1. ITEC324 Principle of CS III
Chapter 8 (Horstmann’s Book)
Frameworks
Hwajung Lee
ITEC324 Principle of CS III

2. 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

3. Example of Frameworks Applets (1)
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.

4. Example of Frameworks Applets (2)
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.

5. Example of Frameworks Applets (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.

6. Example of Frameworks Applets (4)
paint
Called when the applet window needs repainting.
Purpose: Redraw the window contents to reflect the current state of the applet data structures.

7. Example of Frameworks Applets (5)

8. Example of Frameworks Applets (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>

9. Example of Frameworks Applets (7)
ch8/applet/BannerApplet.java
ch8/applet/BannerApplet.html
init method reads parameters
start/stop start and stop timer
paint paints the applet surface

10. Example of Frameworks Applets (8)