From JavaProgramming
'''Overview of graphical components in JavaAwt. Simple examples of an application with a GraphicalUserInterface and a JavaApplet'''
http://www.datapharm.dk/ht/java/awtcomp.gif
* Microsoft Windows API is based on Windows and graphical compo-nents on windows (buttons, text fields, etc.)
* Java AWT (Abstract Window Toolkit) is 100% Object-Oriented. Meaning that all graphical components inherits from the same base classes
* This goes for both GUI applications and Applets
* A container is an area, which contains a number of components, i.e. a panel with buttons
* A panel is a GUI area, which contains components or graphic drawing
* An Applet is a specialisation of a panel, which can be con-tained within a website
* A Frame is a window in a GUI application
* A Frame can contain all components that inherit from class Component (that includes Applets see example of an Applet that can run as a GUI application later in this document)
'''Write a GUI application'''
* Inherit from class Frame
* Add an event listener for closing the application when receiv-ing a close event
* Call Frame::setVisible() to make the window visible
/* H''''''elloWorldFrame.java */
import java.awt.*;
import java.awt.event.*;
public class H''''''elloWorldFrame extends Frame {
public static void main(String[] args) {
H''''''elloWorldFrame frame = new H''''''elloWorldFrame();
Panel panel = new Panel();
frame.add(panel);
// Add event listener to close the application
frame.addWindowListener(new W''''''indowAdapter() {
public void windowClosing(W''''''indowEvent e) {
System.exit(0);
}
});
frame.setTitle("HelloWorldFrame");
frame.setSize(400,320);
// Call setVisible() to make the frame visible
frame.setVisible(true);
panel.getGraphics().drawString("Hello world!", 20, 20);
}
}
'''Write an Applet'''
* Inherit from class Applet
* Overwrite the method Applet::paint() to update graphics
/* H''''''elloWorldApplet.java */
import java.awt.*;
import java.applet.*;
public class H''''''elloWorldApplet extends Applet {
public void paint(Graphics g) {
g.drawString("Hello world!", 20, 20);
}
}
'''Show an Applet on a website'''
* Compile the .java file to a .class file
* Add tag <applet> to the .html file
* Set the value code = the .class file
* Set the value codebase = the path to the .class file relative to placement of the .html file
* Set the values width and height to determine the size of the Applet
/* H''''''elloWorldApplet.html */
<html>
<head>
<title>
Test H''''''elloWorldApplet
</title>
</head>
<body>
<applet
code = "H''''''elloWorldApplet.class"
codebase = "."
width = "400"
height = "300"
>
</applet>
</body>
</html>
'''Write an Applet that can run as a GUI application'''
Graphical components may be included in both GUI applications and Applets. The program below demonstrates this.
/* S''''''tandAloneApplet.java */
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class S''''''tandAloneApplet extends Applet {
public void paint(Graphics g) {
g.drawString("Hello world!", 20, 20);
}
public static void main(String[] args) {
Frame frame = new Frame();
S''''''tandAloneApplet applet = new S''''''tandAloneApplet();
frame.add(applet);
// Add event listener to close the application
frame.addWindowListener(new W''''''indowAdapter() {
public void windowClosing(W''''''indowEvent e) {
System.exit(0);
}
});
frame.setTitle("Standalone Applet");
frame.setSize(400,320);
frame.setVisible(true);
}
}