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至顶网软件频道基础软件J2ME 2D小游戏入门之游戏的框架

J2ME 2D小游戏入门之游戏的框架

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我们的游戏需要一个通用的游戏框架,也方便以后的开发,但实现一个引擎是复杂的.

作者:favoyang 来源:J2ME开发网 2007年12月28日

关键字: J2ME 游戏 框架

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一、游戏的框架

  我们的游戏需要一个通用的游戏框架,也方便以后的开发,但实现一个引擎是复杂的。作为初学者如果要你考虑太多的问题,恐怕会让你偏离主线,这里只给出canvas的代码,不理解可以参看本站的另外一篇系列文章《使用MIDP2.0开发游戏》。

public class MyGameCanvas extends GameCanvas
 implements Runnable, CommandListener{
  private static MyGameCanvas instance;
  Graphics g;
  boolean running;
  Thread t;
  Command startcmd,exitcmd,restartcmd;
  int keystate;
  boolean keyevent;
  boolean key_up,key_down,key_left,key_right,key_fire;
  private boolean allowinput;
  public int screenwidth;
  public int screenheight;
  boolean gameover;
  //define your variable here
  //define your variable end
  protected MyGameCanvas() {
   super(true);
   g=getGraphics();
   running=false;
   t=null;
   addCommand(startcmd=new Command("start",Command.OK,1));
   addCommand(exitcmd=new Command("exit",Command.EXIT,1));
   setCommandListener(this);
   screenwidth=getWidth();
   screenheight=getHeight();
   //put your init once code here
   //put your init once code end
  }
  synchronized public static MyGameCanvas getInstance() {
   if (instance == null) {
    instance = new MyGameCanvas();
    System.out.println("new MyGameCanvas");
   }
   return instance;
  }
  public void run(){
   System.out.println("MyGameCanvas run start");
   long st=0,et=0,diff=0;
   int rate=50;//16-17 frame per second
   while(running){
    st=System.currentTimeMillis();
    gameinput();
    gameMain();
    et=System.currentTimeMillis();
    diff=et-st;
    if(diff<rate){
     //System.out.println("Sleep "+(rate-diff));
     try {
      Thread.sleep(rate - diff);
     }
     catch (InterruptedException ex) {}
    }else{
     //System.out.println("rush , and the frame using time: "+diff);
    }
   }
   System.out.println("MyGameCanvas run end");
  }
  public void start(){
   if(!running){
    running=true;
    t=new Thread(this);
    t.start();
   }
  }
  private void gameMain() {
   g.setColor(0,0,0);//clear screen
   g.fillRect(0,0,getWidth(),getHeight());
   flushGraphics();
  }
  private void gameInit() {
   gameover=false;
   allowinput=true;
   key_up=key_down=key_left=key_right=key_fire=false;
  }
  public void stop(){
   if(running){
    running = false;
   }
  }
  public void commandAction(Command c, Displayable d) {
   String cmdstr=c.getLabel();
   if(cmdstr.equals("start")){
    gameInit();
    start();
    removeCommand(startcmd);
    addCommand(restartcmd=new Command("restart",Command.OK,1));
   }else if(cmdstr.equals("restart")){
    stop();
    while(t.isAlive());
     gameInit();
    start();
   }else if(cmdstr.equals("exit")){
    stop();
    Navigate.midlet.destroyApp(false);
    Navigate.midlet.notifyDestroyed();
   }
  }
  private void gameinput() {
   if(allowinput){
    keystate=getKeyStates();
    keyevent=false;
    if((keystate & UP_PRESSED)!=0){//up
     key_up=true;keyevent=true;
     //deal your unstop job code here
     //System.out.println("up press");
     //deal your unstop job code end
    }else if((keystate & UP_PRESSED)==0){//release key
     if(key_up==true){
      key_up=false;
      //deal your one press-one job code here
      //System.out.println("up release");
      //deal your one press-one job code end
     }
    }
    if((keystate & DOWN_PRESSED)!=0){//down
     key_down=true;keyevent=true;
     //deal your unstop job code here
     //System.out.println("down press");
     //deal your unstop job code end
    }else if((keystate & DOWN_PRESSED)==0){//release key
     if(key_down==true){
      key_down=false;
      //deal your one press-one job code here
      //System.out.println("down release");
      //deal your one press-one job code end
     }
    }
   if((keystate & LEFT_PRESSED)!=0){//left
    key_left=true;keyevent=true;
    //deal your unstop job code here
    //System.out.println("left press");
    //deal your unstop job code end
   }else if((keystate & LEFT_PRESSED)==0){//release key
    if(key_left==true){
     key_left=false;
     //deal your one press-one job code here
     //System.out.println("left release");
     //deal your one press-one job code end
    }
   }
   if((keystate & RIGHT_PRESSED)!=0){//right
    key_right=true;keyevent=true;
    //deal your unstop job code here
    //System.out.println("right press");
    //deal your unstop job code end
   }else if((keystate & RIGHT_PRESSED)==0){//release key
    if(key_right==true){
     key_right=false;
     //deal your one press-one job code here
     //System.out.println("right release");
     //deal your one press-one job code end
    }
   }
  if((keystate & FIRE_PRESSED)!=0){//fire
   key_fire=true;keyevent=true;
   //deal your unstop job code here
   //System.out.println("fire press");
   //deal your unstop job code end
  }else if((keystate & FIRE_PRESSED)==0){//release key
   if(key_fire==true){
    key_fire=false;
    //deal your one press-one job code here
    //System.out.println("fire release");
    //deal your one press-one job code end
   }
  }
  if(!keyevent){
   //no keyevent here
   //System.out.println("NO KEY press");
   //no keyevent end
  }
 }
}

public static void cleanJob(){
 instance=null;
}

}

  使用singlon实现,因为每个gamecanvas都需要很多的内存空间。另外对我们来说,只要改写gameInit(),gameMain(),一次性初始化的代码写在构造函数中。

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