Follow Techotopia on Twitter

On-line Guides
All Guides
eBook Store
iOS / Android
Linux for Beginners
Office Productivity
Linux Installation
Linux Security
Linux Utilities
Linux Virtualization
Linux Kernel
System/Network Admin
Programming
Scripting Languages
Development Tools
Web Development
GUI Toolkits/Desktop
Databases
Mail Systems
openSolaris
Eclipse Documentation
Techotopia.com
Virtuatopia.com

How To Guides
Virtualization
General System Admin
Linux Security
Linux Filesystems
Web Servers
Graphics & Desktop
PC Hardware
Windows
Problem Solutions

  




 

 

Thinking in Java
Prev Contents / Index Next

Check boxes

A check box provides a way to make a single on/off choice. It consists of a tiny box and a label. The box typically holds a little “x” (or some other indication that it is set) or is empty, depending on whether that item was selected.

You’ll normally create a JCheckBox using a constructor that takes the label as an argument. You can get and set the state, and also get and set the label if you want to read or change it after the JCheckBox has been created.

Whenever a JCheckBox is set or cleared, an event occurs, which you can capture the same way you do a button: by using an ActionListener. The following example uses a JTextArea to enumerate all the check boxes that have been checked:

//: c14:CheckBoxes.java
// Using JCheckBoxes.
// <applet code=CheckBoxes width=200 height=200></applet>
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
import com.bruceeckel.swing.*;

public class CheckBoxes extends JApplet {
  private JTextArea t = new JTextArea(6, 15);
  private JCheckBox
    cb1 = new JCheckBox("Check Box 1"),
    cb2 = new JCheckBox("Check Box 2"),
    cb3 = new JCheckBox("Check Box 3");
  public void init() {
    cb1.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        trace("1", cb1);
      }
    });
    cb2.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        trace("2", cb2);
      }
    });
    cb3.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent e) {
        trace("3", cb3);
      }
    });
    Container cp = getContentPane();
    cp.setLayout(new FlowLayout());
    cp.add(new JScrollPane(t));
    cp.add(cb1);
    cp.add(cb2);
    cp.add(cb3);
  }
  private void trace(String b, JCheckBox cb) {
    if(cb.isSelected())
      t.append("Box " + b + " Set\n");
    else
      t.append("Box " + b + " Cleared\n");
  }
  public static void main(String[] args) {
    Console.run(new CheckBoxes(), 200, 200);
  }
} ///:~


The trace( ) method sends the name of the selected JCheckBox and its current state to the JTextArea using append( ), so you’ll see a cumulative list of the checkboxes that were selected and what their state is.
Thinking in Java
Prev Contents / Index Next


 
 
   Reproduced courtesy of Bruce Eckel, MindView, Inc. Design by Interspire