Thread sleeping and not blocking the GUI

Newbie & Debugging Questions
#1

Hi,
Please help me out with the following :slight_smile:

Situation:
A login screen with only a “connect” button. Clicking the button should make the game connect to a server.
The server is not running, so it should just keep trying to connect (even though it never will) while not blocking the GUI.

Problem:
GUI freezes when I click the button. I have to kill the process with traskmanager.

Code:
This is the Thread that starts when the button is clicked:

    private static class ButtonCallback implements Runnable {
    	Game game;
    	public ButtonCallback(Game game) {
    		this.game = game;
    	}
    	
    	public void run() {
    		game.network.connect("XXX.XXX.XXX.XXX", XXXX); // edited out IP for privacy
    	}
    }

This is the class containing the ‘connect()’ method:

public class Network {
	Game game;
	SocketChannel socketChan;
	
	public Network(Game game) {
		this.game = game;
		socketChan = null;
	}
	
	public void connect(String server, int port) {
		game.loginGui.lblStatus.setText("Connecting to: " + server + ":" + Integer.toString(port));
		try {
			socketChan = SocketChannel.open();
			socketChan.configureBlocking(false);
			socketChan.connect(new InetSocketAddress(server, port));
			while (socketChan.isConnectionPending()) {
				try {
					Thread.sleep(10);
				} catch (InterruptedException e) {}
			}
			game.loginGui.lblStatus.setText("Connected.");
		} catch (UnknownHostException e) {
			game.loginGui.lblStatus.setText("ERROR: Unknown host");
			e.printStackTrace();
		} catch (IOException e) {
			game.loginGui.lblStatus.setText("ERROR: Failed to connect!");
			e.printStackTrace();
		}
	}
}

I thought the Thread.sleep would make sure the GUI keeps working. Why doesn’t it?

Additional info:
Using LWJGL and TWL
Java eclipse
Windows 7

#2

You will need the work performed in a different thread than the GUI.
This link should help http://java.sun.com/products/jfc/tsc/articles/threads/threads2.html

#3

Yes, but isn’t that what I’m doing by implementing runnable?

#4

Implementing Runnable is necessary but not sufficient. I don’t see any reference of ButtonCallback in the main code…

Anyways, the link posted by zoto contains the information you need.

#5

That link describes how it works in Swing, but I’m not using Swing, I’m using TWL.

The ButtonCallback is refered to in the main widget’s constructor. Like so:

        btnConnect = new Button("Connect");
        btnConnect.addCallback(new ButtonCallback(this.game));
        add(btnConnect);

I assume TWL runs the runnable ‘ButtonCallback’ as a new thread when the button is clicked. (And indeed my run() code gets executed when I click the button).

Is this a problem of me not understanding threads, or is it specific to TWL and should I ask this question on a TWL forum?

Thanks

#6

Yeah it’s a problem about you not understanding threads :slight_smile: The callback will be performed in the same thread as the event is fired. So your callback actually needs to spawn a new Thread to do the actual asychronous work.

Cas :slight_smile:

#7

Thanks, I guess I assumed wrong :slight_smile:
I did what you said and it works now.

#8

Don’t forget to disable the button before the thread starts, and then enable it again when the thread finishes.

Cas :slight_smile: