java - 在 Applet 中动态地将字符串从非主线程更新为主线程

Question

我有一个如下所示的 Applet 代码。我在此 Applet 中有一个名为 String randomNumberStr 的字符串，用于显示从套接字服务器检索到的随机数。 显示小程序窗口后，我有一个名为“连接”的按钮。单击此按钮将连接到 Socket 程序并获得一个随机数字符串。

我的问题是，我在这个 Applet 的单独线程 SocketConnectionThread 中运行套接字连接代码，但是，String randomNumberStr 和 repaint 函数在主线程中。

我如何从这个线程 SocketConnectionThread 访问随机数值并将其传递给 main 并重新绘制 Applet 窗口？

public class CobrowseApplet extends Applet implements ActionListener
{
    private static final long serialVersionUID = 1L;
    String titleStr ;
    String randomNumberStr;
    Image sharedImage;
    BufferedImage image;
    private Button connectBtn;
    Socket localSocket;
    PrintWriter out;
    BufferedReader in;
    static Timer timer;
    int delay = 1000;
    int period = 1000;
    DataInputStream inStream;
    PrintStream outStream;
    InputStream input;

    public void init(){
        titleStr = "Welcome";
        randomNumberStr = "";

        connectBtn = new Button("Connect");

        connectBtn.addActionListener(this);
        add(connectBtn);
        connectBtn.setBounds(200, 50, 90, 20);
        connectBtn.setEnabled(true);
        setLayout( null );

        setSize(550, 650);
    }
    public void paint (final Graphics g)
    {
        //super.paint(g);
        int x = getSize().width;
        int c1 = x/2;
        g.drawString(titleStr, c1-100, 20);
        g.drawString(randomNumberStr, c1-100, 80);
        System.out.println("sharedImage" + sharedImage);
        //g.drawImage(sharedImage, 100, 100, this);
        System.out.println("drawImage");
    }

    @Override
    public void actionPerformed(ActionEvent e)
    {
        Thread thr = new Thread(new SocketConnectionThread(randomNumberStr));
        thr.start();


        if ( connectBtn.getLabel()=="Connect" )
        {
            connectBtn.setLabel("");
            connectBtn.setLabel("Disconnect");
        }
        else
        {
            connectBtn.setLabel("");
            connectBtn.setLabel("Connect");
        }
        System.out.println("randomNumberStr: " + randomNumberStr);

        repaint();
    }

}

class SocketConnectionThread implements Runnable {

    String randomStr;

    public SocketConnectionThread(String randomNumberStr) {
        this.randomStr = randomNumberStr;
    }
    @Override
    public void run() {
        // TODO Auto-generated method stub
        try {
            System.out.println("Before Applet socket connection");

            Socket localSocket = new Socket(getLocalIP(), 8080);

            BufferedReader socketReader = new BufferedReader(new InputStreamReader(localSocket.getInputStream()));
            String msgStr = socketReader.readLine();
            System.out.println("Server Message on Client: " + msgStr);

            // IT GETS THE NEW STRING HERE FROM SOCKET. HOW CAN I PUSH TO MAIN?
            randomStr = msgStr;

        } catch (UnknownHostException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
    String getLocalIP () {
        InetAddress inetAddress = null;
        String ipAddress = null;
        try {
            inetAddress = InetAddress.getLocalHost();
            ipAddress = inetAddress.getHostAddress();
        } catch (UnknownHostException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        System.out.println("ipAddress : " + ipAddress);

        return ipAddress;
    }

}

Answer 1

要在 java 中比较对象，请使用 .equals() 方法而不是“==”运算符

替换下面的代码

 if ( connectBtn.getLabel()=="Connect" )

到

  if ( "Connect".equals.(connectBtn.getLabel()))