Java Swing GUI客户端和服务器聊天应用程序文本区域未更新

我正在使用Java和Swing类为GUI开发一个聊天应用程序

ChatServer类将是从客户端接收消息并回显到所有客户端的服务器，但我只打算为2个客户端进行聊天

ChatClient类是两个客户端。它们在文本区域显示从服务器发送的内容。并将文本字段中的文本发送到服务器

聊天客户端类

package chatclient;

import java.net.Socket;
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.InputStreamReader;

public class ChatClient extends javax.swing.JFrame {


public ChatClient() {
    initComponents();
}

/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {

    scrollPane = new javax.swing.JScrollPane();
    textArea = new javax.swing.JTextArea();
    btnConnect = new javax.swing.JButton();
    btnDisconnect = new javax.swing.JButton();
    lblStatus = new javax.swing.JLabel();
    lblShowStatus = new javax.swing.JLabel();
    txtInput = new javax.swing.JTextField();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
    setTitle("Chat Client A");

    textArea.setEditable(false);
    textArea.setColumns(20);
    textArea.setRows(5);
    textArea.setText("Welcome to the Chat Server. Type '/close' or Click 'Disconnect' to close.");
    textArea.setWrapStyleWord(true);
    textArea.setCaretPosition(textArea.getDocument().getLength());
    scrollPane.setViewportView(textArea);

    btnConnect.setText("Connect");
    btnConnect.setActionCommand("btnConnect");
    btnConnect.addMouseListener(new java.awt.event.MouseAdapter() {
        public void mouseClicked(java.awt.event.MouseEvent evt) {
            btnConnectMouseClicked(evt);
        }
    });

    btnDisconnect.setText("Disconnect");
    btnDisconnect.setActionCommand("btnDisconnect");
    btnDisconnect.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnDisconnectActionPerformed(evt);
        }
    });

    lblStatus.setText("Status: ");

    lblShowStatus.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
    lblShowStatus.setForeground(new java.awt.Color(255, 51, 51));
    lblShowStatus.setText("Disconnected");

    txtInput.setToolTipText("");
    txtInput.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            txtInputActionPerformed(evt);
        }
    });

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addComponent(scrollPane)
                .addGroup(layout.createSequentialGroup()
                    .addComponent(btnConnect)
                    .addGap(18, 18, 18)
                    .addComponent(btnDisconnect)
                    .addGap(42, 42, 42)
                    .addComponent(lblStatus)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                    .addComponent(lblShowStatus)
                    .addGap(0, 42, Short.MAX_VALUE))
                .addComponent(txtInput))
            .addContainerGap())
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addComponent(scrollPane, javax.swing.GroupLayout.PREFERRED_SIZE, 213, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 11, Short.MAX_VALUE)
            .addComponent(txtInput, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(btnConnect)
                .addComponent(btnDisconnect)
                .addComponent(lblStatus)
                .addComponent(lblShowStatus))
            .addContainerGap())
    );

    pack();
}// </editor-fold>                        

private void btnConnectMouseClicked(java.awt.event.MouseEvent evt) {                                        
    // TODO add your handling code here:
    lblShowStatus.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
    lblShowStatus.setForeground(new java.awt.Color(0, 204, 51));
    lblShowStatus.setText("Connected");

    // ADD CODES FOR CONNECTING TO CHAT SERVER

}                                       

private void btnDisconnectActionPerformed(java.awt.event.ActionEvent evt) {                                              
    // TODO add your handling code here:
    lblShowStatus.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
    lblShowStatus.setForeground(new java.awt.Color(255, 51, 51));
    lblShowStatus.setText("Disconnected");

    // ADD CODES FOR DISCONNECTING FROM CHAT SERVER

}                                             

private void txtInputActionPerformed(java.awt.event.ActionEvent evt) {                                         
    // TODO add your handling code here:
}                                        

/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    try {
        for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(ChatClient.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(ChatClient.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(ChatClient.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(ChatClient.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>      

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new ChatClient().setVisible(true);
        }
    });

    String input = "", serverInput = "";
    String host = "localhost";
    int port = 1337;
    Socket client;

