• 0

Java: Prevent opening duplicate dialogs


Question

I'm working on a java project that it has a menu where you can click File > Login to pop out a dialog for user to enter their login info.

My problem is, when the login dialog is present, user and focus back to the main JFrame and select File > Login to pop out another dialog. I'm searching for a way to prevent this from happening. So far I thought about two solutions but I don't know which is the best way to go about solving this kind of issue:

Solution 1: In my customzied JFrame class, declare a boolean that holds the visibility of the login dialog. Whenever the user goes File > Login, it will first check to see if it's already visible or not, then open the dialog if it's not already opened.

Solution 2: Prevent user to set focus back to the main JFrame when the dialog box is opened.

If you were me, how would you approach this problem? And which one is more effective or a common practice?

8 answers to this question

Recommended Posts

  • 0

erm... make the dialog modal. that should fix it.

if you don't want a modal dialog, you can have a private static bool isOpened=false;

that when it's opened it sets that to true and sets back to false when its closed. and on the creator of that dialog it just fails if the isOpened is true :p

i'd _really_ recommend the modal approach :p

  • 0
  Menge said:

erm... make the dialog modal. that should fix it.

if you don't want a modal dialog, you can have a private static bool isOpened=false;

that when it's opened it sets that to true and sets back to false when its closed. and on the creator of that dialog it just fails if the isOpened is true :p

i'd _really_ recommend the modal approach :p

That's not necessary. Create just one instance of it (global in your class that you're showing it in) and just have it so it hides when it closes:

myDialog.setDefaultCloseOperation(WindowConstants.HIDE_ON_CLOSE);

which is the default action.

And to make it visible:

myDialog.setVisible(true);

And if you're having to do some custom listener stuff for buttons and stuff and want to hide it after the user clicks it, put:

myDialog.setVisible(false);

in your action listener.

Edited by kjordan2001
  • 0
  kjordan2001 said:

That's not necessary. Create just one instance of it (global in your class that you're showing it in) and just have it so it hides when it closes:

myDialog.setDefaultCloseOperation(WindowConstants.HIDE_ON_CLOSE);

which is the default action.

And to make it visible:

myDialog.setVisible(true);

And if you're having to do some custom listener stuff for buttons and stuff and want to hide it after the user clicks it, put:

myDialog.setVisible(false);

in your action listener.

But if you do that, if people type info in the fields. You'll have to manually reset the fields, otherwise the next time the dialog shows, the info from the previous time the dialog was shown, will still be present.

  • 0
  Winston said:

But if you do that, if people type info in the fields. You'll have to manually reset the fields, otherwise the next time the dialog shows, the info from the previous time the dialog was shown, will still be present.

Just have it reset them in the submit action listener. Either way you'll have to do some work, question is which kind. Resetting or setting a variable.

  • 0

The best solution is to make the dialog a singleton ... ie only one instance can ever be created. Its called the singleton pattern. Its design pattern, google it

heres a quick example

public class MyFrame extends JFrame {

   public static MyFrame instance;

   private MyFrame() {
	 super(); 
   }

   public static MyFrame getInstance() {
	  if (instance = null)
		  instance = new MyFrame();
	  return instance;
   }

   main() {

	 MyFrame.getInstance().setVisbile(true);
	 ... or
	 MyFrame frame = MyFrame.getInstance();
	 frame.setVisible(true);
   }

   public void cleanup() {
	 instance = null;
  }
}

you will only ever get this one dialog only one instance can every be created. Note: you will need to free the instance yourself as the JVM will not clean it up.

This topic is now closed to further replies.
  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Posts

    • Seem like they are seeking for a one size fits all. You have power users and "what's a computer" generation growing up on phones, tablets, and Chromebooks.
    • Guessing it was profitable enough inserting prompted apps vs the hate it generated.
    • Also good for Debugging or troubleshooting your game.. i dont get it why nvidia app or amd does not show this data.. if steam can do it..
    • Microsoft reportedly planning to lay off thousands of employees, mostly in sales by Usama Jawad Back in May 2025, Microsoft decided to lay off 3% of its workforce, which amounted to roughly 6,000 employees. It claimed that this decision allowed it to implement better organizational changes in a "dynamic marketplace". Now, a new report claims that the Redmond tech firm is planning to lay off thousands more next month. Citing unnamed sources, Bloomberg reports that as the company continues investing heavily in its AI ventures, it is about to announce layoffs of thousands of workers as early as next month. This reduction in workforce will primarily affect sales teams, but they won't be the only ones affected. That said, the sources did mention that the timing for this announcement may change. This move, if true, won't be entirely surprising. In April 2025, Microsoft announced that it will be relying more on third-party firms to sell its software to small- and medium-sized customers. It's currently unclear how many employees will be impacted by this change, but even if the layoff percentage is in the single digits, it would still be significant as it would be impacting the professional careers of thousands. The May 2025 layoffs primarily impacted engineering and product teams. The other major round of layoffs prior to this was the decision to eliminate 10,000 jobs back in January 2023. Those represented 5% of the total workforce at that time, with numerous teams, including the one leading Mixed Reality (MR) efforts, being heavily impacted. It is interesting to note that if the timing of the announcement for layoffs is accurate, it would be soon after Microsoft closes its fiscal year at the end of June 2025. Although we'll get financial reports for the latest quarter soon after too, one has to wonder what the human cost of profit is, as Microsoft continues to report billions of dollars in revenue every quarter. Source: Bloomberg (paywall)
  • Recent Achievements

    • First Post
      Fuzz_c earned a badge
      First Post
    • First Post
      TIGOSS earned a badge
      First Post
    • Week One Done
      slackerzz earned a badge
      Week One Done
    • Week One Done
      vivetool earned a badge
      Week One Done
    • Reacting Well
      pnajbar earned a badge
      Reacting Well
  • Popular Contributors

    1. 1
      +primortal
      702
    2. 2
      ATLien_0
      285
    3. 3
      Michael Scrip
      212
    4. 4
      +FloatingFatMan
      194
    5. 5
      Steven P.
      131
  • Tell a friend

    Love Neowin? Tell a friend!