Programming Tutorials

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J2ME Canvas sample to show games programming in J2ME

By: Emiley J. in J2ME Tutorials on 2008年07月07日 [フレーム]

This sample J2ME demonstrates the use of Canvas in a midlet. Most of the graphics methods available are used here to let you quickly learn the concepts of graphics programming in J2ME program. It also shows the basics of creating a J2ME game using the controls of a phone. For example handling the left, right keys and the up, down keys etc.

/*
 * @(#)SampleCanvas.java 1.4 01/06/08
 * Copyright (c) 1999-2001 Sun Microsystems, Inc. All Rights Reserved.
 */
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
class SampleCanvas extends Canvas {
 int x, y; // Location of cross hairs
 String event = ""; // Last key event type
 int keyCode; // Last keyCode pressed
 Font font; // Font used for drawing text
 int fh; // height of the font
 int w, h; // width and height of the canvas
 int titleHeight; // Height of the title
 int pieSize; // Size of the Pie chart used for width and height
 int barSize; // Size of the Bar chart used for width and height
 int eventHeight; // Size of the event region
 int pad; // Padding used between items
 SampleCanvas() {
 w = getWidth();
 h = getHeight();
 font = Font.getFont(Font.FACE_SYSTEM,
	 Font.STYLE_PLAIN, Font.SIZE_SMALL);
 fh = font.getHeight();
 /* Compute the sizes of the bar and pie charts
 * It should use all the space except for the title
	 * and event regions.
 * Don't let the charts get too small
 */
 pad = 2;
 titleHeight = fh + pad * 2;
 eventHeight = fh * 3;
 barSize = h - (titleHeight + pad) - (eventHeight + pad);
 if (barSize < 20) // Don't let them get too small
 barSize = 20;
 if (barSize > (w - pad) / 2) // Shrink to 1/2 width
 barSize = (w - pad) / 2;
 pieSize = barSize;
 }
 protected void keyPressed(int key) {
 keyCode = key;
 event = "Pressed";
 handleActions(key);
 repaint();
 }
 protected void keyRepeated(int key) {
 keyCode = key;
 event = "Repeated";
 handleActions(key);
 repaint();
 }
 protected void keyReleased(int key) {
 keyCode = key;
 event = "Released";
 repaint();
 }
 protected void pointerPressed(int x, int y) {
 this.x = x;
 this.y = y;
 keyCode = 0;
 event = "Pressed";
 repaint();
 }
 protected void pointerReleased(int x, int y) {
 this.x = x;
 this.y = y;
 keyCode = 0;
 event = "Released";
 repaint();
 }
 protected void pointerDragged(int x, int y) {
 this.x = x;
 this.y = y;
 keyCode = 0;
 event = "Dragged";
 }
 void handleActions(int keyCode) {
 int action = getGameAction(keyCode);
 switch (action) {
 case LEFT:
 x -= 1;
 break;
 case RIGHT:
 x += 1;
 break;
 case UP:
 y -= 1;
 break;
 case DOWN:
 y += 1;
 break;
 }
 }
 protected void paint(Graphics g) {
 g.setFont(font);
 g.setGrayScale(255);
 g.fillRect(0, 0, w, h);
 x = (x < 0) ? w - 1 : x;
 y = (y < 0) ? h - 1 : y;
 x = x % w;
 y = y % h;
 // Draw Fill and outline for background of title Text
 int swidth = pad * 2 + font.stringWidth("Pie and Bar Samples");
 int title_x = (w - swidth)/2;
 g.setGrayScale(128);
 g.fillRoundRect(title_x, 0, swidth, fh, 5, 5);
 g.setGrayScale(0);
 g.drawRoundRect(title_x, 0, swidth, fh, 5, 5);
