
        }
    }
    //使用override繼承
    class TextClass: BaseClass() {
        override fun test1(value: Int) {
            super.test1(value)
            //打印 BaseClass test1AA 30
            println("BaseClass test1AA ${value+10}")
        }
    }
   
    val testClass = TextClass()
    testClass.test1(20)
    testClass.test2(25)
    //最後打印
    /*
    BaseClass test1 20
    BaseClass test1AA 30
    BaseClass test2 25
    */