Java - invokeLater 将不会运行

Question

我按照教程创建了一个信使。我正确地输入了代码，并且我对所有内容的作用有相当基本的了解。

尽管如此，我最终并没有得到相同的结果。代码如下:

<小时/>

public class Server extends JFrame{
    private JTextField userText;
    private JTextArea chatWindow;
    private ObjectOutputStream output;
    private ObjectInputStream input; 
    private ServerSocket server;
    private Socket connection;

    //constructor
    public Server(){
        super("Coffee Messenger");
        userText = new JTextField();
        userText.setEditable(false);
        userText.addActionListener(
            new ActionListener(){
                public void actionPerformed(ActionEvent event){
                    sendMessage(event.getActionCommand());
                    userText.setText("");
                }
            }
        );
        add(userText, BorderLayout.SOUTH);
        chatWindow = new JTextArea();
        add(new JScrollPane());
        setSize(300,150);
        setVisible(true);   
    }
    //set up and run the server
    public void startRunning(){
        try{
            server = new ServerSocket(6789, 100);
            while(true){
                try{
                    //connect and have conversation
                    waitForConnection();
                    setupStreams();
                    whileChatting();
                }catch(EOFException eofException){
                    showMessage("\n Server ended the connection!");
                }finally{
                    closeCrap();
                }
            }
        }catch(IOException ioException){
            ioException.printStackTrace();
        }
    }
    //wait for connection, then display connection information
    private void waitForConnection() throws IOException{
        showMessage("Waiting for someone to connect...\n");
        connection = server.accept();
        showMessage("Now connected to " + connection.getInetAddress().getHostName());
    }
    //get stream to send and receive data
    private void setupStreams() throws IOException{
        output = new ObjectOutputStream(connection.getOutputStream());
        output.flush();
        input = new ObjectInputStream(connection.getInputStream());
        showMessage("\n Streams are now setup! \n");
    }
    //during the chat conversation
    private void whileChatting() throws IOException{
        String message = "You are now connected!";
        sendMessage(message);
        ableToType(true);
        do{
            //have conversation
            try{
                message = (String) input.readObject();
                showMessage("\n " + message);
            }catch(ClassNotFoundException classNotFoundException){
                showMessage("\n idk wtf that user sent");
            }
        }while(!message.equals("CLIENT - END"));
    }
    //close streams and sockets (application)
    private void closeCrap(){
        showMessage("\n Closing connections...\n");
        ableToType(false);
        try{
            output.close();
            input.close();
            connection.close();
        }catch(IOException ioException){
            ioException.printStackTrace();
        }
    }
    //send message to client
    private void sendMessage(String message){
        try{
            output.writeObject("SERVER - " + message);
            output.flush();
            showMessage("\nSERVER - " + message);

        }catch(IOException ioException){
            chatWindow.append("\n ERROR: Cannot send message.");
        }
    }
    //updates chatWindow 
    private void showMessage(final String text){
        SwingUtilities.invokeLater(
            new Runnable(){
                public void run(){
                    chatWindow.append(text);
                }
            }
        );
    }
    //sets the ability to edit the textfield
    private void ableToType(final boolean tof){
        SwingUtilities.invokeLater(
            new Runnable(){
                public void run(){
                    userText.setEditable(tof);
                }
            }
        );
    }
}
__

<小时/>

当我从主方法启动应用程序时，字符串“等待某人连接”(来自 waitForConnection 方法)不会显示。我相信问题出在 showMessage 方法中。难道是我用错了？如果我用简单的 system.out.println(); 替换 invokeLater 方法，项目将完全按计划运行。

抱歉，我有点缺乏经验，所以这可能非常简单。预先非常感谢您。

(感谢 thenewboston 制作这些教程)

Answer 1

这里:

chatWindow = new JTextArea();
add(new JScrollPane());

您的 GUI 正在创建一个 JTextArea、chatWindow，但将其添加到没有显示它的内容中，而您的 GUI 显示了一个空的 JScrollPane。如果有就更好了

chatWindow = new JTextArea();
add(new JScrollPane(chatWindow));

这样发送到 JTextArea 的文本就有机会被显示。