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Kotlin 注解 第三篇 @JvmField 与 @JvmStatic - 技术小黑屋

 4 years ago
source link: https://droidyue.com/blog/2019/12/22/kotlin-annotation-jvmfiled-and-jvmstatic-and-object/?
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本文是既 JvmName 注解在 Kotlin 中的应用和JvmMultifile 注解在 Kotlin 中的应用的第三篇关于 Kotlin的注解文章。

介绍的内容比较简单，主要是包含了JvmField和JvmStatic两个。

@JvmField

示例代码声明

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package com.example.jvmannotationsample

class Developer (@JvmField val name: String, val ide: String)

使用@JvmField，我们在Java中调用的时候，可以直接使用属性名，而不是对应的getter方法。

调用代码对比

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//test jvmField
Developer developer = new Developer("Andy", "Android Studio");
System.out.println(developer.getIde());// not using JvmField
System.out.println(developer.name);// using JvmField

@JvmStatic

除此之外，对于静态属性和静态方法的实现，我们也可以使用@JvmStatic实现，

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package com.example.jvmannotationsample

class Sample {
    companion object {
        @JvmStatic
        val TAG_NAME = "Sample"

        val NON_STATIC_VALUE = "non_static_value"

        @JvmStatic fun callStatic() {

        }

        fun callNonStatic() {

        }
    }
}

调用代码如下

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//JVM static method
Sample.callStatic();
Sample.Companion.callNonStatic();

Sample.getTAG_NAME();
Sample.Companion.getNON_STATIC_VALUE();

Companion

Kotlin中我们可以借助object实现静态的形式，比如下面的代码

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package com.example.jvmannotationsample

class SomeClass {
    companion object {
        fun getCommonProperties(): List<String> {
            return emptyList()
        }
    }
}

其实除此之外，我们还能命名companion的名称,如下代码

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package com.example.jvmannotationsample

class AnotherClass {
    companion object Assistant {
        fun scheduleSomething() {

        }
    }
}

调用代码示例

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//test companion
SomeClass.Companion.getCommonProperties();
AnotherClass.Assistant.scheduleSomething();

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