Kotlin使用总结

  • Any所有类的基类
  • object - 单例
  • Kotlin的类默认不能继承，只有被open修饰的类能继承。继承类时，类后面要跟()

  • var & val & const

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    var //读写
    val //只读
    const val //static final

  • companion object - static

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    companion object {
        private val TAG = "xxx"
    }

  • constructor & init

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    class Xxx constructor(id:Int,name:String) {}
    class Xxx(id:Int,name:String) {}
    init {}

  • 字符串拼接

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    "${str1}连接符${it.value}"

  • with

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    with (container.titles_panel) {
        visibility = View.VISIBLE
        title.text = data.title
    }

  • run, with, let, also, apply

    image

    图片来源

  • if expression

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    val max = if (num1 > num2) num1 else num2

  • when取代java中的switch

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    when(case) {
        case1 -> xxx
        case2,case3 -> xxx
        else -> xxx
    }

  • elvis operator

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    return response.body()?.string() ?: "fail"

  • getOrPut - return value

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    xxxMap.getOrPut(key) { mutableSetOf() }

  • takeIf - T.takeIf return T

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    stripViewCache.takeIf { stripViewCache.size <= index }.add(xxxView())

  • mapOf

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    mapOf("key" to "value", "key" to "value")

  • Kotlin关键字

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    import org.mockito.Mockito.`when` as whenever

  • lazy

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    private val presenter by lazy { XxxPresenter(this) }