Drop-Down Menus

Drop-down menus help to organize and reduce the clutter of command options.  GUI-based programs add labeled menus to a menu bar, and then add labeled command options to a menu.  In a BreezySwing application, the programmer adds a command option, also called a menu item, to a menu in one operation, which has the form

menuItem = addMenuItem(menuName, menuItemName)

This method expects two strings as arguments and returns an inance of the Java class JMenuItem. The next code segment adds a simple File menu, with the options New, Open, and Save, and an Edit menu, with the options Copy, Cut, and Paste, to the window's menu bar.

 

JMenuItem newMI   = addMenuItem("File", "New");

JMenuItem openMI  = addMenuItem("File", "Open");

JMenuItem saveMI  = addMenuItem("File", "Save");

JMenuItem copyMI  = addMenuItem("Edit", "Copy");

JMenuItem cutMI   = addMenuItem("Edit", "Cut");

JMenuItem pasteMI = addMenuItem("Edit", "Paste");

 

 

The menus are added to the menu bar, from left to right, in the order in which their names appear in your code. Likewise for the menu items, from top to bottom within each menu.  

BreezySwing includes a method named menuItemSelected to respond to the user's menu item selections.   When the user selects a name in a drop-down menu, this event handler method is triggered. As with button clicks, the user overrides this method to determine which option was selected and to provide the appropriate response.

To demonstrate the use of menus, the next example program displays a label and a set of menus to set the label's font and color properties. A font has three basics properties: a name, a style, and a size. A label has a font and a foreground color as properties. The program's menus are named Name, Size, and Color (we ignore the style for now). When the user selects a menu option, the program updates the label with the changes. Here is a screen shot of the window, followed by the code for the program:

public class MenuDemo extends GBFrame{

 

    // Add the window components

    JLabel textLabel      = addLabel    ("Text font", 1,1,1,1);

    JMenuItem itemCourier = addMenuItem ("Name", "Courier");

    JMenuItem itemVerdana = addMenuItem ("Name", "Verdana");

    JMenuItem item14      = addMenuItem ("Size", "14");

    JMenuItem item24      = addMenuItem ("Size", "24");

    JMenuItem itemRed     = addMenuItem ("Color", "Red");

    JMenuItem itemBlue    = addMenuItem ("Color", "Blue");

 

   // The event handler method for menu items    

   public void menuItemSelected(JMenuItem menuItem){

       Font font = textLabel.getFont();

       String name = font.getFontName();

       int style = font.getStyle();

       int size = font.getSize();

       Color color = textLabel.getForeground();

       if (menuItem == itemVerdana)

           textLabel.setFont (new Font ("Verdana", style, size));

       else if (menuItem == itemCourier)

           textLabel.setFont (new Font ("Courier", style, size));

       else if (menuItem == item14)

           textLabel.setFont (new Font (name, style, 14));

       else if (menuItem == item24)

           textLabel.setFont (new Font (name, style, 24));

       else if (menuItem == itemRed)

           textLabel.setForeground (Color.red);

       else if (menuItem == itemBlue)

           textLabel.setForeground (Color.blue);

    }

 

   // Create and display the window when the app launches

   public static void main(String[] args){

      JFrame frm = new MenuDemo();

      frm.setTitle("Text Fonts");

      frm.setSize (200, 100);

      frm.setVisible (true);

   }

}