    // updateTextArea("TEST UPDATE");

    try {
        client = new Socket(host, port);
        System.out.println("Connected to Server!");

        DataInputStream in = new DataInputStream(client.getInputStream());
        DataOutputStream out = new DataOutputStream(client.getOutputStream());

        System.out.println("Before setting text area");
        updateTextArea("trying to update");

        do {
            // HANDLE INPUT PART HERE
            serverInput = in.readUTF();


            if(serverInput != null) {
                System.out.println("Reached here");
                System.out.println(serverInput);
                updateTextArea(serverInput); 
            }

        } while(!input.equals("/close"));
        System.out.println("Program closed");
    }    

    catch(Exception exc) {
        System.err.println(exc.getMessage());
    }


}

private static void updateTextArea(String temp) {
    textArea.setText(textArea.getText() + "\n" + temp + "\n");
    textArea.setCaretPosition(textArea.getDocument().getLength());
}

// Variables declaration - do not modify                     
private javax.swing.JButton btnConnect;
private javax.swing.JButton btnDisconnect;
private javax.swing.JLabel lblShowStatus;
private javax.swing.JLabel lblStatus;
private javax.swing.JScrollPane scrollPane;
private static javax.swing.JTextArea textArea;
private javax.swing.JTextField txtInput;
// End of variables declaration                   
}

package chatserver;

import java.io.BufferedReader;
import java.io.InputStreamReader;
// for testing
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.net.ServerSocket;
import java.net.Socket;

/**
 *
 * @author wacats
 */
public class ChatServer {
public static void main(String args[]) {
    int port = 1337;

    try {
        ServerSocket server = new ServerSocket(port);
        String inMessage = "";

        while(true) {
            Socket clientA = server.accept();
            DataInputStream inA = new DataInputStream(clientA.getInputStream());
            DataOutputStream outA = new DataOutputStream(clientA.getOutputStream());
            // outA.writeUTF("Welcome to the Chat Server. Type '/close' or Click 'Disconnect' to close.");

            // for testing
            // BufferedReader user = new BufferedReader(new InputStreamReader(System.in));

            do {
                inMessage = inA.readUTF();

                outA.writeUTF("testing");

                if(inMessage != null) {
                   outA.writeUTF(inMessage); 
                }

            } while(!inMessage.equals("/close"));
            clientA.close();
        }



    }

    catch(Exception ex) {
        ex.printStackTrace();
    }
}
}

我对这个项目的过程的想法是：

启动聊天服务器

启动聊天客户端

当两个客户端都连接到服务器时，他们就可以开始聊天了

按“回车”键将文本字段中的文本发送到服务器

服务器将向两个客户端广播文本

客户端将更新附加从服务器接收的文本的文本区域

---

基本问题是，

textArea

在您尝试调用

updateTextArea

时是

null

，这是因为

invokeLater

调用尚未执行并构建您的UI，您基本上有竞争条件

处理Swing中的

Socket

s的正常方法是使用

SwingWorker

查看和了解更多详细信息

有很多方法可以解决你的问题。您可以使用

SwingWorker

从套接字读取文本并生成更新通知（通过

publish

/

过程

）方法，这通常被称为“观察者模式”。这很好，因为它将代码解耦，并生成一个更可重用的解决方案

SocketReader

这个类所做的就是从

Socket

读取文本，并从文本生成

ActionEvent

s，很简单

public class SocketReader extends SwingWorker<Void, String> {

    private List<ActionListener> actionListeners;

    public SocketReader() {
        actionListeners = new ArrayList<>(25);
    }

    public void addActionListener(ActionListener listener) {
        actionListeners.add(listener);
    }

    public void removeActionListener(ActionListener listener) {
        actionListeners.remove(listener);
    }

    @Override
    protected Void doInBackground() throws Exception {
        System.out.println("Connected to Server!");

        try (DataInputStream in = new DataInputStream(SocketManager.INSTACNE.getInputStream())) {

            System.out.println("Before setting text area");

            String serverInput = null;
            do {
                // HANDLE INPUT PART HERE
                serverInput = in.readUTF();

                if (serverInput != null) {
                    System.out.println("Read " + serverInput);
                    publish(serverInput);
                }

