1. Slides prepared by Rose Williams, Binghamton University Chapter 18 Applets

2. © 2004 Pearson Addison-Wesley. All rights reserved18-2 Icons An icon is a picture –It is typically, but not always, a small picture An icon can be stored in a file of many different standard formats –Such as. gif,. tiff, or. jpg The class ImageIcon is used to convert a picture file to a Swing icon –Then it can be added as a component to any Container class, such as JApplet –The class ImageIcon is in the javax.swing package ImageIcon NameOfImageIcon = new ImageIcon("PictureFileName");

3. © 2004 Pearson Addison-Wesley. All rights reserved18-3 Adding Icons to an Applet The easiest way to display an icon in an applet is to place it in a JLabel The following three lines create a label, create an icon, and then add the icon to the label: JLabel aLabel=new JLabel("Welcome to my applet."); ImageIcon dukeIcon = new ImageIcon("duke_waving.gif"); aLabel.setIcon(dukeIcon); The character pictured in this icon is named Duke –He is Sun Microsystem's mascot for the Java language

4. © 2004 Pearson Addison-Wesley. All rights reserved18-4 An Applet with an Icon (Part 1 of 3)

5. © 2004 Pearson Addison-Wesley. All rights reserved18-5 An Applet with an Icon (Part 2 of 3)

6. © 2004 Pearson Addison-Wesley. All rights reserved18-6 An Applet with an Icon (Part 3 of 3)

7. © 2004 Pearson Addison-Wesley. All rights reserved18-7 Inserting an Applet in an HTML Document An applet can be placed in an HTML document with an applet tag: <applet code="PathToApplet" width=Number1 height=Number2> If given a.class file name only, then the HTML file and the applet file must be in the same directory –The PathToApplet can be a full or relative path name

8. © 2004 Pearson Addison-Wesley. All rights reserved18-8 Inserting an Applet in an HTML Document Note that the name of the.class file, not the.java file, is given Note also that the width and height of the applet is given in this command, and not within the applet class definition –The width and height are in pixels The following code, when placed in an HTML document, will display the calculator applet in a browser as shown <applet code="AppletCalculator.class" width=400 height=300>

9. © 2004 Pearson Addison-Wesley. All rights reserved18-9 An Applet in an HTML Document Vampire Control......

10. © 2004 Pearson Addison-Wesley. All rights reserved18-10 Browser View

11. © 2004 Pearson Addison-Wesley. All rights reserved18-11 Pitfall: Using an Old Web Browser An old browser may not be able to run applets from an HTML document –Even if a java application runs correctly on the same system Web browsers do not use the same Java Virtual Machine used to run regular Java applications –An old browser will have an old Java Virtual Machine, or perhaps, no Java Virtual Machine However, an applet viewer will work, as long as a recent version of Java is installed

12. © 2004 Pearson Addison-Wesley. All rights reserved18-12 Applets and Security An applet can be a program, written by someone else, that runs on your computer Whenever someone else's program runs on your computer, there are security questions you should ask: –Will it read information from your files? –Will it corrupt your operating system? Applets are designed so that they cannot do any of these things (at least easily)

13. © 2004 Pearson Addison-Wesley. All rights reserved18-13 Applet Examples http://www-math.mit.edu/daimp/

14. © 2004 Pearson Addison-Wesley. All rights reserved18-14 Handling Mouse Events The following example illustrates how mouse events can be responded to. –It also shows how a single listener can register with many sources. The event listener in this case will implement the MouseListener interface. MouseListener consists of five methods: void mouseClicked (MouseEvent me); // the mouse has been clicked on a component. void mouseEntered (MouseEvent me); // the mouse enters a component void mouseExited (MouseEvent me); // the mouse exits a component void mousePressed (MouseEvent me); // a mouse button has been pressed on a component void mouseReleased (MouseEvent me); // a mouse button has been released on a component Note: You are highly encouraged to check out details on implementing the KeyListener interface that defines keyboard events. The WindowListener interface shall be discussed in the next Chapter. Not in the BOOK 

15. Example 1.import javax.swing.*; 2.import java.awt.*; 3.import java.awt.event.*; 4.public class MouseEventTest extends JFrame { 5. JButton button = new JButton("Press Me"); 6. JLabel label = new JLabel( "Running Total:"); 7. JTextField textField = new JTextField(10); 8. public MouseEventTest() { 9. super("A Container With Components"); 10. setSize(300,100); 11. setLayout(new FlowLayout()); 12. add(label); add(textField); add (button); 13. setVisible(true); 14. class LightUpListener extends MouseAdapter { 15. public void mouseEntered(MouseEvent e) { 16. Component c = (Component)e.getSource(); 17. c.setBackground(Color.green); 18. } 19. public void mouseExited(MouseEvent e) { 20. Component c = (Component)e.getSource(); 21. c.setBackground(Color.red); 22. } 23. } 24. MouseListener listener = new LightUpListener(); 25. button.addMouseListener(listener); 26. textField.addMouseListener(listener); 27. getContentPane().addMouseListener(listener); } 1. public static void main(String[] args) { 2. new MouseEventTest(); 3. } 4.} Not in the BOOK 