java - 程序在调用 wait() 时停止；在java中

Question

我已同步此代码以使用等待和通知，但现在当我通过单击等待按钮调用 wait() 时，程序停止执行(程序挂起)。请帮忙，不要建议我使用不同的链接，请修复此代码并回答。

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;


public class Main extends JFrame implements ActionListener, Runnable {


    JLabel time = new JLabel();
    JButton wait = new JButton("wait");
    JButton notify = new JButton("notify");
    Thread count = new Thread(this);
    int sec=0;


    public static void main(String arg[]) {
        new Main();
    }


    public Main() {
        super("Counter");
        setSize(250,100);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setLayout(new FlowLayout());
        setVisible(true);
        add(time);
        add(wait);
        add(notify);
        notify.setEnabled(false);
        wait.addActionListener(this);
        notify.addActionListener(this);
        count.start();
    }


    public void actionPerformed(ActionEvent e) {

        synchronized(count) {
            if(e.getSource()==wait) {
                try
                {
                    count.wait();
                    wait.setEnabled(false);
                    notify.setEnabled(true);
                }
                catch (Exception e1) {
                    e1.printStackTrace();
                }
            }

            else if(e.getSource()==notify) {
                count.notify();
                wait.setEnabled(true);
                notify.setEnabled(false);
            }

        }
    }



    public void run() {

        synchronized (this) {           
            while(true) {
                time.setText(String.format("seconds=%d",sec));
                try
                {
                    Thread.sleep(1000);
                }
                catch (InterruptedException e) {
                    e.printStackTrace();
                }
                sec++;
            }
        }   
    }
}

Answer 1

当您调用 wait() 时，您将阻塞 EDT。当您尝试 notify() 时，它将不起作用，因为负责按钮事件 (EDT) 的线程已经在等待。您必须在不同的线程上调用 notify()。

public void actionPerformed(ActionEvent e) {
    synchronized(count) {
        if(e.getSource()==wait) {
            try
            {
                count.wait(); // start blocking this thread
                wait.setEnabled(false); // im pretty sure this doesnt get called until notified either
                notify.setEnabled(true);
            }
            catch (Exception e1) {
                e1.printStackTrace();
            }
        } else if(e.getSource()==notify) {
            count.notify(); // will never get called cause this thread is blocked, waiting to be notified by another thread
            wait.setEnabled(true);
            notify.setEnabled(false);
        }

    }
}