Emerging Technology Fall Semester, 2004 An Example
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CS 683 Emerging Technologies Fall Semester, 2004 Doc 24 An Example

Contents

References

Graphics Example

Copyright ©, All rights reserved. 2004 SDSU & Roger Whitney, 5500 Campanile Drive, San Diego, CA 92182-7700 USA. OpenContent ( http://www.opencontent.org/opl.shtml) license defines the copyright on this document.

References

J2ME in a Nutshell, Kim Topley, O’Reilly, 2002, chapter 5

Correction for Doc 21 slide 16

   public void paint(Graphics g) 
      {
      System.out.println("paint");
      int clipX = g.getClipX();
      int clipY = g.getClipY();
      int clipWidth = g.getClipWidth();
      int clipHeight = g.getClipHeight();
   
      g.setColor(WHITE);
      g.fillRect(clipX, clipY, clipWidth, clipHeight);
      
      g.setColor(BLACK);
      g.fillRect(boxX, boxY, boxLength, boxLength);
      }
   
   protected void moveBox()
      {
      System.out.println("First repaint");
      repaint(boxX, boxY, boxLength, boxLength);
      boxX += 5;
      if (boxX > height)
         boxX = 0;
      boxY += 2;
      if (boxY > width)
         boxY = 0;
      System.out.println("Second repaint");
      repaint(boxX, boxY, boxLength, boxLength);
      }
   
CS 683 Fall 04
Doc 24, An Example Slide # 4

Graphics Example

This example is from code provided with J2ME in a Nutshell, Kim Topley, 2002, O’Reilly

package ora.ch5;
   
import javax.microedition.lcdui.Canvas;
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Font;
import javax.microedition.lcdui.Graphics;
import javax.microedition.lcdui.List;
import javax.microedition.midlet.MIDlet;
   
public class GraphicsMIDlet extends MIDlet implements CommandListener {
   
   // The MIDlet's Display object
   private Display display;
      
   // Flag indicating first call of startApp
   protected boolean started;
   
   // Exit command
   private Command exitCommand;
   
   // Back to examples list command
   private Command backCommand;
   
   // The example selection list
   private List examplesList;

   // The Canvases used to demonstrate different Items
   private Canvas[] canvases;
   
   // The example names. Used to populate the list.
   private String[] examples = {
      "Lines", "Rectangles", "RectangleFills",
      "Arcs", "FilledArcs", "Text"
   };
   
   protected void startApp() {
      if (!started) {
         started = true;
         display = Display.getDisplay(this);
         
         // Create the common commands
         createCommands();
         
         // Create the canvases
         createCanvases();
         
         // Create the list of examples
         createList();
         
         // Start with the List
         display.setCurrent(examplesList);
      }
   }
   
   protected void pauseApp() {
   }
   
   protected void destroyApp(boolean unconditional) {
   }

   public void commandAction(Command c, Displayable d) {
      if (d == examplesList) {
         // New example selected
         int index = examplesList.getSelectedIndex();
         display.setCurrent(canvases[index]);
      } else if (c == exitCommand) {
         // Exit. No need to call destroyApp
         // because it is empty.
         notifyDestroyed();
      } else if (c == backCommand) {
         // Go back to main selection list
         display.setCurrent(examplesList);
      }
   }
   
   private void createCommands() {
      exitCommand = new Command("Exit", Command.EXIT, 0);
      backCommand = new Command("Back", Command.BACK, 1);
   }
   
   private void createList() {
      examplesList = new List("Select Example", List.IMPLICIT);
      for (int i = 0; i < examples.length; i++) {
         examplesList.append(examples[i], null);
      } 
      examplesList.setCommandListener(this);
   }

   private void createCanvases() {
      canvases = new Canvas[examples.length];
      canvases[0] = createLinesCanvas();
      canvases[1] = createRectanglesCanvas();
      canvases[2] = createRectangleFillsCanvas();
      canvases[3] = createArcsCanvas();
      canvases[4] = createFilledArcsCanvas();
      canvases[5] = createTextCanvas();
      
   }
   
   private void addCommands(Displayable d) {
      d.addCommand(exitCommand);
      d.addCommand(backCommand);
      d.setCommandListener(this);
   }
   
   // Create the Canvas for the line drawing example
   private Canvas createLinesCanvas() {
      Canvas canvas = new LineCanvas();      
      addCommands(canvas);
      return canvas;
   }   
      
   // Create the Canvas for the rectangles example
   private Canvas createRectanglesCanvas() {
      Canvas canvas = new RectanglesCanvas();      
      addCommands(canvas);
      return canvas;
   }

   // Create the Canvas for the filled rectangles example
   private Canvas createRectangleFillsCanvas() {
      Canvas canvas = new RectangleFillsCanvas();      
      addCommands(canvas);
      return canvas;
   }
      
   // Create the Canvas for the arcs example
   private Canvas createArcsCanvas() {
      Canvas canvas = new ArcsCanvas();      
      addCommands(canvas);
      return canvas;
   }
         
   // Create the Canvas for the filled arcs example
   private Canvas createFilledArcsCanvas() {
      Canvas canvas = new FilledArcsCanvas();      
      addCommands(canvas);
      return canvas;
   }   
            
   // Create the Canvas for the text example
   private Canvas createTextCanvas() {
      Canvas canvas = new TextCanvas();
      addCommands(canvas);
      return canvas;
   }
   
}

// A canvas that illustrates line drawing
class LineCanvas extends Canvas {
   public void paint(Graphics g) {
      int width = getWidth();
      int height = getHeight();
   
      // Fill the background using black
      g.setColor(0);
      g.fillRect(0, 0, width, height);
   
      // White horizontal line
      g.setColor(0xFFFFFF);
      g.drawLine(0, height/2, width - 1, height/2);
   
      // Yellow dotted horizontal line
      g.setStrokeStyle(Graphics.DOTTED);
      g.setColor(0xFFFF00);
      g.drawLine(0, height/4, width - 1, height/4);
   
      // Solid diagonal line in brightest gray
      g.setGrayScale(255);
      g.setStrokeStyle(Graphics.SOLID);
      g.drawLine(0, 0, width - 1, height - 1);
   }   
}

Rest of the Canvas classes not shown

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