COP 4331 – OOD&P Lecture 6

Review Midterm Review Complete sample application –See SwingColorTest.java

TYJ Day 13 – Graphics Graphic operations are preformed on a canvas such as a JPanel Suppose JFrame main is the main panel Gain access to the current display area with code like Container content = main.getConentPane(); – add() method can be applied to content –Can also draw on it

TYJ Day 13 – Graphics.2 Every canvas has a – paintComponent(Graphics g) method –This method is called whenever the image must be displayed or updated –Can be overridden to draw graphic objects –Cast g to (Graphics2D) g to apply drawing methods

Graphics2D Coordinates Coordinate system –Upper left corner is 0,0 –Unit is pixel

Drawing Text Given that comp2D is a Graphics2D object Use the drawString(str, x, y) –Where str is the string to display – x, y are the coordinates to start the string

Fonts Font class constructor Font (“font name”, Font.STYLEs, pts) Get information about a font with FontMetrics fm = getFontMetrics(f); –Accessors can get characteristics getSize(), stringWidth(s), etc.

Colors Color class objects provide color information new Color(r, g, b) –color values range from 0 to 255 –Some color names are predefined, e.g. Color.white, Color.red, etc. – setBackground(c), setForeground(c) –Can also get colors.

TYJ Day 14 – Applets Applet class defines applets Applet runs in a web page under browser Applet security –Cannot read or write files on user system –Cannot communicate with internet site other than one that loaded them –Cannot run programs on browser’s system –Cannot load programs from user’s system

Applet Structure Instead of main() applet has methods that are invoked under particular situations – init() runs once when applet is loaded –start() runs each time applet starts – stop() runs when user leaves page – destroy() runs when applet is destroyed – paint(Graphics screen) runs whenever the screen must be redrawn Default methods are empty

Example Applet See Watch.java

The Tag The applet tag specifies the location and characteristics of an applet on a web page alternate text

The Tag.2 Other fields –HSPACE, VSPACE specify padding around applet –CODEBASE indicates location of applet code if not the same as the web page Applet can be viewed outside a web page with appletviewer

Applets.3 The OBJECT tag is a more general alternative to the APPLET tag See Watch2.html Java archives permit packaging all files needed for an applet into a single file

Applet Parameters Can pass parameters to applet with tags –Retrieved in applet with getParameter(“name”); See NewWatch.java and NewWatch.html