Simple chat room Swing GUI

Question

I need somebody to review and polish my GUI code for my very very simple chat client. I haven't built any of the server sockets, so I'll do that later, but for now I just want people to tell me how crap my code is and how I can make it better. I'll post the full code below, but keep in mind that it is built to be as simple as possible and that some of it (like the stupid username system) could be temporary.

Something I want to know is how I would get the messageBox to extend the whole screen up to the button. If you full screen your window, you'll see what I mean.

MainGUI:

package coltGUI;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Font;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.UIManager;

public class MainGUI {

    MainGUI mainGUI;
    JFrame newFrame = new JFrame("Colt Chat v0.1");
    JButton sendMessage;
    JTextField messageBox;
    JTextArea chatBox;
    JTextField usernameChooser;
    JFrame preFrame;

    public static void main(String[] args) {
        try {
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        } catch (Exception e) {
            e.printStackTrace();
        }
        MainGUI mainGUI = new MainGUI();
        mainGUI.preDisplay();
    }


    public void preDisplay() {
        newFrame.setVisible(false);
        preFrame = new JFrame("Choose your username!(Colt chat v0.1");
        usernameChooser = new JTextField();
        JLabel chooseUsernameLabel = new JLabel("Pick a username:");
        JButton enterServer = new JButton("Enter Chat Server");
        JPanel prePanel = new JPanel(new GridBagLayout());

        GridBagConstraints preRight = new GridBagConstraints();
        preRight.anchor = GridBagConstraints.EAST;
        GridBagConstraints preLeft = new GridBagConstraints();
        preLeft.anchor = GridBagConstraints.WEST;
        preRight.weightx = 2.0;
        preRight.fill = GridBagConstraints.HORIZONTAL;
        preRight.gridwidth = GridBagConstraints.REMAINDER;

        prePanel.add(chooseUsernameLabel, preLeft);
        prePanel.add(usernameChooser, preRight);
        preFrame.add(BorderLayout.CENTER, prePanel);
        preFrame.add(BorderLayout.SOUTH, enterServer);
        preFrame.setVisible(true);
        preFrame.setSize(300, 300);

        enterServer.addActionListener(new enterServerButtonListener());
    }

    public void display() {
        newFrame.setVisible(true);
        JPanel southPanel = new JPanel();
        newFrame.add(BorderLayout.SOUTH, southPanel);
        southPanel.setBackground(Color.BLUE);
        southPanel.setLayout(new GridBagLayout());

        messageBox = new JTextField(30);
        sendMessage = new JButton("Send Message");
        chatBox = new JTextArea();
        chatBox.setEditable(false);
        newFrame.add(new JScrollPane(chatBox), BorderLayout.CENTER);

        chatBox.setLineWrap(true);

        GridBagConstraints left = new GridBagConstraints();
        left.anchor = GridBagConstraints.WEST;
        GridBagConstraints right = new GridBagConstraints();
        right.anchor = GridBagConstraints.EAST;
        right.weightx = 2.0;

        southPanel.add(messageBox, left);
        southPanel.add(sendMessage, right);

        chatBox.setFont(new Font("Serif", Font.PLAIN, 15));
        sendMessage.addActionListener(new sendMessageButtonListener());
        newFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        newFrame.setSize(470, 300);
    }

    class sendMessageButtonListener implements ActionListener {
        public void actionPerformed(ActionEvent event) {
            if (messageBox.getText().length() < 1) {
                // do nothing 
            } else if (messageBox.getText().equals(".clear")) {
                chatBox.setText("Cleared all messages\n");
                messageBox.setText("");
            } else {
                chatBox.append("<" + username + ">:  " + messageBox.getText() + "\n");
                messageBox.setText("");
            }
        }
    }

    String username;

    class enterServerButtonListener implements ActionListener {
        public void actionPerformed(ActionEvent event) {
            username = usernameChooser.getText();
            if (username.length() < 1) {System.out.println("No!"); }
            else {
            preFrame.setVisible(false);
            display();
            }
        }

    }
}

Answer 1

Your code was mostly good. Starting from the top of the program and working down, I'll list my changes.

• I added a global string with the application name, since you used it in more than one place. Now, you only have one string to change when you want to change the version number.

• I put the Swing GUI code in the Event Dispatch thread (EDT) in the main method.

• In the preDisplay method, I added some insets to make the display look nicer. I moved the setVisible method to the end.

• In the display method, I added a main JPanel. I added an anchor and fill, as well as weights, to the left and right GridBagConstants. I added weights, which is the first time I've had to do so in a GridBagLayout. I was amazed at how much weight I had to give the left GBC to make the field fill my 22" monitor. I rearranged lines to group the component method calls together. I find that makes troubleshooting easier.

