java - 线程访问全局变量并强制终止旧线程

Question

一切都在具有给定字段的 GUIActions 类中:

public class GUIActions {
private GUIActions GUI;
private JButton connectButton;
private JTextArea messageArea;

private String IP;
private Integer PORT;
private CommunicationManager comManager;

public static Boolean flag = false;

我有处理连接管理的代码:它启动 comManager 并将标志更改为 true，以便 ThreadManager 知道它必须启动新的 ReceiverThread

class connectButtonActionListener implements ActionListener {

    @Override
    public void actionPerformed(ActionEvent arg0) {
        try {
            comManager = null; //to make sure that old connection is erased
            comManager = new CommunicationManager(IP, PORT);
            flag = true;
            if(!comManager.isAlive()) {
                JOptionPane.showMessageDialog(null, "Can't connect with server \n Server is either unreachable or offline");
            }
        } catch (IOException e) {
            JOptionPane.showMessageDialog(null, "Can't connect with server \n Server is either unreachable or offline");
        }
    }
}

线程代码:

/*
 * @desc Static method that setup GUI including adding tabbed cards into Frame
 * @param -none-
 * @return -none-
 */
public void setupGUI() {
    JFrame frame = new JFrame("Chat Client");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    GUI = new GUIActions();
    GUI.setupCards(frame.getContentPane());

    Thread threadManager = new Thread(new ThreadManager());
    threadManager.start();

    frame.pack();
    frame.setVisible(true);
}

class ThreadManager implements Runnable {
    public void run() {
        while(true) {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("Looking for connection!");
            if(flag == true) {
                System.out.println("Connection found!");
                Thread receiverThread = new Thread(new MessageReceiverRunnable());
                receiverThread.start();
                flag = false;
            }
        }
    }
}

class MessageReceiverRunnable implements Runnable {
    public synchronized void run() {
        System.out.println("Thread running");
        BufferedReader reader;
        String message;
        try {
            if(GUI.comManager==null) {
                System.out.println("comManager null");
                if(GUI.IP == null || GUI.PORT == null) {
                    System.out.println("IP or PORT null");
                }
                comManager = new CommunicationManager(GUI.IP, GUI.PORT);
                reader = comManager.getReader();
            } else {
                System.out.println("comManager NOT null");
                reader = GUI.comManager.getReader();
            }
            while((message = reader.readLine()) != null) {
                GUI.messageArea.append(message + "\n");
            }
        } catch(Exception ex) {
            ex.printStackTrace();
        }
    }
}

因此 ThreadManager 等待连接 (comManager)，如果有连接，它会启动新线程，等待传入消息。我有两个问题:

1)为什么我必须使用 GUI.IP 或 GUI.comManager 而不是 IP 或 comManager 访问 GUIActions 字段？

可运行线程类在 GUIActions 类中!是否与每个线程都有单独的堆栈有关？

2)当有新的receiverThread初始化时，如何强制杀死旧的receiverThread？

干杯!

Answer 1

1. 如果不使用包含它们的对象，您将无法访问类成员变量。这是大多数语言的规则，因为它们不是全局常量，JVM(在这种情况下)不知道您指的是哪些变量。

您能否澄清“可运行线程类在 GUIActions 类中!它与每个线程都有单独的堆栈有关吗？”这个问题？ ？

1. 要终止旧的接收器线程，请将 MessageReceiverRunnable 对象存储在一个变量中并添加一个将退出 run() 方法的标志。创建新的接收器线程时，修改标志以使线程完成。另一种选择是在线程上调用 interrupt() 方法。