Other Java Topics - Java for COBOL Programmers - page 287

E XERCISES

Even though you haven't explored in depth how to create a GUI, you are going to
walk through a simple example. To start, copy the file SimpleFrame.java from the
Chapter12 subdirectory in the Exercises directory on the CD-ROM to your
java4cobol directory.

ON THE DVD

1. Compile the SimpleFrame class. SimpleFrame takes care of the work of cre-
ating a frame window and various listeners so that the window will re-
spond properly to messages. It also provides some utility methods for
creating buttons and menu items. You won't be using a menu in this exer-
cise, but you will be creating a button.
2. Create a new Java file called MyFrame.java. Add the following import state-
ments to the file.

import javax.swing.*;
import javax.swing.event.*;
import java.awt.*;
import java.awt.event.*;

3. Write the code to create the MyFrame class. Notice that MyFrame must extend
SimpleFrame for this exercise to compile correctly.

public class MyFrame extends SimpleFrame
{
}

4. Add a constructor. This constructor invokes the constructor in Simple-
Frame. The text “My Frame” will become the title on the window.

public MyFrame()
{

super("My Frame");

}

5. Override the buildGUI() method in SimpleFrame . This method is automat-
ically invoked in the SimpleFrame constructor.

public void buildGUI()
{
// Call the createButton method in SimpleFrame.
JButton button = createButton("Click me", "Click me");