本例提供一个扫描屏幕的效果展示，其中扫描区域实现了基本的颜色渐变效果。除此之外，程序还包括了GameCanvas和线程的基本适用方法，以及Graphics的绘图操作。
/*
* SweepGame.java
*
* Created on 2005年12月2日, 下午1:25
*/
package com.j2medev.sweep;
import javax.microedition.lcdui.*;
import javax.microedition.lcdui.game.*;
import javax.microedition.midlet.*;
public class SweepGame extends MIDlet {
public void startApp() {
final SweepGameCanvas sweeper = new SweepGameCanvas();
sweeper.start();
sweeper.addCommand(new Command("退出", Command.EXIT, 0));
sweeper.setCommandListener(new CommandListener() {
public void commandAction(Command c, Displayable s) {
sweeper.stop();
notifyDestroyed();
}
});
Display.getDisplay(this).setCurrent(sweeper);
}
public void pauseApp() {}
public void destroyApp(boolean unconditional) {}
}
class SweepGameCanvas extends GameCanvas implements Runnable {
PRivate boolean mTrUCking;
private int mTheta;
private int mBorder;
private int mDelay;
public SweepGameCanvas() {
super(true);
mTheta = 0;
mBorder = 10;
mDelay = 50;
}
public void start() {
mTrucking = true;
Thread t = new Thread(this);t.start();
}
public void stop() {
mTrucking = false;
}
public void render(Graphics g) {
int width = getWidth();
int height = getHeight();
// Clear the Canvas.
g.setGrayScale(255);
g.fillRect(0, 0, width - 1, height - 1);
int x = mBorder;
int y = mBorder;
int w = width - mBorder * 2;
int h = height - mBorder * 2;
for (int i = 0; i < 8; i++) {
g.setGrayScale((8 - i) * 32 - 16);
g.fillArc(x, y, w, h, mTheta + i * 10, 10);
g.fillArc(x, y, w, h, (mTheta + 180) % 360 + i * 10, 10);
}
}
public void run() {
Graphics g = getGraphics();
while (mTrucking) {
mTheta = (mTheta + 1) % 360;
render(g);
flushGraphics();
try { Thread.sleep(mDelay); } catch (InterruptedException ie) {}
}
}
}
（出处：http://www.knowsky.com）
