Question

I have a main window with 4 JButtons and an action listener, and three of them call another window and the fourth exits. Two of my windows work fine, but for some reason my window that waits for a client to connect opens and you can see the boundary of the window, but the inside of the window is transparent.
I tried saying new HostWindow() from my main class, and that worked fine; it’s just when I call it from my StartWindow class that it doesn’t work.
code:

StartWindow:

public class StartWindow extends JFrame{
private JPanel pane;
private JButton host;
private JButton join;
private JButton comp;
private JButton exit;

public StartWindow()
{
    this.setSize(220, 110);
    this.setTitle("Closed Arena");
    pane = new JPanel();
    this.add(pane);
    host = new JButton("Host Match");
    host.addActionListener(new myButtonListener());
    join = new JButton("Join Match");
    join.addActionListener(new myButtonListener());
    comp = new JButton("Play Computer");
    comp.addActionListener(new myButtonListener());
    exit = new JButton("Exit");
    exit.addActionListener(new myButtonListener());
    pane.add(host);
    pane.add(join);
    pane.add(comp);
    pane.add(exit);
    this.setResizable(false);
    pane.setVisible(true);
    this.setVisible(true);
    this.setDefaultCloseOperation(EXIT_ON_CLOSE);   

    //If I make a new Hostwindow here it displays properly
    //new HostWindow();
}

private class myButtonListener implements ActionListener
{

    @Override
    public void actionPerformed(ActionEvent e) 
    {
        Object source = e.getSource();
        if(source.equals(host))
        {
            close();
            //But here it displays improperly.
            new HostWindow();
        }
        if(source.equals(join))
        {
            close();
            new JoinWindow();
        }
        if(source.equals(comp))
        {
            close();
            new Arena();
        }
        if(source.equals(exit))
        {
            close();
        }
    }   
}
public void close()
{
    this.dispose();
}
}

HostWindow:

private JPanel panel;
private JLabel text;
private JButton stop;
private LabelEditor edit;
private Thread editThread;
private ServerSocket server;
private Socket mySocket;

public HostWindow()
{
    panel = new JPanel();

    text = new JLabel("Waiting for client");
    stop = new JButton("Stop");
    stop.addActionListener(new buttonList());

    panel.add(text);
    panel.add(stop);
    this.add(panel);

    this.setResizable(false);   
    this.setSize(160, 90);
    this.setTitle("Server");

    this.setVisible(true);
    this.setDefaultCloseOperation(EXIT_ON_CLOSE);

    edit = new LabelEditor(text, "Waiting for client", 700);
    editThread = new Thread(edit);
    editThread.start();

    try 
    {
        server = new ServerSocket(4011);
        mySocket = server.accept();
        server.close();
        new Arena(mySocket, true);
    } 
    catch (IOException e) {
        System.out.print("Failed to set up server!");
    }
    editThread.interrupt();
    this.dispose();
}

Edit: HostWindow does extend JFrame, I jsut didn’t copy-paste the heading, but it looks like this:
public class HostWindow extends JFrame {

Edit2: Thank you answerers, it was fixed when I made it so that the serer starts in a separate thread:

if(source.equals(host))
        {
            close();
            HostWindow hoster = new HostWindow();
            Thread hosterThread = new Thread(hoster);
            hosterThread.start();
        }

and in hostwindow:
I moved the server stuff into the run.

public void run() {
    try 
    {
        server = new ServerSocket(4011);
        mySocket = server.accept();
        server.close();
        new Arena(mySocket, true);
    } 
    catch (IOException e) {
        System.out.print("Failed to set up server!");
    }
    editThread.interrupt();
    this.dispose();     
}

Answer 1

The problem here is that you’re performing a long lasting blocking operation inside the UIThread.

Threads are simultanous sequences of commands that run inside a single program (I recommend reading up on Java concurrency ). There is a thread usually refered to as the UIThread that performs drawing of the UI elements and works with their code.

Creating a socket – a connection to a remote host means you’re starting a process that can take several seconds to perform. And this is happening inside the constructor of the UI class, inside the UIThread. Until the connection is established the rest of the code in the constructor cannot run. This is because the connection process is a blocking operation – the code after the socket creation won’t run until the socket creation is finishsed.

So you should move the socket creation to a different thread.