Kotlin:接口......没有构造函数 [英] Kotlin: Interface ... does not have constructors

问题描述

我正在将一些 Java 代码转换为 Kotlin，但我不太明白如何实例化在 Kotlin 代码中定义的接口.例如，我有一个接口(在 Java 代码中定义):

I am converting some of my Java code to Kotlin and I do not quite understand how to instantiate interfaces that are defined in Kotlin code. As an example, I have an interface (defined in Java code):

public interface MyInterface {
    void onLocationMeasured(Location location);
}

然后在我的 Kotlin 代码中进一步实例化这个接口:

And then further in my Kotlin code I instantiate this interface:

val myObj = new MyInterface { Log.d("...", "...") }

而且它工作正常.但是，当我将 MyInterface 转换为 Kotlin 时:

and it works fine. However, when I convert MyInterface to Kotlin:

interface MyInterface {
    fun onLocationMeasured(location: Location)
}

我收到一条错误消息:当我尝试实例化它时，Interface MyListener 没有构造函数 - 尽管在我看来，除了语法之外没有任何变化.我是否误解了接口在 Kotlin 中的工作原理?

I get an error message: Interface MyListener does not have constructors when I try to instantiate it - though it seems to me that nothing has changed except syntax. Do I misunderstand how interfaces work in Kotlin?

推荐答案

您的 Java 代码依赖于 SAM 转换 - 将 lambda 自动转换为具有单个抽象方法的接口.Kotlin 中定义的接口目前不支持 SAM 转换.相反，您需要定义一个实现该接口的匿名对象:

Your Java code relies on SAM conversion - an automatic conversion of a lambda into an interface with a single abstract method. SAM conversion is currently not supported for interfaces defined in Kotlin. Instead, you need to define an anonymous object implementing the interface:

val obj = object : MyInterface {
    override fun onLocationMeasured(location: Location) { ... }
}

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