如何在 kotlin 中使用 Android Support typedef 注释? [英] How to use Android Support typedef annotations in kotlin?

问题描述

我开发Android应用程序，经常使用注解作为编译时参数检查，主要是android的支持注解.

java 代码示例:

公共类测试{@IntDef({Speed.SLOW,Speed.NORMAL,Speed.FAST})公共@interface 速度{public static final int SLOW = 0;public static final int NORMAL = 1;public static final int FAST = 2;}@速度私有int速度；public void setSpeed(@Speed int speed){this.speed = 速度；}}

我不想使用枚举，因为它们在 Android 中存在性能问题.kotlin 的自动转换器只会生成无效代码.如何在 kotlin 中使用 @IntDef 注释?

解决方案

如果您错过了对问题或此答案的评论，请注意以下技术编译，但不会创建您将获得的编译时验证Java(部分违背了这样做的目的).考虑使用 enum班级相反.

<小时>

实际上可以通过将注释类的外部值定义为 const vals 来使用 @IntDef 支持注释.

使用您的示例:

import android.support.annotation.IntDef公共类测试{伴生对象{@IntDef(慢，正常，快)@Retention(AnnotationRetention.SOURCE)注释类 Speed常量值慢 = 0Lconst val 正常 = 1L常量值快速 = 2L}@速度私有 lateinit var 速度:长公共乐趣 setSpeed(@Speed speed: Long) {this.speed = 速度}}

请注意，此时编译器似乎需要 @IntDef 注释的 Long 类型，而不是实际的 Int .>

I develop Android applications and often use annotations as compile time parameter checks, mostly android's support annotations.

Example in java code:

public class Test
{
    @IntDef({Speed.SLOW,Speed.NORMAL,Speed.FAST})
    public @interface Speed
    {
         public static final int SLOW = 0;
         public static final int NORMAL = 1;
         public static final int FAST = 2;
    }

    @Speed
    private int speed;

    public void setSpeed(@Speed int speed)
    {
        this.speed = speed;
    }
}

I don't want to use enums because of their performance issues in Android. The automatic converter to kotlin just generates invalid code. How do I use the @IntDef annotation in kotlin?

解决方案

Edit: In case you miss the comments on the question or this answer, it's worth noting that the following technique compiles, but does not create the compile-time validation you would get in Java (which partially defeats the purpose of doing this). Consider using an enum class instead.

---

It is actually possible to use the @IntDef support annotation by defining your values outside of the annotation class as const vals.

Using your example:

import android.support.annotation.IntDef

public class Test {

    companion object {

         @IntDef(SLOW, NORMAL, FAST)
         @Retention(AnnotationRetention.SOURCE)
         annotation class Speed

         const val SLOW = 0L
         const val NORMAL = 1L
         const val FAST = 2L
    }

    @Speed
    private lateinit var speed: Long

    public fun setSpeed(@Speed speed: Long) {
        this.speed = speed
    }
}

Note that at this point the compiler seems to require the Long type for the @IntDef annotation instead of actual Ints.

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