SDSU Emerging Technology
Fall Semester, 2004
MIDlet UI pt 3
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© 2004, All Rights Reserved, SDSU & Roger Whitney
San Diego State University -- This page last updated 21-Oct-04

CS 683 Emerging Technologies Fall Semester, 2004 Doc 21 MIDlet UI pt 3

Contents

References

Graphics

Example with Attributes

Lines

Rectangle

Translating Origin

What Happens if you Don’t Clear the Screen?

Filling Shapes

Arcs

Text

Some Motion

Clip Regions

Input Events

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.

CS 683 Fall 04Doc 21, MIDlet UI pt 3 Slide # 2

References

J2ME in a Nutshell, Kim Topley, O’Reilly, 2002, Chapter 4

Examples in this lecture are based on examples in the above reference

CS 683 Fall 04Doc 21, MIDlet UI pt 3 Slide # 3

Graphics

Canvas

http://www.eli.sdsu.edu/courses/fall04/cs683/j2me/docs/api/midp/javax/microedition/lcdui/Canvas.html

Graphics

http://www.eli.sdsu.edu/courses/fall04/cs683/j2me/docs/api/midp/javax/microedition/lcdui/Graphics.html

CS 683 Fall 04Doc 21, MIDlet UI pt 3 Slide # 4

Example with Attributes

Based on an example from J2ME in a Nutshell 

import javax.microedition.lcdui.*;
import javax.microedition.midlet.MIDlet;
   
class SampleCanvas extends Canvas
   {
   protected void paint(Graphics g) 
      {
      }
   }
   
public class Attributes extends MIDlet 
   {   
   
   public void startApp() { }
   public void pauseApp() { }
   public void destroyApp( boolean unconditional ) { }

CS 683 Fall 04Doc 21, MIDlet UI pt 3 Slide # 5
   public Attributes()
      {
      Display display = Display.getDisplay(this);
      Canvas canvas = new SampleCanvas();
      
      Form form = new Form("Attributes");
      boolean isColor = display.isColor();
      String colorOrGray = isColor ? "Colors: " : "Grays: ";
      form.append(new StringItem(colorOrGray,
                     String.valueOf(display.numColors())));
   
      form.append(new StringItem("Width: ", 
                     String.valueOf(canvas.getWidth())));
   
      form.append(new StringItem("Height: ", 
                     String.valueOf(canvas.getHeight())));
   
      form.append(new StringItem("Has Pointer? ", 
                     String.valueOf(canvas.hasPointerEvents())));
   
      form.append(new StringItem("MotionEvents? ",
                     String.valueOf(canvas.hasPointerMotionEvents())));
   
      form.append(new StringItem("RepeatEvents? ", 
                     String.valueOf(canvas.hasRepeatEvents())));
   
      form.append(new StringItem("Buffered? ", 
                     String.valueOf(canvas.isDoubleBuffered())));
      display.setCurrent(form);
      }
   }

CS 683 Fall 04Doc 21, MIDlet UI pt 3 Slide # 6

Lines

Based on an example from J2ME in a Nutshell 

import javax.microedition.lcdui.*;
import javax.microedition.midlet.MIDlet;
   
class LineCanvas extends Canvas 
   {
   public void paint(Graphics g) 
      {
      int width = getWidth();
      int height = getHeight();
   
      int black = 0;
      g.setColor(black);
      g.fillRect(0, 0, width, height);
   
      int white = 0xFFFFFF;
      g.setColor(white);
      g.drawLine(0, height/2, width - 1, height/2);
   
      int yellow = 0xFFFF00;
      g.setStrokeStyle(Graphics.DOTTED);
      g.setColor(yellow);
      g.drawLine(0, height/4, width - 1, height/4);
 
      g.setGrayScale(255);
      g.setStrokeStyle(Graphics.SOLID);
      g.drawLine(0, 0, width - 1, height - 1);
      }   
   }

