java - 我无法停止 java SwingWorker 进程

Question

我在 java 中运行一个 tcp 服务器，它是使用 SwingWorker 类完成的。第一次它将成功启动，但是当我停止并启动该过程时，它将无法正常工作。我找不到问题所在，请帮我解决这个问题

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;

public class SwingWorkerDemo extends JFrame {
     /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private static ServerSocket serverSocket;
        private static Socket clientSocket;
        private static InputStreamReader inputStreamReader;
        private static BufferedReader bufferedReader;
        private static String message;

    public SwingWorkerDemo() {
        initialize();
    }

    private void initialize() {
        this.setLayout(new FlowLayout());
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        final JButton startButton = new JButton("Start");
        final JButton stopButton = new JButton("Stop");
        final LongRunProcess process = new LongRunProcess();



        startButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event) {
                try {
                    process.execute();
                } catch (Exception e) {
                    e.printStackTrace();
                }
                startButton.setEnabled(false);
                stopButton.setEnabled(true);
            }
        });

        stopButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
               // JOptionPane.showMessageDialog(null, "Hello There");

process.cancel(true);
startButton.setEnabled(true);
stopButton.setEnabled(false);
            }
        });


        this.getContentPane().add(startButton);
        this.getContentPane().add(stopButton);

        this.pack();
        this.setSize(new Dimension(300, 80));
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new SwingWorkerDemo().setVisible(true);
            }
        });
    }

    class LongRunProcess extends SwingWorker {
        /**
         * @throws Exception
         */
        protected Object doInBackground() throws Exception {
            try {
                serverSocket = new ServerSocket(4545);  //Server socket

            } catch (IOException e) {
                System.out.println("Could not listen on port: 4545");
            }

            System.out.println("Server started. Listening to the port 4545");

            while (true) {
                try {

                    clientSocket = serverSocket.accept();   //accept the client connection
                    inputStreamReader = new InputStreamReader(clientSocket.getInputStream());
                    bufferedReader = new BufferedReader(inputStreamReader); //get the client message
                    message = bufferedReader.readLine();
     if(message.equals("shutdown")){

    Runtime runtime = Runtime.getRuntime();
    Process proc = runtime.exec("shutdown -s -t 00");
    System.exit(0);

     }
     else if(message.equals("restart")){
    Runtime runtime1 = Runtime.getRuntime();
    Process proc2 = runtime1.exec("shutdown -r -t 00");
    System.exit(0);


     }

                    System.out.println(message);
                    inputStreamReader.close();
                    clientSocket.close();

                } catch (IOException ex) {
                    System.out.println("Problem in message reading");
                }
            }

    }
    }
}

Answer 1

根据 SwingWorker#execute() 的 Javadocs

Note: SwingWorker is only designed to be executed once. Executing a SwingWorker more than once will not result in invoking the doInBackground method twice.

因此您看到的行为。所以为了实现你正在寻找的东西。每次按下开始按钮时，您都需要创建 LongRunProcess 的新实例。像这样的东西。

在类级别声明

LongRunProcess process = null;

修改 Action 监听器

 startButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent event) {
            try {
                process = new LongRunProcess();
                process.execute();
            } catch (Exception e) {
                e.printStackTrace();
            }
            startButton.setEnabled(false);
            stopButton.setEnabled(true);
        }
    });

希望这对您有所帮助。