1. 11.1 Applets & graphics

2. What are applets?
Applets are programs that display and run in a web browser
Embedded in a web page
Include graphics, GUI and event handing capabilities
Must extend from the java.applet.Applet class

3. Launching applets
Applications are started by a call to the main method
Applets have no main method
Class file referenced in the HTML document
Browser loads and runs the Applet
JDK includes the appletviewer application

4. 11.1.3 Applets and security Applets could be invisible & malicious
Must be constrained to prevent attacks
Applet security rules
Cannot run another program
Cannot perform file I/O
Cannot call native methods
Cannot connect to any host other than the one that provided the Applet

5. 11.1.4 Embedding a Java applet
HTML tags are used to embed the Java applet
Use the APPLET tag to specify the class file and the window size

6. 11.2.1 Creating an applet Applets must extend java.applet.Applet
Require methods to handle events
Implement graphics and components, with appropriate layout managers

7. 11.4.1 Applet inherited methods
Applet inherits from Panel
Can be asigned a layout manager (the default is FlowLayout)
Other panels can be added
Listeners can register
Similar to other GUI applications

8. 11.4.2 Applet lifecycle methods
init(), start(), stop(), destroy()
init() is called when the applet is loaded
start() is called by init, and when the user returns to the page
stop() is called when the user leaves the page
destroy() is called when the browser is closed

9. 11.5.1 GUI components, color & fonts
Applets can implement a simple GUI
Use layout managers, color and fonts
Few restrictions other than the security controls
Applets need to be small

10. 11.5.4 Other applet methods Applet methods are called by the browser
Different browser events result in calls to the methods

11. 11.6.1 Applets and event-driven programming
Components can generate events in response to user interaction
Programmers create objects called handlers to react to these events
Handlers must register as a listener with the component that can generate the event

12. 11.7.1 Creating graphic objects
To draw in a component a Graphics object is required
Use the getGraphics() method to obtain an instance of Graphics
paint(), update() and repaint() are important members of the component class

13. 11.8 Case Study: JBANK Application