 // Sample Text
 g.setColor(0, 0, 0);
 g.drawString("Pie and Bar Samples", 
	 title_x + pad, pad, Graphics.TOP|Graphics.LEFT);
 // Translate to below title text
 g.translate(0, titleHeight + pad);
 /*
	 * Draw pie chart on the left side
	 * using the barSize for width and height
	 */
 g.setColor(255, 0, 0);
 g.fillArc(0, 0, pieSize, pieSize, 45, 270);
 g.setColor(0, 255, 0);
 g.fillArc(0, 0, pieSize, pieSize, 0, 45);
 g.setColor(0, 0, 255);
 g.fillArc(0, 0, pieSize, pieSize, 0, -45);
 g.setColor(0);
 g.drawArc(0, 0, pieSize, pieSize, 0, 360);
 // Draw Bar chart on right side of the display
 // scale the values to the pieSize maximum value
 int yorig = barSize;
 int h1 = barSize / 3, h2 = barSize / 2, h3 = barSize;
 int avg = (h1 + h2 + h3) / 3;
 // Move over to draw Bar chart
 g.translate((w + pad) / 2, 0);
 int bw = pieSize / 7;
 if (bw < 2)
 bw = 2;
 g.setColor(255, 0, 0);
 g.fillRect(bw*1, yorig-h1, bw+1, h1);
 g.setColor(0, 255, 0);
 g.fillRect(bw*3, yorig-h2, bw+1, h2);
 g.setColor(0, 0, 255);
 g.fillRect(bw*5, yorig-h3, bw+1, h3);
 g.setColor(0);
 g.drawRect(bw*1, yorig-h1, bw, h1);
 g.drawRect(bw*3, yorig-h2, bw, h2);
 g.drawRect(bw*5, yorig-h3, bw, h3);
 // Draw axis for bar chart.
 g.setGrayScale(0);
 g.drawLine(0, 0, 0, yorig);
 g.drawLine(0, yorig, barSize, yorig);
 g.setStrokeStyle(Graphics.DOTTED);
 g.drawLine(0, yorig - avg, barSize, yorig-avg);
 g.setStrokeStyle(Graphics.SOLID);
 // Restore to left and move down
 g.translate(-(w + pad) / 2, pieSize + pad);
 // Draw the key and pointer status
 g.setColor(128, 128, 128);
 int col1 = font.stringWidth("Action:");
 g.drawString("Key: ", col1, 0,
	 Graphics.TOP|Graphics.RIGHT);
 g.drawString(keyString(keyCode), col1, 0,
	 Graphics.TOP|Graphics.LEFT);
 g.drawString("Action:", col1, fh,
	 Graphics.TOP|Graphics.RIGHT);
 g.drawString(actionString(keyCode), col1, fh,
	 Graphics.TOP|Graphics.LEFT);
 g.drawString("Event:", col1, fh*2,
	 Graphics.TOP|Graphics.RIGHT);
 g.drawString(event, col1, fh*2,
	 Graphics.TOP|Graphics.LEFT);
 int col2 = 80;
 g.drawString("x:", col2, 0,
	 Graphics.TOP|Graphics.RIGHT);
 g.drawString(Integer.toString(x), col2, 0,
	 Graphics.TOP|Graphics.LEFT);
 g.drawString("y:", col2, fh,
	 Graphics.TOP|Graphics.RIGHT);
 g.drawString(Integer.toString(y), col2, fh,
	 Graphics.TOP|Graphics.LEFT);
 // Restore the origin and draw the crosshairs on top
 g.translate(-g.getTranslateX(), -g.getTranslateY());
 g.setColor(0, 0, 0);
 g.drawLine(x, y - 5, x, y + 5);
 g.drawLine(x - 5, y, x + 5, y);
 }
 
 String keyString(int keyCode) {
 if (keyCode == 0) {
 return "";
 }
 return Integer.toString(keyCode);
 }
 String actionString(int keyCode) {
 if (keyCode == 0) {
 return "";
 }
 int action = getGameAction(keyCode);
	switch (action) {
	case FIRE:
	 return "Fire";
	case LEFT:
	 return "Left";
	case RIGHT:
	 return "Right";
	case DOWN:
	 return "Down";
	case UP:
	 return "Up";
	case GAME_A:
	 return "Game A";
	case GAME_B:
	 return "Game B";
	case GAME_C:
	 return "Game C";
	case GAME_D:
	 return "Game D";
	case 0:
	 return "";
	default:
	 return Integer.toString(action);
	}
 }
}

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