Java Swing Tips

Opening and saving files using a JFileChooser

This example shows how to use a single filechooser to open and save. The filechooser will remember the directory it entered last which makes it a lot easier for the user. openFile and saveFile can be buttons or menu items with an ActionListener:

public void actionPerformed(ActionEvent event)
{
   Object source = event.getSource();

   if (source == openFile)
   {
      if (fileChooser.showOpenDialog(this) == JFileChooser.APPROVE_OPTION)
      {
         try
         {
            File file = fileChooser.getSelectedFile(); //get file(path+name)
            BufferedReader in = new BufferedReader (new FileReader(file));
            //in.readLine() etc
         }
         catch (Exception e) { //ignore...
         }
      }
      else { //user cancelled...
      }
   }
   else if (source == saveFile)
   {
      if (fileChooser.showSaveDialog(this) == JFileChooser.APPROVE_OPTION)
      {
         try
         {
            File file = fileChooser.getSelectedFile();
            PrintWriter out = new PrintWriter(file);
            //out.print() etc
            out.close();
         }
         catch (Exception e) { //ignore...
         }
      }
      else { //user cancelled...
      }
   }

Making JPopupMenu pop up

Create the JPopupMenu and add JMenuItems to it (and ActionListeners to the items) like a normal JMenu. But instead of adding it to a menubar, wrap it in a class that implements MouseAdapter, and use addMouseListener() to add the listener to the item to popup over:

rightClickMeComponent.addMouseListener(new PopupListener(popupMenu))

You create the PopupListener class - it needs to call popupMenu.show() to show the popup when the events are right. This sample PopupListener is a slightly modified version of the one from the Sun-era Java Tutorial (no longer online, thanks Oracle):

public class PopupListener extends MouseAdapter
{
   JPopupMenu popup;

   PopupListener(JPopupMenu popupMenu)
   {
         popup = popupMenu;
   }

   public void mousePressed(MouseEvent e)
   {
         if (e.isPopupTrigger())
             popup.show(e.getComponent(), e.getX(), e.getY());
   }

   public void mouseReleased(MouseEvent e)
   {
         if (e.isPopupTrigger())
             popup.show(e.getComponent(), e.getX(), e.getY());
   }