CS 683 Fall 04Doc 21, MIDlet UI pt 3 Slide # 7
public class Lines extends MIDlet 
   {   
   public Lines()
      {
      Display display = Display.getDisplay(this);
      Canvas canvas = new LineCanvas();
      display.setCurrent(canvas);
      }
   
   public void startApp() { }
   public void pauseApp() { }
   public void destroyApp( boolean unconditional ) { }   
   }

CS 683 Fall 04Doc 21, MIDlet UI pt 3 Slide # 8

Rectangle

Based on an example from J2ME in a Nutshell 

class RectanglesCanvas extends Canvas 
   {
   final static int BLACK = 0;
   final static int WHITE = 0xFFFFFF;
   
   public void paint(Graphics g) 
      {
      int width = getWidth();
      int height = getHeight();
   
      g.setColor(WHITE);
      g.fillRect(0, 0, width, height);
      
      g.setColor(BLACK);
      g.drawRect(width/4, 0, width/2, height/4);
            
      g.setStrokeStyle(Graphics.DOTTED);
      g.drawRect(width/4 + 4, 4, width/2 - 8, height/4 - 8);
      
      g.setStrokeStyle(Graphics.SOLID);
      g.drawRoundRect(width/4, height/2, width/2, height/4, 16, 8);
      }
   }

CS 683 Fall 04Doc 21, MIDlet UI pt 3 Slide # 9

Translating Origin 

class TranslateCanvas extends Canvas 
   {
   final static int BLACK = 0;
   final static int WHITE = 0xFFFFFF;
   
   public void paint(Graphics g) 
      {
      int width = getWidth();
      int height = getHeight();
   
      g.setColor(WHITE);
      g.fillRect(0, 0, width, height);
      
      g.setColor(BLACK);
      g.drawRect(0, 0, width/4, height/4);
      g.translate( 15, 15);
      g.drawRect(0, 0, width/4, height/4);
      g.translate( 20, 0);
      g.drawRect(0, 0, width/4, height/4);
   
      //Go back to 0,0 Not needed just to show how to do it
      g.translate(-g.getTranslateX(), -g.getTranslateY());
      }
   }

CS 683 Fall 04Doc 21, MIDlet UI pt 3 Slide # 10

What Happens if you Don’t Clear the Screen? 

class NoClearScreenCanvas extends Canvas 
   {
   final static int BLACK = 0;
   final static int WHITE = 0xFFFFFF;
   
   public void paint(Graphics g) 
      {
      int width = getWidth();
      int height = getHeight();
      
      //Note no code to clear screen
      
      g.setColor(BLACK);
      g.drawRect(0, 0, width/4, height/4);
      g.translate( 15, 15);
      g.drawRect(0, 0, width/4, height/4);
      }
   }

CS 683 Fall 04Doc 21, MIDlet UI pt 3 Slide # 11

Filling Shapes

Based on an example from J2ME in a Nutshell 

class RectangleFillsCanvas extends Canvas 
   {
   final static int BLACK = 0;
   final static int GREEN = 0x00FF00;
   final static int YELLOW = 0xFFFF00;
   
   public void paint(Graphics g) 
      {
      int width = getWidth();
      int height = getHeight();
   
      // Create a black background
      g.setColor(BLACK);
      g.fillRect(0, 0, width, height);
   
      g.setStrokeStyle(Graphics.DOTTED);
      g.setColor(GREEN);
      g.fillRect(width/4, height/4, width/2, height/2);
      g.setColor(YELLOW);
      g.drawRect(width/8, height/8, width/2, height/2);
      }
   }

CS 683 Fall 04Doc 21, MIDlet UI pt 3 Slide # 12

Arcs

Based on an example from J2ME in a Nutshell 

class ArcsCanvas extends Canvas 
   {
   final static int BLACK = 0;
   final static int WHITE = 0xFFFFFF;
   
   public void paint(Graphics g) 
      {
      int width = getWidth();
      int height = getHeight();
   
      g.setColor(BLACK);
      g.fillRect(0, 0, width, height);
   
