water_canvas.java

本光盘是《J2ME无线移动游戏开发》一书的配套光盘

package ch07;

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

public class Water_Canvas
    extends GameCanvas
    implements Runnable, CommandListener {

  //代表程序是否运行的状态
  boolean running;

  //存储构成背景的各图像帧
  Image img;

  //代表背景
  TiledLayer tlg;

  //水动画播放序列
  int fw[] = {
      6, 7, 8};

  //当前图像帧索引
  int mySequenceIndex = 0;

  //代表水动态背景索引
  int myAnimatedTileIndex;

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

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

  //每帧草图像的宽高
  int img_grass_size = 16;

  //绘制上下文
  Graphics g = getGraphics();

  //主MIDlet类实例
  Water_MIDlet wm;

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

    try {
      img = Image.createImage("/icons/background/field.png");
    }
    catch (IOException e) {
      System.out.println(e.getMessage());
    }
    // 计算横向需要多少图片
    int backcols = win_width / img_grass_size + 1;
    // 计算纵向需要多少图片
    int backrows = win_height / img_grass_size + 1;

    //铺草地
    tlg = new TiledLayer(backcols, backrows, img, img_grass_size,
                         img_grass_size);
    Random r = new Random();
    for (int i = 0; i < backcols * backrows; i++) {
      int n = (r.nextInt() >>> 1) % 5 + 1;
      tlg.setCell(i % backcols, i / backcols, n);
    }

    //铺水区域
    myAnimatedTileIndex = tlg.createAnimatedTile(6);

    //铺外上水区域
    for (int i = 0; i < backcols; i++) {
      tlg.setCell(i, 0, myAnimatedTileIndex);
    }
    //铺外下水区域
    for (int i = 0; i < backcols; i++) {
      tlg.setCell(i, backrows - 2, myAnimatedTileIndex);
      tlg.setCell(i, backrows - 1, myAnimatedTileIndex);
    }
    //铺外左水区域
    for (int i = 0; i < backrows; i++) {
      tlg.setCell(0, i, myAnimatedTileIndex);
    }
    //铺外右水区域
    for (int i = 0; i < backrows; i++) {
      tlg.setCell(backcols - 2, i, myAnimatedTileIndex);
      tlg.setCell(backcols - 1, i, myAnimatedTileIndex);
    }
    //铺内上水区域
    for (int i = 2; i < backcols - 3; i++) {
      tlg.setCell(i, 2, myAnimatedTileIndex);
    }
    //铺内下水区域
    for (int i = 3; i < backcols - 3; i++) {
      tlg.setCell(i, backrows - 4, myAnimatedTileIndex);
    }
    //铺内左水区域
    for (int i = 2; i < backrows - 3; i++) {
      tlg.setCell(2, i, myAnimatedTileIndex);
    }
    //铺内右水区域
    for (int i = 3; i < backrows - 3; i++) {
      tlg.setCell(backcols - 4, i, myAnimatedTileIndex);
    }
    //铺栅栏
    //铺上栅栏
    for (int i = 3; i < backcols - 4; i++) {
      tlg.setCell(i, 3, 9);
    }
    //铺下栅栏
    for (int i = 3; i < backcols - 4; i++) {
      tlg.setCell(i, backrows - 5, 9);
    }
    //铺左栅栏
    for (int i = 3; i < backrows - 4; i++) {
      tlg.setCell(3, i, 9);
    }
    //铺右栅栏
    for (int i = 3; i < backrows - 4; i++) {
      tlg.setCell(backcols - 5, i, 9);
    }

    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() {
    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) {
    //绘制背景
    g.setColor(0x000000);
    g.fillRect(0, 0, win_width, win_height);
    tlg.paint(g);
    mySequenceIndex++;
    mySequenceIndex %= 3;
    tlg.setAnimatedTile(myAnimatedTileIndex, fw[mySequenceIndex]);
    tlg.paint(g);

    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) {
      wm.quitApp();
    }
  }

}