本例演示了如何使用Canvas和Timer来制作动画效果，可以使用Guage来调节帧速率和动画精灵的个数。程序结构清晰，是不错的参考案例。

/*
 * AnimationMIDlet.java
 *
 * Created on 2005年12月2日, 上午10:50
 */

package com.j2medev.animation;

import java.util.Timer;
import java.util.TimerTask;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.MIDlet;

public class AnimationMIDlet extends MIDlet implements CommandListener, ItemStateListener {
   
    // The MIDlet's Display object
    private Display display;
    // Flag indicating first call of startApp
    protected boolean started;
    // Exit command
    private Command exitCommand;
    // Setup command
    private Command setupCommand;
    // Run command
    private Command runCommand;
    // Configuration form
    private Form form;
    // Animation canvas
    private AnimationCanvas canvas;
    // Gauge for block count
    private Gauge blockGauge;
    // Gauge for frame rate
    private Gauge rateGauge;
    // Initial frame rate
    private static final int FRAME_RATE = 1;
    // Initial number of blocks
    private static final int BLOCK_COUNT = 1;
   
    protected void startApp() {
        if (!started) {
            display = Display.getDisplay(this);
            form = new Form("Animation");
            rateGauge = new Gauge("Frame rate", true, 10, FRAME_RATE);
            blockGauge = new Gauge("Blocks", true, 4, BLOCK_COUNT);
            form.append(rateGauge);
            form.append(blockGauge);
            form.setItemStateListener(this);
            canvas = createAnimationCanvas();
            exitCommand = new Command("Exit", Command.EXIT, 0);
            setupCommand = new Command("Setup", Command.SCREEN, 0);
            runCommand = new Command("Run", Command.SCREEN, 0);
            canvas.addCommand(exitCommand);
            canvas.addCommand(setupCommand);
            form.addCommand(exitCommand);
            form.addCommand(runCommand);
            form.setCommandListener(this);
            canvas.setCommandListener(this);
            display.setCurrent(form);
            started = true;
        }
    }
   
    protected void pauseApp() {
    }
   
    protected void destroyApp(boolean unconditional) {
    }
   
    public void commandAction(Command c, Displayable d) {
        if (c == exitCommand) {
            notifyDestroyed();
        } else if (c == runCommand) {
            display.setCurrent(canvas);
        } else if (c == setupCommand) {
            display.setCurrent(form);
        }
    }
    public void itemStateChanged(Item item) {
        if (item == blockGauge) {
            int count = blockGauge.getValue();
            if (count < 1) {
                count = 1;
            }
            canvas.setBlockCount(count);
        } else if (item == rateGauge) {
            int count = rateGauge.getValue();
            if (count < 1) {
                count = 1;
            }
            canvas.setFrameRate(count);
        }
    }
    // Creates the canvas that will draw the block
    protected AnimationCanvas createAnimationCanvas() {
        return new AnimationCanvas();
    }
    class AnimationCanvas extends Canvas {
       
        // Size of each block
        protected static final int SIZE = 6;
        // Initial speeds in the X direction
        protected final int[] xSpeeds = { 2, -2, 0, -2 };
        // Initial speeds in the Y direction
        protected final int[] ySpeeds = { 2, -2, 2, -0 };
        // Background color
        protected int background = display.isColor() ? 0xff0ff0 : 0xc0c0c0;
        // Foreground color
        protected int foreground = display.isColor() ? 0xfff000 : 0;
        // Width of screen
        protected int width = getWidth();
        // Height of screen
        protected int height = getHeight();
        // The screen update rate
        protected int frameRate;
        // The blocks to draw on the screen
        protected Block[] blocks;
        // The update timer
        protected Timer timer;
        // The update timer task
        protected TimerTask updateTask;
        // Gets the maximum number of blocks
        public int getMaxBlocks() {
            return blocks.length;
        }
        // Constructs a canvas with default settings
        AnimationCanvas() {
            setBlockCount(BLOCK_COUNT);
            setFrameRate(FRAME_RATE);
        }
        // Sets the number of blocks to draw
        public void setBlockCount(int count) {
            if (count > xSpeeds.length) {
                throw new IllegalArgumentException("Cannot have more than "
                        + xSpeeds.length + " blocks");
            }
            blocks = new Block[count];
            createBlocks();
        }
        // Gets the number of blocks to draw
        public int getBlockCount() {
            return blocks.length;
        }
        // Sets the number of updates per second
        public void setFrameRate(int frameRate) {
            if (frameRate < 1 || frameRate > 10) {
                throw new IllegalArgumentException("Frame rate must be > 0 and <= 10");
            }
            this.frameRate = frameRate;
            if (isShown()) {
                startFrameTimer();
            }
        }
        // Gets the number of updates per second
        public int getFrameRate() {
            return frameRate;
        }
        // Paint canvas background and all
        // of the blocks in their correct locations.
        protected void paint(Graphics g) {
            // Paint with the background color
            g.setColor(background);
            g.fillRect(0, 0, width, height);
            // Draw all of the blocks
            g.setColor(foreground);
            synchronized (this) {
                for (int i = 0, count = blocks.length; i < count; i++) {
                    g.fillRect(blocks[i].x, blocks[i].y, SIZE, SIZE);
                }
            }
        }
        // Notification that the canvas has been made visible
        protected void showNotify() {
            // Start the frame timer running
            startFrameTimer();
        }
        // Notification that the can