Button opens new JFrame multiple times. How do I stop this?

Question

I am using to different classes: one holding a main JFrame with a button, and one holding a new JFrame that is called upon at a button press.

if( event.getSource() == noteBtn ) { MiniPad.pad(); return;}

(MiniPad.pad() references the class and pad() method on the new JFrame)

When I removeAll() on the JPanel that hosts the button, and then revalidate() and repaint(), the button opens the JFrame multiple times, which isn't what I want it to do at all.

Is there a way to tell the MiniPad class that you can't have more than one copy of the JFrame open at any one time? I extend the JFrame by the way, in case that's any help.

how would you know the frame is closed? if you are waiting for it to close, you could use a boolean value to indicate whether the frame is open. — elyashiv, Aug 14 '12 at 11:21
This [example](http://stackoverflow.com/a/9443609/1057230) can give you some idea, though don't use two `JFrame`s, instead stick to one `JFrame multiple JDialog` thingy as very much adviced by @AndrewThompson :-) — nIcE cOw, Aug 14 '12 at 11:56

score 3 · Answer 1 · edited May 23 '17 at 10:24

3

The best solution is to open a modal dialog instead of the frame. See The Use of Multiple JFrames, Good/Bad Practice? for more.

edited May 23 '17 at 10:24

Community

1
1

answered Aug 14 '12 at 11:25

Andrew Thompson

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score 3 · Accepted Answer · edited May 23 '17 at 12:10

Edit: Everything below is valid programming knowledge, but you might also want to consider having MiniPad extend the JDialog class instead. I haven't used it before, but its implementation looks a lot like JFrame. You might not actually have to change much in your MiniPad class. The documentation is here: http://docs.oracle.com/javase/7/docs/api/javax/swing/JDialog.html

If you're wondering why, check out Andrew Thompson's post here.

--

From what I understood of your question, MiniPad extends JFrame, and the pad() method creates a new instance of the MiniPad class. The simplest solution would be to turn the MiniPad class (at least through the pad() method) into a singleton. A singleton is a type of class where only one instance (or object) can exist at any given time. By calling a static method (in this case pad()) you check to see if an instance of the object already exists; if it does, simply use that existing object:

public class MiniPad extends JFrame {

    //whatever code you have

    private static MiniPad padInstance = null; //the singleton instance of your MiniPad

    public static MiniPad pad() {
        if(padInstance == null)
            padInstance = new MiniPad();
        //If you want to reset the object every time you call the method for whatever reason, do it here
        pad.setVisible(true); // I believe this is all you want to do
    }
}

This should do what you want. By calling the pad() method, only one MiniPad will ever show up.

However, if I read your question wrong, let me know and I will revise my answer.

Info on singletons: http://en.wikipedia.org/wiki/Singleton_pattern

please did you read advice by one of top posters here, then again [The Use of Multiple JFrames, Good/Bad Practice?](http://stackoverflow.com/a/9554657/714968) — mKorbel, Aug 14 '12 at 11:45

Button opens new JFrame multiple times. How do I stop this?

2 Answers2