Chapter 8 Frameworks

Frameworks

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

Example of FrameworksApplets (1)

Applet: Java program that runs in a web browser

Programmer forms subclass of Applet or JApplet overwrites

• Init• start• stop• destroy• paint

Example of FrameworksApplets (2)

init Called exactly once, when a class that extends

the Applet class. Purpose: Initialize data structures and add user

interface elementsstart

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.

Example of FrameworksApplets (3)

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.

Example of FrameworksApplets (4)

paint Called when the applet window needs

repainting. Purpose: Redraw the window contents to

reflect the current state of the applet data structures.

Example of FrameworksApplets (5)

Example of FrameworksApplets (6)

Sample Source Code: Shows scrolling banner

HTML page contains applet tag and parameters

<applet code="BannerApplet.class" width="300" height="100"> <param name="message" value="Hello, World!"/> <param name="fontname" value="Serif"/> <param name="fontsize" value="64"/> <param name="delay" value="10"/> </applet>

Example of FrameworksApplets (7)

ch8/applet/BannerApplet.java ch8/applet/BannerApplet.html

init method reads parameters start/stop start and stop timer paint paints the applet surface

Example of FrameworksApplets (8)