java - Java 中使用 JFrame 的监听器

Question

我现在正在学习 ActionListeners 的基础知识，并且一直在这里寻求帮助，但无法完全找到/弄清楚我做错了什么。

我有一个实现主调用的类(客户端):

...
public static void main(String[] args) {

    Myframe test = new Myframe();

    N = test.setVisible(); // N is an integer

...
}

然后是我框架中的代码:

public class test extends JFrame {

    private JPanel contentPane;
    private int N;

    public int setVisible(){

        this.setVisible(true);
        return N;

    }

    /**
     * Create the frame.
     */
    public test() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 450, 300);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        contentPane.setLayout(new BorderLayout(0, 0));
        setContentPane(contentPane);

        JButton btnOk = new JButton("OK");
        btnOk.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {

                N=5;
                dispose();

            }
        });
        contentPane.add(btnOk, BorderLayout.SOUTH);
    }

}

问题是:程序在继续运行之前不会等待按下按钮，并且 N 会产生一些垃圾值，从而产生错误。我应该怎么做才能让它正确处理它而不 hibernate 线程？

Answer 1

解决这个问题的一些方法。使用 JDialog - 默认提供模式阻塞，监听器机制 - 稍后回调值，或者使你的代码阻塞

JDialog

public class test extends JDialog {
    ...    
    private int N;

    public int setVisible() {
        this.setVisible(true);
        return N;
    }

    public test() {
        super(null, ModalityType.APPLICATION_MODAL); 
        // <== pass parent window here if you have one, you don't seem to.. 
        ...
    }

阻止示例

• 使用java.util.concurrent.CountDownLatch

代码

public class test extends JFrame {
    ....    
    private CountDownLatch latch;
    private int N;

    public int setVisible() throws InterruptedException{

        latch = new CountDownLatch(1);
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                setVisible(true);
            }
        });

        latch.await();   // <== block until countDown called
        return N;
    }

    public test() {           
        ...
        btnOk.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {

                N=5;
                latch.countDown();   <== will unblock await() call
                dispose();

            }
        });
        ...
    }

}

监听器

public class test extends JFrame {
    ... 
    private Listener listener;

    public static interface Listener {
        void setN(int n);
    }

    public void setVisible(Listener listener) throws InterruptedException {
        this.listener = listener;   // <== save reference to listener
        setVisible(true);
    }

    public test() {
        ...
        btnOk.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {

                listener.setN(5);  // <== call listener
                dispose();

            }
        });
    }