'this'关键字的范围问题

Question

我正在尝试创建自己的窗口类,扩展JFrame.但是,我遇到了动作监听器的问题fullScreenBtn.在编写ActionListener.actionPerformed函数时,我无法使用this它所引用的关键字new ActionListener.我如何参考实例MyWindow？

public class MyWindow extends JFrame {
    private static GraphicsEnvironment gEnv = GraphicsEnvironment.getLocalGraphicsEnvironment();
    private static GraphicsDevice gDev = gEnv.getDefaultScreenDevice();
    private static JPanel toolbar = new JPanel();
    private static JButton fullScreenBtn = new JButton("Show Full Screen");
    private static boolean isFullScreen = false;

    public MyWindow() {
        toolbar.setLayout(new FlowLayout());
        this.getContentPane().add(toolbar, BorderLayout.PAGE_START);

        fullScreenBtn.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                // Toggle full screen window
                this.setUndecorated(!isFullScreen);
                this.setResizable(isFullScreen);
                gDev.setFullScreenWindow(this);

                isFullScreen = !isFullScreen;

                if (isFullScreen) {
                    fullScreenBtn.setText("Show Windowed");
                } else {
                    fullScreenBtn.setText("Show Full Screen");
                }
            }
        });

        this.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent windowEvent) {
                this.dispose();
                System.exit(0);
            }
        });
    }
}

Answer 1

在内部类中this,如果需要获取对外部类的引用,则需要在外部类的类名前面使用它:例如,使用

MyWindow.this.setUndecorated(...)` 
//  etc...

顺便说一句,你真的不想在这里扩展JFrame,在大多数情况下.

此外,保存JButton的祖先窗口可以通过其他方式获得,例如via SwingUtilities.getWindowAncestor(theButton).即

        public void actionPerformed(ActionEvent e) {
            Object source = e.getSource();
            if (source instanceof JButton) {
              JButton button = (button) source;
              Window ancestorWin = SwingUtilities.getAncestorWindow(button);
              ancestorWin.setUndecorated(!isFullScreen);
              ancestorWin.setResizable(isFullScreen);
              // etc...

或者,如果您最清楚地知道祖先窗口是JFrame:

        public void actionPerformed(ActionEvent e) {
            Object source = e.getSource();
            if (source instanceof JButton) {
              JButton button = (button) source;

              JFrame ancestorWin = (JFrame) SwingUtilities.getAncestorWindow(button);
              ancestorWin.setUndecorated(!isFullScreen);
              ancestorWin.setResizable(isFullScreen);
              // etc...