如何在Kotlin中创建一个抽象类的匿名类实例？ [英] How to create an instance of anonymous class of abstract class in Kotlin?

问题描述

假设 KeyAdapter 是一个抽象类，有几个方法可以被覆盖。

Assume that KeyAdapter is an abstract class with several methods that can be overridden.

在java中我可以执行：

In java I can do:

KeyListener keyListener = new KeyAdapter() {
    @Override public void keyPressed(KeyEvent keyEvent) {
        // ...
    }
};

如何在Kotlin中做同样的事情？

How to do the same in Kotlin?

推荐答案

来自官方Kotlin语言文档和Google上的首批点击之一：

From the official Kotlin language documentation and one of the first hits on Google:

window.addMouseListener(object : MouseAdapter() { 
    override fun mouseClicked(e : MouseEvent) { 
    // ... 
}

适用于您手头的问题：

val keyListener = object : KeyAdapter() { 
    override fun keyPressed(keyEvent : KeyEvent) { 
    // ... 
} 

正如Peter Lamberg指出的那样 - 如果匿名类实际上是功能接口的实现（即不是抽象类）， SAM转换可用于进一步简化此声明：

As Peter Lamberg has pointed out - if the anonymous class is actually an implementation of a functional interface (i.e. not of an abstract class), SAM Conversions can be used to simplify this statement even further:

val keyListener = KeyAdapter { keyEvent ->
    // ...
}

请注意此讨论关于Java中定义的接口的不同用法和Kotlin。

Please also note this discussion about the different usage of interfaces defined in Java and Kotlin.

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