• I added a focus method call to the messageBox so that the cursor would stay there to make typing easier for the user. For some reason, I couldn't get the messageBox focus when the JFrame first comes up.

package coltGUI;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Font;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;

public class MainGUI {

    String      appName     = "Colt Chat v0.1";
    MainGUI     mainGUI;
    JFrame      newFrame    = new JFrame(appName);
    JButton     sendMessage;
    JTextField  messageBox;
    JTextArea   chatBox;
    JTextField  usernameChooser;
    JFrame      preFrame;

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager
                            .getSystemLookAndFeelClassName());
                } catch (Exception e) {
                    e.printStackTrace();
                }
                MainGUI mainGUI = new MainGUI();
                mainGUI.preDisplay();
            }
        });
    }

    public void preDisplay() {
        newFrame.setVisible(false);
        preFrame = new JFrame(appName);
        usernameChooser = new JTextField(15);
        JLabel chooseUsernameLabel = new JLabel("Pick a username:");
        JButton enterServer = new JButton("Enter Chat Server");
        enterServer.addActionListener(new enterServerButtonListener());
        JPanel prePanel = new JPanel(new GridBagLayout());

        GridBagConstraints preRight = new GridBagConstraints();
        preRight.insets = new Insets(0, 0, 0, 10);
        preRight.anchor = GridBagConstraints.EAST;
        GridBagConstraints preLeft = new GridBagConstraints();
        preLeft.anchor = GridBagConstraints.WEST;
        preLeft.insets = new Insets(0, 10, 0, 10);
        // preRight.weightx = 2.0;
        preRight.fill = GridBagConstraints.HORIZONTAL;
        preRight.gridwidth = GridBagConstraints.REMAINDER;

        prePanel.add(chooseUsernameLabel, preLeft);
        prePanel.add(usernameChooser, preRight);
        preFrame.add(prePanel, BorderLayout.CENTER);
        preFrame.add(enterServer, BorderLayout.SOUTH);
        preFrame.setSize(300, 300);
        preFrame.setVisible(true);

    }

    public void display() {
        JPanel mainPanel = new JPanel();
        mainPanel.setLayout(new BorderLayout());

        JPanel southPanel = new JPanel();
        southPanel.setBackground(Color.BLUE);
        southPanel.setLayout(new GridBagLayout());

        messageBox = new JTextField(30);
        messageBox.requestFocusInWindow();

        sendMessage = new JButton("Send Message");
        sendMessage.addActionListener(new sendMessageButtonListener());

        chatBox = new JTextArea();
        chatBox.setEditable(false);
        chatBox.setFont(new Font("Serif", Font.PLAIN, 15));
        chatBox.setLineWrap(true);

        mainPanel.add(new JScrollPane(chatBox), BorderLayout.CENTER);

        GridBagConstraints left = new GridBagConstraints();
        left.anchor = GridBagConstraints.LINE_START;
        left.fill = GridBagConstraints.HORIZONTAL;
        left.weightx = 512.0D;
        left.weighty = 1.0D;

        GridBagConstraints right = new GridBagConstraints();
        right.insets = new Insets(0, 10, 0, 0);
        right.anchor = GridBagConstraints.LINE_END;
        right.fill = GridBagConstraints.NONE;
        right.weightx = 1.0D;
        right.weighty = 1.0D;

        southPanel.add(messageBox, left);
        southPanel.add(sendMessage, right);

        mainPanel.add(BorderLayout.SOUTH, southPanel);

        newFrame.add(mainPanel);
        newFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        newFrame.setSize(470, 300);
        newFrame.setVisible(true);
    }

    class sendMessageButtonListener implements ActionListener {
        public void actionPerformed(ActionEvent event) {
            if (messageBox.getText().length() < 1) {
                // do nothing
            } else if (messageBox.getText().equals(".clear")) {
                chatBox.setText("Cleared all messages\n");
                messageBox.setText("");
            } else {
                chatBox.append("<" + username + ">:  " + messageBox.getText()
                        + "\n");
                messageBox.setText("");
            }
            messageBox.requestFocusInWindow();
        }
    }

    String  username;

    class enterServerButtonListener implements ActionListener {
        public void actionPerformed(ActionEvent event) {
            username = usernameChooser.getText();
            if (username.length() < 1) {
                System.out.println("No!");
            } else {
                preFrame.setVisible(false);
                display();
            }
        }

    }
}