如何在Kotlin中创建匿名接口的实例？ [英] How to create an instance of anonymous interface in Kotlin?

问题描述

我有第三方Java库，其对象具有如下界面：

I have a third party Java library which an object with interface like this:

public interface Handler<C> {
  void call(C context) throws Exception;
}

如何在Kotlin中简洁地实现它，类似于Java匿名类，如下所示：

How can I concisely implement it in Kotlin similar to Java anonymous class like this:

Handler<MyContext> handler = new Handler<MyContext> {
   @Override
   public void call(MyContext context) throws Exception {
      System.out.println("Hello world");
   }
}

handler.call(myContext) // Prints "Hello world"

推荐答案

假设界面只有一种方法，你可以使用 SAM

Assuming the interface has only a single method you can make use of SAM

val handler = Handler<String> { println("Hello: $it")}

如果你有一个接受处理程序的方法那么你甚至可以省略类型参数：

If you have a method that accepts a handler then you can even omit type arguments:

fun acceptHandler(handler:Handler<String>){}

acceptHandler(Handler { println("Hello: $it")})

acceptHandler({ println("Hello: $it")})

acceptHandler { println("Hello: $it")}

如果接口有多个方法，语法有点更详细：

If the interface has more than one method the syntax is a bit more verbose:

val handler = object: Handler2<String> {
    override fun call(context: String?) { println("Call: $context") }
    override fun run(context: String?) { println("Run: $context")  }
}

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