Chapter 14: Widget Wizardry

Quiz

1. What is the purpose of an action method?

   The action method lets you handle the activation of a component, i.e. a user action directod at a widget.

2. When is the action method called?

   Any time an event occurs in a Component.

Exercises

1. Modify the fortune teller applet so that it reads the fortunes out of an indefinite number of PARAM tags and randomly selects the fortune.

   
   import java.applet.Applet;    
   import java.awt.Label;
   import java.awt.Button;
   import java.awt.Event;
   import java.util.Vector;
   
   
   public class Fortune extends Applet {
   
     Vector fortunes;
     Label l;
   
     public void init() {
       l = new Label("Your Fortune for a nickel");
       add(l);
       add (new Button("A Nickel"));
       
       int i = 1;
       String nextline;
       fortunes = new Vector();
   
       while ((nextline = getParameter("fortune" + i++)) != null) {
          fortunes.addElement(nextline);
       }
   
     }
     
     public boolean action(Event e, Object o) {
     
       if (e.target instanceof Button) changeFortune();
       return true;
       
     }
   
     public void changeFortune() {
     
       int i = (int) (Math.random() * fortunes.size());
     
       l.setText((String) fortunes.elementAt(i));
       
     }
   
   }