1. INFSY 547: WEB-Based Technologies
Gayle J Yaverbaum, PhD
Professor of Information Systems
Penn State Harrisburg

2. Adding More Applets objects to XML Content
<?xml version="1.0"?>
<!DOCTYPE panelslayoutapplet SYSTEM "PanelLayoutsApplet.dtd">
<jclass>
<app class="panellayoutsapplet.PanelLayoutsApplet“
width="300" height="250">
</app>
<app class="firstapplet.FirstApplet" width="300" height="250">
<app class="urlapplet.URLApplet" width="300" height="250">
</jclass>

3. xsl Code <TR> <xsl:for-each select="app">
<TD width=“30%">
<applet>
<xsl:attribute name="code">
<xsl:value-of
</xsl:attribute>
<xsl:attribute name="width">
<xsl:value-of
<xsl:attribute name="height">
<xsl:value-of
</applet>
</TD>
</xsl:for-each>
</TR>

4. Run Saxon Processor

5. Applet Considerations
Javax.swing supplies best classes
setSize is unnecessary but aids in
debugging
applet size is set in html

6. package guisampleapplet;
import javax.swing.JApplet;
import java.awt.*;
public class GUISampleApplet extends JApplet {
PanelClass p;
public void init ()
p = new PanelClass(); }

7. Graphical User Example
package guisampleapplet;
import javax.swing.JApplet;
import java.awt.*;
public class GUISampleApplet extends JApplet {
PanelClass p;
public void init()
p = new PanelClass();
this.setSize(300, 40);
this.add("North", p); }
Extending our code!
BorderLayout

8. package guisampleapplet; import java.awt.Color;
import java.awt.FlowLayout;
import javax.swing.JButton;
import javax.swing.JPanel;
public class PanelClass extends JPanel {
JButton _button1, _button2, _button3;
JPanel _p;
public PanelClass() {
super();
_p = this;
designPanel(); }
private void designPanel() {
_p.setBackground(Color.blue);
_p.setLayout(new FlowLayout());
_button1 = new CreateAButton(_p, _button1, "Button 1 ",Color.orange);
_button2 = new CreateAButton(_p, _button2, "Button 2 ", Color.GREEN);
_button3 = new CreateAButton(_p, _button3, "Button 3 ", Color.YELLOW);

9. package guisampleapplet;
import java.awt.Color;
import javax.swing.JButton;
import javax.swing.JPanel;
public class CreateAButton extends JButton {
public CreateAButton (JPanel p, JButton b, String str, Color c)
super (str);
this.setBackground(c);
p.add (this); }

10. Layout Managers In JAVA Indicate layout of choice or accept default
layout is set in setLayout method
Indicate layout of choice or accept default
Add () and remove () methods are common to all layouts.

11. Popular Layout Managers
FlowLayout
GridLayout
BorderLayout

12. Panels A layout manager may apply to a panel or an applet as a whole
An applet may be divided into panels which may themselves be divided into subpanels and so on.

13. Panels Labels, buttons and more may be added to containers (panels)
Subsequently, panels are added to the applet

14. Complete all files to run your applet in
a browser
xml
dtd
xsl
css
bat
Run the applet in the browser

15. Add a class to create a label
Add labels between each button
Remove button labels
Change all button colors
Line up each button and label –
one/line using GridLayout
(see next slide and page 285 of text)

16. GridLayout package gridlayoutexample; import javax.swing.JApplet;
import javax.swing.JPanel;
import java.awt.*;
public class GridLayoutClass extends JApplet {
CreateAButton b;
JPanel j;
public void init ()
this.setBackground (Color.white);
j = new JPanel ();
j.setLayout(new GridLayout(5, 2));
for (int i=1; i<=10; i++)
b= new CreateAButton (j, i, Color.red, Color.white);
j.add (b); }
this.add(j);

17. package gridlayoutexample;
import java.awt.Color;
import javax.swing.JButton;
import javax.swing.JPanel;
public class CreateAButton extends JButton {
public CreateAButton (JPanel p, int x, Color c, Color f)
super ("Button " + x);
this.setBackground(c);
this.setForeground (f); }

18. Event Driven Programming
Code that is called by the system when an
event occurs
An event signifies an occurrence
The event generator notifies event handlers

19. Typical event handling
Text field
Object
Event Handling
Button Object
JAVA AWT Environment: Messages are sent between JAVA Objects
Screen
OS Interrupt
Event Notification
Update Text Field
Press Button
(Buttons generate events)
Typical event handling

20. Event Handling and Associated Objects
Interface Events Flow
User clicks a button
User types text
User uses a mouse
When an event occurs, applet is notified
Program may take action

21. Add implements action listener to the class public class PanelClass extends JPanel implements ActionListener Add to the action code to: _button1.addActionListener(this); for designPanel method 2. Do this for all of your buttons

22. public void actionPerformed(ActionEvent e) {
if (e.getSource() == _button1)
_button1.setBackground (Color.red);
_button2.setBackground (Color.blue);
_button2.setBackground (Color.yellow); }
Change all of the colors for each button clicked to a different color pattern

23. BorderLayout Manager o Divides the container (either a panel or whole
applet)
o Five areas
- North
-South
-East
-West
-Center
May also use the horizontal and vertical gaps as
in FlowLayout

24. BorderLayout Manager
North
West
South
East
Center

25. public void PlacePanels () { setLayout(new BorderLayout(5,10)); . }
Note: 1. may simply be (new BorderLayout ()
2. the 5,10 indicates border space in pixels

26. Pressing a mouse button triggers a mouse event
Rather than implementing ActionListener, you will
implement MouseListener (note that more than one listener
may be implemented)
When a mouse is pressed, the location is stored in x,y
coordinates and location may be retrieved with getx ()
and gety ().
MouseEvent handlers are invoked

27. Example on next slides demonstrate:
Mouse enter
Mouse exit
Left mouse click
Right mouse click

28. import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
public class mousedemo extends Applet implements MouseListener
{ //note that this bracket will having matching end bracket next screen
TextField mousetext;
public void init(){
mousetext = new TextField(25);
add(mousetext);
addMouseListener(this); }
public void mousePressed(MouseEvent e){
if((e.getModifiers()& InputEvent.BUTTON1_MASK)
== InputEvent.BUTTON1_MASK){
mousetext.setText("Left mouse button down at "
+ e.getX() + "," + e.getY()); }
else{
mousetext.setText("Right mouse button down at "

29. public void mouseClicked(MouseEvent e){
mousetext.setText("You clicked the mouse at " +
e.getX() + "," + e.getY()); }
public void mouseReleased(MouseEvent e){
mousetext.setText("The mouse button is up");
public void mouseEntered(MouseEvent e){
mousetext.setText("The mouse is in the applet");
public void mouseExited(MouseEvent e){
mousetext.setText("The mouse is out of the applet");
} //note that this bracket ends the applet from previous page