Choice class that implements
a popup menu component. Choices are fixed in a particular location.
The PopupMenu class, on the other hand, is activated when the user
holds the right mouse button or otherwise indicates that they want to pop up a menu. Typically this is used for context sensitive menus.
java.awt.PopupMenu is a subclass of of java.awt.Menu. For the most part you use it just like you use a regular menu. Items are added to it with the add(MenuItem mi) method, and user selections are responded to by installing an ActionListener on the MenuItem. For example, to build a popup menu with a number of URLs you might do this:
PopupMenu pm = new PopupMenu();
MenuItem mi = new MenuItem("http://www.javasoft.com/");
mi.addActionListener(URLActionListener);
pm.add(mi);
mi = new MenuItem("http://home.netscape.com/");
mi.addActionListener(URLActionListener);
pm.add(mi);
mi = new MenuItem("http://metalab.unc.edu/javafaq");
mi.addActionListener(URLActionListener);
pm.add(mi);
MenuItem mi = new MenuItem("http://www.roaster.com/news/");
mi.addActionListener(URLActionListener);
pm.add(mi);
PopupMenus don't belong to any particular MenuBar. Instead they're added to a component. For example, given a Frame f, you would install the PopupMenu pm in the frame by passing it to the frame's add() method, like so:
f.add(pm);
add() method used to add components to a frame?)
The exact trigger for popping up the menu is platform dependent.
For example, on Windows a PopupMenu is triggered on right mouse button up.
However, in Motif a PopupMenu is triggered on right mouse button down.
Regardless of the exact sequence of events leading to a menu popping up,
when the user makes a selection, when a MenuItem is selected an ActionEvent is fired to any listeners registered for that item.
A PopupMenu can be deinstalled from a component by passing it to the component's remove() method like this:
f.remove(pm);