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.

Answer 1

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