heartdemo.java

《精通JAVA手机游戏与应用程序设计》随书光盘

/*
 * 双缓存显示图片
 */

import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;


public class HeartDemo extends MIDlet implements CommandListener {

	private Command exitCommand;
	private HeartCanvas sg;

	public HeartDemo() {
		exitCommand = new Command("Exit", Command.EXIT, 1);
		sg = new HeartCanvas();
		sg.addCommand(exitCommand);
		sg.setCommandListener(this);
		Display.getDisplay(this).setCurrent(sg);
		
	}
	protected void startApp(){
	}

	protected void pauseApp() {
	}

	protected void destroyApp(boolean arg0){		
	}
	public void commandAction(Command c, Displayable d) {
		if (c == exitCommand) {			
			destroyApp(false);			
			notifyDestroyed();
		}
	}	
}

class HeartCanvas extends Canvas{
	
	Image offScreen;//缓冲区对象
	Graphics drawOffScreen;
	int width,height;
	protected HeartCanvas(){
		try {
			
			//指定缓冲区域为屏幕大小
			width = this.getWidth();
			height = this.getHeight();
			offScreen =Image.createImage(width,height);
			drawOffScreen = offScreen.getGraphics();// 获得一个新的Graphics对象
			drawOffScreen.setColor(0x00f7f7f7);
			drawOffScreen.fillRect(0,0,width,height);
			drawOffScreen.setColor(0x00ee0000);
			int i,j;
			double x,y,r;
			
			for(i=0;i<=90;i++)
				for(j = 0;j <=90;j++){
					
					//转换为直角坐标
					r = Math.PI/45*i*(1-Math.sin(Math.PI/45*j))*18;
					x = r*Math.cos(Math.PI/45*j)*Math.sin(Math.PI/45*i) + width/2;
					y = - r *Math.sin(Math.PI/45*j)+height/4;
					
					drawOffScreen.fillArc((int)x,(int)y-20,1,1,0,360);
					
				}
			
		} catch (Exception e) {			
			e.printStackTrace();
		}					
		
	}
	protected void paint(Graphics g) {		
		//显示缓存区的可变Image对象
		//g.drawImage(offScreen,0,0,Graphics.TOP|Graphics.LEFT);
		
		//drawOffScreen.setColor(0,0,0);
		//int i,j;
		//double x,y,r;
		
		//for(i=0;i<=90;i++)
		//	for(j = 0;j <=90;j++){
				
				//转换为直角坐标
				//r = Math.PI/45*i*(1-Math.sin(Math.PI)/45*j)*18;
				//x = r*Math.cos(Math.PI/45*j)*Math.sin(Math.PI/45+i) + width/2;
				//y = - r *Math.sin(Math.PI/45*j)+height/4;
				
				//drawOffScreen.fillArc((int)x,(int)y,2,2,0,360);
			//	drawOffScreen.fillArc(0,0,2,2,0,360);
		//	}
		g.drawImage(offScreen,0,0,Graphics.TOP|Graphics.LEFT);
		
		
	}
	
}