            } while (!serverInput.equals("/close"));
            System.out.println("Program closed");
        }
        return null;
    }

    @Override
    protected void process(List<String> chunks) {
        for (String text : chunks) {
            ActionEvent evt = new ActionEvent(this, ActionEvent.ACTION_PERFORMED, text);
            for (ActionListener listener : actionListeners) {
                listener.actionPerformed(evt);
            }
        }
    }

}

SocketManager

好吧，这对我来说有点过分了，但是我想要一个用于

套接字的中央控制器，你不必使用单例，你可以简单地将它变成一个简单的类，并将它的引用传递给你的
聊天客户端
，然后向下传递给
SocketReader/Writer
，但是它很晚了，我很懒

public enum SocketManager {
    INSTACNE;

    private String host = "localhost";
    private int port = 1337;
    private Socket socket;

    public Socket open() throws IOException {
        if (socket != null) {
            close();
        }
        socket = new Socket(host, port);
        return socket;
    }

    public void close() throws IOException {
        if (socket == null) {
            return;
        }
        socket.close();
    }

    public boolean isOpen() {
        return socket != null
            && socket.isConnected()
            && !socket.isClosed()
            && !socket.isInputShutdown()
            && !socket.isOutputShutdown();
    }

    public InputStream getInputStream() throws IOException {
        Objects.requireNonNull(socket, "Socket is not open");
        return socket.getInputStream();
    }

    public OutputStream getOutputStream() throws IOException {
        Objects.requireNonNull(socket, "Socket is not open");
        return socket.getOutputStream();
    }
}

ChatClient
这很好，非常棒，但是你打算怎么用呢

基本上，您将在
ChatClient
中创建
SocketReader
和
SocketWriter
的实例，将
ActionListener
附加到读取器，并在触发时更新
JTextArea
，并将您想要发送的文本发送到
SocketWriter
，例如

public class ChatClient extends javax.swing.JFrame {

    public ChatClient() {
        initComponents();
        socketReader = new SocketReader();
        socketReader.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                String text = e.getActionCommand();
                textArea.append(text);
                textArea.append("\n");
                textArea.setCaretPosition(textArea.getDocument().getLength());
            }
        });
        socketReader.execute();

        socketWriter = new SocketWriter();
        socketWriter.execute();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        scrollPane = new javax.swing.JScrollPane();
        textArea = new javax.swing.JTextArea();
        btnConnect = new javax.swing.JButton();
        btnDisconnect = new javax.swing.JButton();
        lblStatus = new javax.swing.JLabel();
        lblShowStatus = new javax.swing.JLabel();
        txtInput = new javax.swing.JTextField();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("Chat Client A");

        textArea.setEditable(false);
        textArea.setColumns(20);
        textArea.setRows(5);
        textArea.setText("Welcome to the Chat Server. Type '/close' or Click 'Disconnect' to close.");
        textArea.setWrapStyleWord(true);
        textArea.setCaretPosition(textArea.getDocument().getLength());
        scrollPane.setViewportView(textArea);

        btnConnect.setText("Connect");
        btnConnect.setActionCommand("btnConnect");
        btnConnect.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseClicked(java.awt.event.MouseEvent evt) {
                btnConnectMouseClicked(evt);
            }
        });

        btnDisconnect.setText("Disconnect");
        btnDisconnect.setActionCommand("btnDisconnect");
        btnDisconnect.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnDisconnectActionPerformed(evt);
            }
        });

        lblStatus.setText("Status: ");

        lblShowStatus.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
        lblShowStatus.setForeground(new java.awt.Color(255, 51, 51));
        lblShowStatus.setText("Disconnected");

        txtInput.setToolTipText("");
        txtInput.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                txtInputActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(scrollPane)
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(btnConnect)
                        .addGap(18, 18, 18)
                        .addComponent(btnDisconnect)
                        .addGap(42, 42, 42)
                        .addComponent(lblStatus)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addComponent(lblShowStatus)
                        .addGap(0, 42, Short.MAX_VALUE))
                    .addComponent(txtInput))
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(scrollPane, javax.swing.GroupLayout.PREFERRED_SIZE, 213, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 11, Short.MAX_VALUE)
                .addComponent(txtInput, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(btnConnect)
                    .addComponent(btnDisconnect)
                    .addComponent(lblStatus)
                    .addComponent(lblShowStatus))
                .addContainerGap())
        );

