Sychronize swing app with main

[venkata madugundu]

Hi, I am rather new to Swing. I have a java application which needs to pop up a dialog to capture certain user inputs. Till the dialog is closed, my caller method (say 'main') should block.

    

public static void main(String[] args) throws Exception 
	{	
		System.out.println("start");
		
		SwingUtilities.invokeAndWait(new Runnable() { /* i understand invokeAndWait waits only on Event Dispatch Thread. Is there any other way */
		    public void run() {
		        createAndShowDialog(); 
		    }
		});
			
		System.out.println("this should get printed after the above GUI is closed. But right now this is reached as soon as dialog is opened.");
	}

I tried to achieve that with SwingUtilities::invokeAndWait, but as I understand it only waits on Event Dispatch Thread. My main method is run in non EDT. So it obviously does not wait.
So is there any other simple and decent way without getting into the business of threading.

Thanks
Venkata Madugundu

[pete stein]

Just make the dialog (JDialog) modal, and that should take care of the blocking for you.

[venkata madugundu]

pete stein wrote:Just make the dialog (JDialog) modal, and that should take care of the blocking for you.

Wow. That worked. I tried JDialog before but didn't care to set its modal property to true. I was under the impression that JDialog itself is always modal. Thanks a ton. The code that worked...

    
public class ModalDialog
{
	public static void main(String[] args) throws Exception 
	{	
		System.out.println("start");
		
		SwingUtilities.invokeAndWait(new Runnable() {
		    public void run() {
		        createAndShowGUI();
		    }
		});
			
		System.out.println("this gets printed after above dialog is closed");
	}
	
    private static void createAndShowGUI()
    {
        /* the top level window or shell */
        JDialog dialog = new JDialog();
        dialog.setModal(true);
        dialog.setTitle("Lazy Tree");
        dialog.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        /* contents panel to hold controls */
        JPanel panel = new JPanel(new GridLayout(2, 2));
        createContents(panel);
        dialog.add(panel);

        /* show the top level window */
        dialog.pack();
        dialog.setVisible(true);
    }
    
    private static void createContents(JPanel parent)
    {
    	/* user */
    	JLabel lblUser = new JLabel("User:");
    	parent.add(lblUser);
    	
    	JTextField txtUser = new JTextField("Enter user name");
    	parent.add(txtUser);
    	
    	/* password */
    	JLabel lblPassword = new JLabel("Password:");
    	parent.add(lblPassword);
    	
    	JTextField txtPassword = new JTextField("*****");
    	parent.add(txtPassword);
    }
}

[pete stein]

My guess is that you'll want to pass a reference to a parent JFrame or other something similar via a parameter in your createAndShowGUI method. This way you can create the JDialog so that it is modal to this GUI component (check out the JDialog constructors for more on this). Best of luck and HTH.

[venkata madugundu]

pete stein wrote:My guess is that you'll want to pass a reference to a parent JFrame or other something similar via a parameter in your createAndShowGUI method. This way you can create the JDialog so that it is modal to this GUI component (check out the JDialog constructors for more on this). Best of luck and HTH.

Even without a parent JFrame, the JDialog came up standalone and only when the dialog was closed, the control returned to the caller method, 'main'. This is what I needed. The code that I posted worked. Thanks again for your helpful hint.

[Michael Dunn]

you still should supply a parent to the dialog.

as you stated it works OK, but run it again, then change focus to another program.
the dialog vanishes, and you have to alt-tab or minimize everything to find it.

if the dialog has a parent, you only need to click the parent's item in the taskbar for the dialog to reappear/regain focus

[Maneesh Godbole]

JOptionPane has several showXXX dialogs. Using them is much easier than creating your own dialogs.

[venkata madugundu]

Michael Dunn wrote:you still should supply a parent to the dialog.

as you stated it works OK, but run it again, then change focus to another program.
the dialog vanishes, and you have to alt-tab or minimize everything to find it.

if the dialog has a parent, you only need to click the parent's item in the taskbar for the dialog to reappear/regain focus

I understand what you are saying. Infact that ALT+TAB thing is annoying and at times it is hard to figure out that the dialog has gone back and is hiding :-). I will try and see if I can parent the JDialog with a frame. Thanks Michael.

[venkata madugundu]

Maneesh Godbole wrote:JOptionPane has several showXXX dialogs. Using them is much easier than creating your own dialogs.

I actually needed a tree control and some set of buttons on the dialog. So I was not too sure if JOptionPane could serve the purpose. But anyways, thanks for your inputs Maneesh, and I will see if JOptionPane can fit in my requirements.

[Maneesh Godbole]

The showXXXDialog takes an object as the message argument.
You can construct your tree and other required controls, put it on a panel, and pass the panel as the argument. Since panel is an Object, the dialog will happily display it correctly for you!