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GRAPHICS APPLICATIONS
The introduction to Java’s graphics context, found in the previous
topic Graphics Context, uses a Java applet to illustrate the concept. It is
also possible to do graphics in a Java application. To create a visible
window for a Java application you build an object of class
javax.swing.JFrame. This class is also a subclass of
java.awt.Container and, therefore, inherits the paint method.
To create an application with a GUI window, make the application a
subclass of javax.swing.JFrame. The application object will
have paint as an instance method, which you can morph similarly to
an applet. For a more complete discussion of the JFrame class and its
use to create a GUI window, see the topic GUI Applications.
java.awt.Component
IS_A
java.awt.Container
IS_A
java.awt.Window
IS_A
java.awt.Frame
Example
The application shown below creates this GUI window. The
morphed paint method is identical to that in the applet
GraphicsAppletDemo of the previous section Graphics Context.
Graphics Applications
IS_A
javax.swing.JFrame
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import javax.swing.JFrame;
import java.awt.*; // Graphics, Color, Font
public class GraphicsAppDemo extends JFrame
{
public static void main( String [] args )
{ // call app constructor
new GraphicsAppDemo( "My Window" );
}
public GraphicsAppDemo( String title ) // app constructor
{
super( title ); // call JFrame constructor
this.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
this.setSize( 500, 250 );
this.setVisible( true );
}
public void paint( Graphics g )
{
super.paint( g );
g.setColor( Color.RED );
g.setFont( new Font( "Trebuchet MS", Font.PLAIN, 24 ) );
g.drawString( "Welcome to Graphics", 20, 100 );
}
}
Exercises
1.
Modify GraphicsAppletDemo so that it uses a
JOptionPane input dialog to read the user’s name
and displays a message with the name, such as shown to
the right.
Graphics Applications
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