        pack();
    }// </editor-fold>                        

    private void btnConnectMouseClicked(java.awt.event.MouseEvent evt) {
        // TODO add your handling code here:
        lblShowStatus.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
        lblShowStatus.setForeground(new java.awt.Color(0, 204, 51));
        lblShowStatus.setText("Connected");

        // ADD CODES FOR CONNECTING TO CHAT SERVER
    }

    private void btnDisconnectActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
        lblShowStatus.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
        lblShowStatus.setForeground(new java.awt.Color(255, 51, 51));
        lblShowStatus.setText("Disconnected");

        // ADD CODES FOR DISCONNECTING FROM CHAT SERVER
    }

    private void txtInputActionPerformed(java.awt.event.ActionEvent evt) {
        if (SocketManager.INSTACNE.isOpen()) {
            socketWriter.write(txtInput.getText());
        } else {
            System.out.println("!! Not open");
        }
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {

        try {
            /* Set the Nimbus look and feel */
            //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
            /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
            * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
             */
            try {
                for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                    if ("Nimbus".equals(info.getName())) {
                        javax.swing.UIManager.setLookAndFeel(info.getClassName());
                        break;
                    }
                }
            } catch (ClassNotFoundException ex) {
                java.util.logging.Logger.getLogger(ChatClient.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            } catch (InstantiationException ex) {
                java.util.logging.Logger.getLogger(ChatClient.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            } catch (IllegalAccessException ex) {
                java.util.logging.Logger.getLogger(ChatClient.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            } catch (javax.swing.UnsupportedLookAndFeelException ex) {
                java.util.logging.Logger.getLogger(ChatClient.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            }
            //</editor-fold>

            SocketManager.INSTACNE.open();

            /* Create and display the form */
            java.awt.EventQueue.invokeLater(new Runnable() {
                public void run() {
                    new ChatClient().setVisible(true);
                }
            });

        } catch (IOException ex) {
            ex.printStackTrace();
        }
        //</editor-fold>      

    }

    private SocketWriter socketWriter;
    private SocketReader socketReader;

    // Variables declaration - do not modify                     
    private javax.swing.JButton btnConnect;
    private javax.swing.JButton btnDisconnect;
    private javax.swing.JLabel lblShowStatus;
    private javax.swing.JLabel lblStatus;
    private javax.swing.JScrollPane scrollPane;
    private javax.swing.JTextArea textArea;
    private javax.swing.JTextField txtInput;
    // End of variables declaration                   
}

通常，当客户端连接时，您会启动一个新的
线程
，并让它处理客户端
套接字
，但这不是我的重点

因此，基于所有这些，你有很多阅读需要跟上，包括和
基本问题是，
textArea
是
null
当你尝试调用
updateTextArea
，这是因为
invokeLater
调用还没有执行并构建你的UI，你基本上有一个竞争条件

处理Swing中的
Socket
s的正常方法是使用
SwingWorker

查看和了解更多详细信息

有很多方法可以解决你的问题。您可以使用
SwingWorker
从套接字读取文本并生成更新通知（通过
publish
/
过程
）方法，这通常被称为“观察者模式”。这很好，因为它将代码解耦，并生成一个更可重用的解决方案

SocketReader
这个类所做的就是从
Socket
读取文本，并从文本生成
ActionEvent
s，很简单

public class SocketReader extends SwingWorker<Void, String> {

    private List<ActionListener> actionListeners;

    public SocketReader() {
        actionListeners = new ArrayList<>(25);
    }

    public void addActionListener(ActionListener listener) {
        actionListeners.add(listener);
    }

    public void removeActionListener(ActionListener listener) {
        actionListeners.remove(listener);
    }

