如何在 Kotlin 中创建抽象类匿名类的实例? [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，有几个可以覆盖的方法.

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

在java中我可以做到:

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:

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

应用于您手头的问题:

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

正如 Peter Lamberg 所指出的 - 如果匿名类实际上是函数接口的实现(即不是抽象类)，SAM Conversions 可用于进一步简化此语句:

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 ->
    // ...
}

另请注意此讨论 关于 Java 和 Kotlin 中定义的接口的不同用法.

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

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