jumper_canvas.java

本光盘是《J2ME无线移动游戏开发》一书的配套光盘

package ch08;

import java.io.IOException;
import javax.microedition.lcdui.*;
import javax.microedition.lcdui.game.*;

public class Jumper_Canvas
    extends GameCanvas
    implements Runnable, CommandListener {

  //代表程序是否运行的状态
  boolean running;

  //存储构成动画的各图像帧
  Image img;

  //代表动画的精灵对象
  Sprite sp;

  //屏幕宽度
  int win_width = getWidth();

  //屏幕高度
  int win_height = getHeight();

  //每帧图像的宽度
  int img_width = 32;

  //每帧图像的高度
  int img_height = 48;

  //图像X坐标
  int x;

  //图像Y坐标
  int y;

  //主MIDlet类实例
  Jumper_MIDlet jm;

  /*
   3.构造器
   */
  public Jumper_Canvas(Jumper_MIDlet jm) {
    super(true);
    this.jm = jm;
    Command exitCommand = new Command("退出", Command.EXIT, 0);
    addCommand(exitCommand);
    setCommandListener(this);

    try {
      img = Image.createImage("/icons/cowboy/cowboy.png");
    }
    catch (IOException e) {
      System.out.println(e.getMessage());
    }
    sp = new Sprite(img, img_width, img_height);
    int fs[] = {
        3, 2, 1, 2, 0, 0, 0, 0, 0, 2};
    sp.setFrameSequence(fs);

    sp.defineReferencePixel(img_width / 2, 0);
    x = win_width / 2;
    y = (win_height - img_height) / 2;
    sp.setRefPixelPosition(x, y);
    start();
  }

  /*
   4.启动线程
   */
  public void start() {
    running = true;
    Thread t = new Thread(this);
    t.start();
  }

  /*
   5.控制进程
   */
  public void run() {
    Graphics g = getGraphics();
    long st = 0, et = 0, diff = 0;
    //控制每秒帧数，即动画快慢
    int rate = 250;

    while (running) {
      st = System.currentTimeMillis();
      render(g);
      et = System.currentTimeMillis();
      //避免刷新过快，暂停线程至要求帧数
      diff = et - st;
      if (diff < rate) {
        try {
          Thread.sleep(rate - diff);
        }
        catch (InterruptedException ex) {
          stop();
        }
      }

    }
  }

  /*
   6.实现绘制
   */
  private void render(Graphics g) {

    g.setColor(0x000000);
    g.fillRect(0, 0, win_width, win_height);

    switch (sp.getFrame()) {
      case 5:
        sp.setTransform(Sprite.TRANS_ROT90);
        break;
      case 6:
        sp.setTransform(Sprite.TRANS_ROT180);
        break;
      case 7:
        sp.setTransform(Sprite.TRANS_ROT270);
        break;
      default:
        sp.setTransform(Sprite.TRANS_NONE);
        break;
    }
    sp.nextFrame();
    sp.paint(g);
    //绘制出引用象素点的大致位置
    g.setColor(0x00ff00);
    g.fillArc(x - 2, y - 2, 4, 4, 0, 360);
    flushGraphics();
  }

  /*
   7.结束线程
   */
  public void stop() {
    running = false;
  }

  /*
   8.响应按钮事件
   */
  public void commandAction(Command c, Displayable s) {
    if (c.getCommandType() == Command.EXIT) {
      jm.quitApp();
    }
  }

}