    @Override
    protected Void doInBackground() throws Exception {
        System.out.println("Connected to Server!");

        try (DataInputStream in = new DataInputStream(SocketManager.INSTACNE.getInputStream())) {

            System.out.println("Before setting text area");

            String serverInput = null;
            do {
                // HANDLE INPUT PART HERE
                serverInput = in.readUTF();

                if (serverInput != null) {
                    System.out.println("Read " + serverInput);
                    publish(serverInput);
                }

            } while (!serverInput.equals("/close"));
            System.out.println("Program closed");
        }
        return null;
    }

    @Override
    protected void process(List<String> chunks) {
        for (String text : chunks) {
            ActionEvent evt = new ActionEvent(this, ActionEvent.ACTION_PERFORMED, text);
            for (ActionListener listener : actionListeners) {
                listener.actionPerformed(evt);
            }
        }
    }

}

SocketManager
好吧，这对我来说有点过分了，但是我想要一个用于
套接字的中央控制器，你不必使用单例，你可以简单地将它变成一个简单的类，并将它的引用传递给你的
聊天客户端
，然后向下传递给
SocketReader/Writer
，但是它很晚了，我很懒

public enum SocketManager {
    INSTACNE;

    private String host = "localhost";
    private int port = 1337;
    private Socket socket;

    public Socket open() throws IOException {
        if (socket != null) {
            close();
        }
        socket = new Socket(host, port);
        return socket;
    }

    public void close() throws IOException {
        if (socket == null) {
            return;
        }
        socket.close();
    }

    public boolean isOpen() {
        return socket != null
            && socket.isConnected()
            && !socket.isClosed()
            && !socket.isInputShutdown()
            && !socket.isOutputShutdown();
    }

    public InputStream getInputStream() throws IOException {
        Objects.requireNonNull(socket, "Socket is not open");
        return socket.getInputStream();
    }

    public OutputStream getOutputStream() throws IOException {
        Objects.requireNonNull(socket, "Socket is not open");
        return socket.getOutputStream();
    }
}

ChatClient
这很好，非常棒，但是你打算怎么用呢

基本上，您将在
ChatClient
中创建
SocketReader
和
SocketWriter
的实例，将
ActionListener
附加到读取器，并在触发时更新
JTextArea
，并将您想要发送的文本发送到
SocketWriter
，例如

public class ChatClient extends javax.swing.JFrame {

    public ChatClient() {
        initComponents();
        socketReader = new SocketReader();
        socketReader.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                String text = e.getActionCommand();
                textArea.append(text);
                textArea.append("\n");
                textArea.setCaretPosition(textArea.getDocument().getLength());
            }
        });
        socketReader.execute();

        socketWriter = new SocketWriter();
        socketWriter.execute();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        scrollPane = new javax.swing.JScrollPane();
        textArea = new javax.swing.JTextArea();
        btnConnect = new javax.swing.JButton();
        btnDisconnect = new javax.swing.JButton();
        lblStatus = new javax.swing.JLabel();
        lblShowStatus = new javax.swing.JLabel();
        txtInput = new javax.swing.JTextField();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("Chat Client A");

        textArea.setEditable(false);
        textArea.setColumns(20);
        textArea.setRows(5);
        textArea.setText("Welcome to the Chat Server. Type '/close' or Click 'Disconnect' to close.");
        textArea.setWrapStyleWord(true);
        textArea.setCaretPosition(textArea.getDocument().getLength());
        scrollPane.setViewportView(textArea);

        btnConnect.setText("Connect");
        btnConnect.setActionCommand("btnConnect");
        btnConnect.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseClicked(java.awt.event.MouseEvent evt) {
                btnConnectMouseClicked(evt);
            }
        });

        btnDisconnect.setText("Disconnect");
        btnDisconnect.setActionCommand("btnDisconnect");
        btnDisconnect.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btnDisconnectActionPerformed(evt);
            }
        });

        lblStatus.setText("Status: ");

        lblShowStatus.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
        lblShowStatus.setForeground(new java.awt.Color(255, 51, 51));
        lblShowStatus.setText("Disconnected");

