Save on Exit

Question

Hi,
I wanted to prompt for saving a file when the JFrame is getting closed. How can I implement this? Any suggessions would be helpful.
Thanks

Answer 1

First of all, you would need to stop the frame's defaultCloseOperation and substitute it with your own behavior. Here is a snippet from the main method of a program I have done this with:
   public static void main(String[ ] args)
      final MyAppFrame fr = new MyAppFrame();
      fr.setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);
      fr.addWindowListener(new WindowAdapter()
         { public void windowClosing(WindowEvent e)
            { fr.exitApp(); } });
   }When the Frame's close button is clicked, the exitApp() method is called. Here you can create a JOptionPane to ask the user if they want to save the file.
   public exitApp()
      JOptionPane option = new JOptionPane();
      int opt = option.NO_OPTION;
      if (fileHasChanged())   // ask if it should be saved
         Toolkit.getDefaultToolkit().beep();
         opt = option.showConfirmDialog(owner, "Save changes to current document?",
               "Exit", option.YES_NO_CANCEL_OPTION, option.WARNING_MESSAGE);
      if (opt == option.YES_OPTION) { saveFile();  System.exit(0); }   // save the file and exit
      else if (opt == option.NO_OPTION) { System.exit(0); }   // exit the application without saving
      else return;   // just go back to the program
}-Chris