Chapter 8 (Horstmann’s Book) Frameworks Hwajung Lee

 Framework is a set of cooperating classes and interface types that structures the essential mechanisms of a particular domain.  Example: Swing is a GUI framework  Framework != design pattern  Typical framework uses multiple design patterns  Inversion of control: framework controls execution flow

 Applet: Java program that runs in a web browser  Programmer  forms subclass of Applet or JApplet  overwrites ▪ Init ▪ start ▪ stop ▪ destroy ▪ paint

 init  Called exactly once, when a class that extends the Applet class.  Purpose: Initialize data structures and add user interface elements  start  Called when the applet is first loaded and every time the user restore the browser window containing the applet.  Purpose: Start or restart thread that perform animation or other tasks.

 stop  Called when the user hides the browser window containing the applet and when the browser terminates.  Purpose: Stop thread from updating the applet so computing resources are conserved when the applet is not being viewed.  destroy  Called when the browser terminates.  Purpose: Relinquish any resources that were acquired during init or other processing.

 paint  Called when the applet window needs repainting.  Purpose: Redraw the window contents to reflect the current state of the applet data structures.

 Sample Source Code: Shows scrolling banner  HTML page contains applet tag and parameters

 ch8/applet/BannerApplet.java ch8/applet/BannerApplet.java  ch8/applet/BannerApplet.html ch8/applet/BannerApplet.html  init method reads parameters  start/stop start and stop timer  paint paints the applet surface