1. Creating Graphics in Java CSE301 University of Sunderland Harry R Erwin, PhD

2. Resources Flanagan, David (2000). Java Foundation Classes in a Nutshell, O’Reilly. Darwin, Ian F. (2004). Java Cookbook, O’Reilly. Flanagan, David (2004). Java Examples in a Nutshell, O’Reilly.

3. Java GUI Frameworks Abstract Window Toolkit (java.awt) –The original set of windowing components designed for Java. These were implemented as separate processes using the GUI features of the underlying operating system. Swing (or Java Foundation Classes—javax.swing) –A second generation set of ‘light-weight’ windowing components introduced in Java 1.2. These were implemented as Java threads and so avoided the overhead of process context switches and enforced a common look and feel. SWT (part of Eclipse) Discussed at: http://java.sun.com/docs/books/tutorial/uiswing/index.html http://java.sun.com/docs/books/tutorial/uiswing/index.html

4. Goals The goal of these two lectures is to provide the student an understanding of graphics in Java. GUI1 explores the Java 2D API, the basic graphics primitives. GUI2 explores image processing, image I/O, and animation.

5. Review of AWT The foundation of GUI in Java Implemented in separate processes Rudimentary Supported by most web browsers, so that most applets should use AWT instead of Swing.

6. AWT Graphics Features Basic facilities for creating a graphical user interface. Drawing graphics –java.awt.Graphics –java.awt.Color –java.awt.Font Java 2D API (added in Java 1.2) –java.awt.Graphics2D

7. Using AWT Import: –java.awt.* –java.awt.event.* Everything inherits from java.awt.Component, including graphics. The AWT GUI is organized by containers, inheriting from java.awt.Container (which inherits from Component). The arrangement of controls is managed by various layout managers. Notification of changes is handled by events and event listeners that run in a GUI thread.

8. Graphics Before Java 1.2 Demonstrated in GraphicsSampler.java from Java Examples in a Nutshell (library). init() is called to initialise color resources. paint() is called every time the object needs to be redrawn, for example when the applet is covered by another window and the window moves or disappears.

9. The Graphics Object Used for all graphics operations prior to 1.2 Represents a drawing surface. Can be used to draw on a Component, Image, or printer. Keeps track of the current state. Provides attributes and methods for drawing.

10. java.awt.Graphics An interface. Cannot be created directly. You must: –use getGraphics() on a Component –use getGraphics() on an image or PrintJob –copy from an existing Graphics object using create(). When no longer needed, call dispose() on it to free up the system resources it uses.

11. Graphics Attributes Color, the current Color object Font, the current Font object Clipping region, the Rectangle to be painted Origin, a point Paint mode, a boolean Background color, a Color

12. Graphics Operations drawLine() (1 pixel) drawPolyLine() (polygon) drawArc() drawOval() drawPolygon() drawRect() drawRoundRect() draw3DRect() fillArc() fillOval() fillPolygon() (polygon) fillRect() fillRoundRect() fill3DRect() drawBytes() (byte[]) drawChars() (char[])

13. More Graphics Operations drawString() drawImage() –various versions, requiring an ImageObserver object clearRect() various setters and getters copyArea() clipRect() translate() hitClip() translate()

14. java.awt.Font Represents a font. The constructor is passed a name, a style (PLAIN, BOLD, ITALIC, BOLD+ITALIC), and a font size. Names include: –“serif” –“sansserif” –“monospaced” –“Dialog” –“DialogInput” –“Symbol”

15. java.awt.Color Represents colors. Can represent a color coded in RGB space defined from integers or floating point numbers. Has a static method that allows you to create colors in the HSB color space. Provides some standard colors as constants, such as Color.black or Color.white. java.awt.SystemColor is a subclass with constants for various colors used on the system desktop.

16. java.awt.Rectangle Defines a rectangle using the x and y coordinates of the upper left corner and the width and height. These four values are public and can be manipulated directly. Used to define rectangular regions, usually in an image being manipulated. Can be used for other purposes.

17. java.awt.Point A concrete subclass of java.awt.geom.Point2D A Point is defined as two integers, x and y. These are public fields and can be manipulated directly. equals() is overridden so two points are equal if they have the same x and y values. hashCode() doesn’t appear to be overridden, so don’t use a Point as an index in a HashMap with the expectation that it will be a value class.

18. This Week’s Exercise Access http://www.oreilly.com/catalog/jenut3http://www.oreilly.com/catalog/jenut3 Download the sample code and create an Eclipse project for GraphicsSampler.java (an Applet) Run the Applet in the debugger so you can observe how it works.