        txtInput.setToolTipText("");
        txtInput.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                txtInputActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(scrollPane)
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(btnConnect)
                        .addGap(18, 18, 18)
                        .addComponent(btnDisconnect)
                        .addGap(42, 42, 42)
                        .addComponent(lblStatus)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addComponent(lblShowStatus)
                        .addGap(0, 42, Short.MAX_VALUE))
                    .addComponent(txtInput))
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(scrollPane, javax.swing.GroupLayout.PREFERRED_SIZE, 213, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 11, Short.MAX_VALUE)
                .addComponent(txtInput, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(btnConnect)
                    .addComponent(btnDisconnect)
                    .addComponent(lblStatus)
                    .addComponent(lblShowStatus))
                .addContainerGap())
        );

        pack();
    }// </editor-fold>                        

    private void btnConnectMouseClicked(java.awt.event.MouseEvent evt) {
        // TODO add your handling code here:
        lblShowStatus.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
        lblShowStatus.setForeground(new java.awt.Color(0, 204, 51));
        lblShowStatus.setText("Connected");

        // ADD CODES FOR CONNECTING TO CHAT SERVER
    }

    private void btnDisconnectActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
        lblShowStatus.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N
        lblShowStatus.setForeground(new java.awt.Color(255, 51, 51));
        lblShowStatus.setText("Disconnected");

        // ADD CODES FOR DISCONNECTING FROM CHAT SERVER
    }

    private void txtInputActionPerformed(java.awt.event.ActionEvent evt) {
        if (SocketManager.INSTACNE.isOpen()) {
            socketWriter.write(txtInput.getText());
        } else {
            System.out.println("!! Not open");
        }
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {

        try {
            /* Set the Nimbus look and feel */
            //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
            /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
            * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
             */
            try {
                for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                    if ("Nimbus".equals(info.getName())) {
                        javax.swing.UIManager.setLookAndFeel(info.getClassName());
                        break;
                    }
                }
            } catch (ClassNotFoundException ex) {
                java.util.logging.Logger.getLogger(ChatClient.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            } catch (InstantiationException ex) {
                java.util.logging.Logger.getLogger(ChatClient.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            } catch (IllegalAccessException ex) {
                java.util.logging.Logger.getLogger(ChatClient.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            } catch (javax.swing.UnsupportedLookAndFeelException ex) {
                java.util.logging.Logger.getLogger(ChatClient.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
            }
            //</editor-fold>

            SocketManager.INSTACNE.open();

            /* Create and display the form */
            java.awt.EventQueue.invokeLater(new Runnable() {
                public void run() {
                    new ChatClient().setVisible(true);
                }
            });

        } catch (IOException ex) {
            ex.printStackTrace();
        }
        //</editor-fold>      

    }

    private SocketWriter socketWriter;
    private SocketReader socketReader;

    // Variables declaration - do not modify                     
    private javax.swing.JButton btnConnect;
    private javax.swing.JButton btnDisconnect;
    private javax.swing.JLabel lblShowStatus;
    private javax.swing.JLabel lblStatus;
    private javax.swing.JScrollPane scrollPane;
    private javax.swing.JTextArea textArea;
    private javax.swing.JTextField txtInput;
    // End of variables declaration                   
}

通常，当客户端连接时，您会启动一个新的
线程
，并让它处理客户端
套接字
，但这不是我的重点

因此，基于所有这些，您有很多阅读需要跟上，包括和
您需要更新Swing线程中的文本区域。您可能需要调用由方法
SwingUtilities.invokeLater
包装的方法
updateextarea
和void
static
引用；使用
append
over
setText
您的
updateextarea
中有
NullPointerException
，因为在UI建立之前，允许从服务器读取/写入内容的循环运行change
System.err.println（exc.getMessage（））至
exc.printStackTrace（）您将看到why@MadProgrammer如何在不使用static的情况下访问文本区域？您需要在Swing线程中更新文本区域。您可能需要调用由方法
SwingUtilities.invokeLater
包装的方法
updateextarea
和void
static
引用；使用
append
over
setText
您的
updateextarea
中有
NullPointerException
，因为在UI建立之前允许从服务器读/写内容的循环运行change
System.err.println（exc.getMessage（））