Drop-down lists

Bruce Eckel's Thinking in Java Contents | Prev | Next

//: Choice1.java
// Using drop-down lists
import java.awt.*;
import java.applet.*;
 
public class Choice1 extends Applet {
  String[] description = { "Ebullient", "Obtuse",
    "Recalcitrant", "Brilliant", "Somnescent",
    "Timorous", "Florid", "Putrescent" };
  TextField t = new TextField(30);
  Choice c = new Choice();
  Button b = new Button("Add items");
  int count = 0;
  public void init() {
    t.setEditable(false);
    for(int i = 0; i < 4; i++)
      c.addItem(description[count++]);
    add(t);
    add(c);
    add(b);
  }
  public boolean action (Event evt, Object arg) {
    if(evt.target.equals(c))
      t.setText("index: " +  c.getSelectedIndex()
        + "   " + (String)arg);
    else if(evt.target.equals(b)) {
      if(count < description.length)
        c.addItem(description[count++]);
    } 
    else 
      return super.action(evt, arg);
    return true;
  }
} ///:~ 

The TextField displays the “selected index,” which is the sequence number of the currently selected element, as well as the String representation of the second argument of action( ), which is in this case the string that was selected.

When you run this applet, pay attention to the determination of the size of the Choice box: in Windows, the size is fixed from the first time you drop down the list. This means that if you drop down the list, then add more elements to the list, the elements will be there but the drop-down list won’t get any longer [57] (you can scroll through the elements). However, if you add all the elements before the first time the list is dropped down, then it will be sized correctly. Of course, the user will expect to see the whole list when it’s dropped down, so this behavior puts some significant limitations on adding elements to Choice boxes.


[57] This behavior is apparently a bug and will be fixed in a later version of Java.



Comments

  • There are no comments yet. Be the first to comment!

Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • U.S. companies are desperately trying to recruit and hire skilled software engineers and developers, but there is simply not enough quality talent to go around. Tiempo Development is a nearshore software development company. Our headquarters are in AZ, but we are a pioneer and leader in outsourcing to Mexico, based on our three software development centers there. We have a proven process and we are experts at providing our customers with powerful solutions. We transform ideas into reality.

  • Lenovo recommends Windows 8 Pro. "I dropped my laptop getting out of the taxi." This probably sounds familiar to most IT professionals. If your employees are traveling, you know their devices are in for a rough go. Whether it's a trip to the conference room or a convention out of town, any time equipment leaves a user's desk it is at risk of being put into harm's way. Stay connected at all times, whether at the office or on the go, with agile, durable, and flexible devices like the Lenovo® …

Most Popular Programming Stories

More for Developers

RSS Feeds

Thanks for your registration, follow us on our social networks to keep up-to-date