Drop-down lists

WEBINAR: On-demand webcast

How to Boost Database Development Productivity on Linux, Docker, and Kubernetes with Microsoft SQL Server 2017 REGISTER >

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  • Your email address will not be published.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

  • As all sorts of data becomes available for storage, analysis and retrieval - so called 'Big Data' - there are potentially huge benefits, but equally huge challenges...
  • The agile organization needs knowledge to act on, quickly and effectively. Though many organizations are clamouring for "Big Data", not nearly as many know what to do with it...
  • Cloud-based integration solutions can be confusing. Adding to the confusion are the multiple ways IT departments can deliver such integration...

Most Popular Programming Stories

More for Developers

RSS Feeds

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