Java JFrame 中的所有内容均不可见

Question

I made a messaging program where the client has a GUI. Before starting the client the client program needs info about the user and the server. I entered the info through the command line using the args array.

But now that I got the program working I made a GUI for entering the info. I made it in another class that calls the client class and passes the info to the client class. The info GUI works fine but when I enter the info and call the client class the frame shows up but none of the components are visible in the frame.

When I revert to back to the old method the client GUI works fine. I don't know what else I should do.

The code that calls the client class:

btn.addActionListener(new ActionListener() {
    ...
    username = Username.getText();
    hostName = sa.getText();
    portNr = Integer.parseInt(spnr.getText());
    f.dispose();
    System.out.println("frame disposed of");
    try {
        Client client = new Client();
        f.dispose();
        Client.llc(username, hostName, portNr);
    } catch (IOException e) {
        e.printStackTrace();
    }
    }
});

The client code:

public static void llc(String iun, String ihn, int ipnr) throws IOException {
        username = iun;
        hostName = ihn;
        portNr = ipnr;
        launchClient();
    }

    public static void launchClient() throws IOException {
        try (
            //socket setup
            Socket socket = new Socket(hostName, portNr);
            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        ) {
            System.out.println("opened streams");

            //frame setup
            JFrame frame = new JFrame("frame");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

            //text field
            JTextField MSGText = new JTextField(5);

            //text area
            JTextArea MSGD = new JTextArea(20, 30);
            MSGD.setEditable(false);
            JScrollPane scrollPane = new JScrollPane(MSGD);
            System.out.println("opened streams");

            //button
            JButton b = new JButton("Send message");
            b.setPreferredSize(new Dimension(60, 30));
            b.addActionListener(new ActionListener() {

                public void actionPerformed(ActionEvent event) {
                    sendMSG = MSGText.getText();
                    MSGText.setText("");
                    out.println("<" + username + ">: " + sendMSG);
                }
            });

            //panel
            JPanel p = new JPanel();
            p.setLayout(new BoxLayout(p, BoxLayout.PAGE_AXIS));
            p.add(Box.createVerticalStrut(5));
            p.add(scrollPane);
            p.add(Box.createVerticalStrut(5));
            p.add(MSGText);
            p.add(Box.createVerticalStrut(5));
            p.add(b);
            p.add(Box.createVerticalStrut(5));

            JPanel pMain = new JPanel();
            pMain.setLayout(new BoxLayout(pMain, BoxLayout.LINE_AXIS));
            pMain.add(Box.createHorizontalStrut(5));
            pMain.add(p);
            pMain.add(Box.createHorizontalStrut(5));
            frame.getContentPane().add(pMain);

            //frame visiblity
            frame.pack();
            frame.setVisible(true);
            System.out.println("opened streams");

            while((getMSG = in.readLine()) != null) {
                MSGD.append(getMSG + "\n");
                System.out.println("opened streams");
            }
        }


    }

Answer 1

If your client code is a Client class that extends JFrame, then it's possible that the Frame is initializing before the components. To fix this, you can just set your JFrame member to public global variable in your client class and then call client.frame.repaint() after you call llc.

public class Client extends JFrame {
    public JFrame frame;
    //everything else the same 
}

-----------------------------------

btn.addActionListener(new ActionListener() {
    ...
    username = Username.getText();
    hostName = sa.getText();
    portNr = Integer.parseInt(spnr.getText());
    f.dispose();
    System.out.println("frame disposed of");
    try {
        Client client = new Client();
        f.dispose();
        Client.llc(username, hostName, portNr);
        client.frame.repaint();
    } catch (IOException e) {
        e.printStackTrace();
    }
    }
});