java - 无法从内部 Action 到达现场

Question

public class GameMenu extends JPanel{

    private final Core core;
    private final JButton loadGame;
    private final JButton saveGame;
    private final JButton exit;
    private final JButton newGame;

    public GameMenu(Core core){
        setPreferredSize(new Dimension(600, 600));
        setBackground(Color.BLACK);
        this.core = core;

        newGame = new JButton(newGameAction);
        loadGame = new JButton(loadGameAction);
        saveGame = new JButton(saveGameAction);
        exit = new JButton(exitGameAction);


        add(newGame);
        add(loadGame);
        add(saveGame);
        add(exit);
    }


  private Action newGameAction = new AbstractAction("New Game") {
        @Override
        public void actionPerformed(ActionEvent e) {          
            this.core.
        }
    };

嗨，我想调用一个核心方法而不是调用这个类的方法，这个方法会调用核心的正确方法 问题是我不知道如何到达核心领域，因为它找不到 谢谢

Answer 1

在这种情况下:

private Action newGameAction = new AbstractAction("New Game") {
    @Override
    public void actionPerformed(ActionEvent e) {          
        this.core. // compiling error here: 'core' is not a member of the anonymous inner class
    }
};

关键字this 指的是anonymous创建新的 Action 实例(当前对象)时生成的内部类。这个事实在这里解释:Using the this Keyword :

Within an instance method or a constructor, this is a reference to the current object — the object whose method or constructor is being called. You can refer to any member of the current object from within an instance method or a constructor by using this.

由于匿名内部类没有名为core 的成员，因此会出现编译错误。为了解决此问题，请查看此主题:Keyword for the outer class from an anonymous inner class? .

出于实际目的，您应该将上面的行替换为引用您的 GameMenu 类:

private Action newGameAction = new AbstractAction("New Game") {
    @Override
    public void actionPerformed(ActionEvent e) {          
        GameMenu.this.core. 
    }
};

或者您可以删除 this 关键字，编译器将为您解决同样的问题:

private Action newGameAction = new AbstractAction("New Game") {
    @Override
    public void actionPerformed(ActionEvent e) {          
        core. // should be recognised as outer class member
    }
};

鉴于匿名内部类没有核心成员，编译器将查找外部类(或最终层次结构树，具有适当的可见性)并检查是否有这样的成员，这确实如此。