      // A quarter circle, clockwise 90 degrees
      // from the 3 o'clock position. Show the
      // bounding rectangle as well.
      g.setColor(WHITE);
      g.drawArc(0, 0, width/2, height/2, 0, 90);
   
      // A quarter circle, anticlockwise 90 degrees
      // from the 3 o'clock position. 
      g.setStrokeStyle(Graphics.SOLID);
      g.setColor(WHITE);
      g.drawArc(width/2, 0, width/2, height/2, 0, -90);
      }
   }

CS 683 Fall 04Doc 21, MIDlet UI pt 3 Slide # 13

Text

Based on an example from J2ME in a Nutshell 

class TextCanvas extends Canvas 
   {
   final static int BLACK = 0;
   
   public void paint(Graphics g) 
      {
      int width = getWidth();
      int height = getHeight();
      
      g.setColor(BLACK);
      g.drawString("Top left", 0, 0, Graphics.TOP | Graphics.LEFT);
      
      Font font = g.getFont();
      g.drawString("Below top left", 0, font.getHeight(), 
            Graphics.TOP | Graphics.LEFT);
      
      g.drawString("Bottom right", width, height, 
         Graphics.BOTTOM | Graphics.RIGHT);
      
      String str = "Multi-font ";      
      font = Font.getFont(Font.FACE_PROPORTIONAL, 
            Font.STYLE_UNDERLINED, Font.SIZE_LARGE);
      g.setFont(font);
      g.drawString(str, 0, height/2, 
         Graphics.LEFT | Graphics.BASELINE);
      }
   }

CS 683 Fall 04Doc 21, MIDlet UI pt 3 Slide # 14

Some Motion 

class SimpleMotionCanvas extends Canvas {
   final static int BLACK = 0;
   final static int WHITE = 0xFFFFFF;
   
   int boxX = 0;
   int boxY = 0;
   int boxLength = 25;
   int width = getWidth();
   int height = getHeight();
   Timer timer;
   
   public void paint(Graphics g)  {
      g.setColor(WHITE);
      g.fillRect(0, 0, width, height);
      
      g.setColor(BLACK);
      g.fillRect(boxX, boxY, boxLength, boxLength);
   }
   
   protected void showNotify() {
      startTimer();
   }
   
   protected void hideNotify() {
      stopTimer();
   }

CS 683 Fall 04Doc 21, MIDlet UI pt 3 Slide # 15

Some Motion Continued 

   protected void moveBox() {
      boxX += 5;
      if (boxX > height)
         boxX = 0;
      boxY += 2;
      if (boxY > width)
         boxY = 0;
      repaint();
   }
   
   
   protected void startTimer() {
      timer = new Timer();
      
      TimerTask updateScreen = new TimerTask() {
            public void run() {
               moveBox();
            }
         };
      int frameRate = 10;
      int interval = 1000/frameRate;
      timer.schedule(updateScreen, interval, interval);
   }
   
   protected void stopTimer() {
      timer.cancel();
   }
}

CS 683 Fall 04Doc 21, MIDlet UI pt 3 Slide # 16

Clip Regions 

   protected void moveBox()
      {
      repaint(boxX, boxY, boxLength, boxLength);
      boxX += 5;
      if (boxX > height)
         boxX = 0;
      boxY += 2;
      if (boxY > width)
         boxY = 0;
      repaint(boxX, boxY, boxLength, boxLength);
      }

CS 683 Fall 04Doc 21, MIDlet UI pt 3 Slide # 17

Input Events 

class EventsCanvas extends Canvas 
   {
   
   protected void keyPressed(int keyCode) {
   }
      
   protected void keyRepeated(int keyCode) {
   }
      
   protected void keyReleased(int keyCode) {
   }   
   
   protected void pointerPressed(int x, int y) {
   }
      
   protected void pointerDragged(int x, int y) {
   }
   
   protected void pointerReleased(int x, int y) {
   }

Copyright ©, All rights reserved.

2004 SDSU & Roger Whitney, 5500 Campanile Drive, San Diego, CA 92182-7700 USA.

OpenContent license defines the copyright on this document.

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