1 / 27

Creating a graphics program

Creating a graphics program Color and Shapes Import libraries import javax.swing.*; // for JFrame import java.awt.*; // for Color and Graphics Program Framework public class myGrPgm extends JFrame { // extending JFrame gives us: // - windows // - paint

jacob
Download Presentation

Creating a graphics program

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Creating a graphics program Color and Shapes

  2. Import libraries import javax.swing.*; // for JFrame import java.awt.*; // for Color and Graphics

  3. Program Framework public class myGrPgmextends JFrame { // extending JFrame gives us: // - windows // - paint // - use of Color }// end class myGrPgm

  4. grab a color public Color palette = new Color ( 25, 120, 200 ); // “palette” is a Color object // Color (red,green, blue); note: 25, 120, 200 is ocean blue

  5. how colors are defined

  6. a clarification Color boxColor = Color.blue or Color boxColor = new Color( ); boxColor = Color.blue;object t to box Color.

  7. Color class in Computer Memory Space Color boxColor = Color.blue uses library directly! JFrame library Color.blue Color.green Color.red Color.pink

  8. Color class in Computer Memory Space Color boxColor = new Color( ); boxColor = Color.blue; Color.blue a copy! Color.green Color.red Color.pink ready for Color Color.blue

  9. add “the usual” main public static void main(String args [ ]) { myGrPgm app = new myGrPgm( ); } // causes a constructor to be run

  10. so far… import javax.swing.*; // for JFrame import java.awt.*; // for Color and Graphics public class myGrPgm extends JFrame { public Color palette = new Color ( 25, 120, 200 ); // real work gets done here public static void main(String args [ ]) { myGrPgm app = new myGrPgm( ); } } // end class myGrPgm

  11. a constructor // sets up a “Frame” public myGrPgm( ) { setSize( 400, 400 ); setLocation( 20, 40 ); setDefaultCloseOperation( EXIT_ON_CLOSE ); setVisible( true ); } // uses JFrame methods, because WE are JFrame // i.e. “this” class we’re in is a JFrame child

  12. graphics on a computer X direction ( 0, 0 ) ( 1024, 0 ) ( ?, ? ) y direction ( 0, 768 ) ( 1024, 768 )

  13. a better constructor // sets up a “Frame” public myGrPgm( int width, int height) { setSize( width, height ); setLocation( 20, 40 ); setDefaultCloseOperation( EXIT_ON_CLOSE ); setVisible( true ); } // uses JFrame methods, because WE are JFrame // i.e. “this” class we’re in is a JFrame child

  14. change main public static void main(String args [ ]) { myGrPgm app = new myGrPgm( 400, 400 ); } supplied to constructor

  15. so far… import javax.swing.*; // for JFrame import java.awt.*; // for Color and Graphics public class myGrPgm extends JFrame { public Color palette = new Color ( 25, 120, 200 ); public myGrPgm( int width, int height) { setSize( width, height ); setLocation( 20, 40 ); setDefaultCloseOperation( EXIT_ON_CLOSE ); setVisible( true ); } public static void main(String args [ ]) { myGrPgm app = new myGrPgm( 400, 400 ); } } // end class myGrPgm

  16. last method • being a JFrame, means that we can USE JFrame methods like “setLocation( … ” • being a JFrame, means that we can re-write methods that are IN JFrame for more power, like “paint(… ”

  17. what is paint? • a method in JFrame • it’s a “void” method (returns nothing to the caller ); • called by the computer automatically • that we re-write (“override”) • that someone else wrote • that uses a Graphics helper class • that puts colors and shapes in a JFrame

  18. Graphics helper class? • look up the Graphics class on the Sun Java website • It must be used by a paint method in a JFrame class • it contains variables and methods of its own, to color and draw shapes

  19. structure of a paint method public void paint( Graphics g ) // g is the Graphics copy (object) { // set a color g. setColor( pallette ); // do something with the color // g.fillRect( x, y, width, height ); g.fillRect( 50, 100, 200, 200 ); }

  20. setting a color • use our public color “pallette” • or use a primary color g.setColor( Color.green );

  21. helps to set the background // make width and height public, and static public static int winHeight = 400 public static int winWidth = 400; // use in paint, or wherever you need window size: public void paint( Graphics g ) {// set background g.setColor( Color.white ); g.fillRect( 0, 0, winHeight, winWidth ); g.setColor( palette ); g.fillRect( 50, 100, 200, 200 ); }

  22. static? • whenever you decide something is unique, will never be anything with the same name anywhere in your program • main is static • any variable or method used by main must be static

  23. use winHeight and winWidth public static void main( String args [ ] ) { myGrPgm app = new myGrPgm( winHeight, winWidth ); }

  24. demo see the myGrPrm example

  25. Using Arrays to draw shapes int xValues[] = { 245, 245, 260, 260, 230, 230 }; int yValues[] = { 250, 300, 300, 310, 310, 250 }; g.setColor( Color.yellow ); g.fillPolygon ( xValues, yValues, 6 ); // connects the dots

  26. Arrays are lists of numbers int xValues[] = { 245, 245, 260, 260, 230, 230 }; xValue[ 0 ] is 245 xValue[ 1 ] is 245 xValue[ 2 ] is 260 xValue[ 3 ] is 260 xValue[ 4 ] is 230 xValue[ 5 ] is 230

  27. A way of organizing variables int myArray[ ] = { 41, 16, 55, 26, 30, 0 }; myArray is a list of 6 ints The ints are “indexed” 0 thru 5 myArray[ 3 ] is 26 Example: int x = 4; myArray[ x ] is ?

More Related