GameAPI

游戏画布，图层和游戏精灵
简介
  javax.microedition.lcdui.game 包,提高Java 游戏的性能
  GameCanvas：游戏画布，比普通画布更加适合游戏开发
  Layer：图层，可以表示画布上的某个可视的物体，是抽象类
  Sprite：可以充当游戏中的具体角色，一般用于运动角色，如子弹，汽车等
  TiledLayer：可以充当游戏中的具体角色，一般用于环境角色，如地图等
  LayerManager：管理图层的变换
GameCanvas
基本结构

classMyGameCanvasextendsGameCanvasimplementsRunnable{
publicMyGameCanvas(){
super(true);
}
publicvoidrun(){
}
}

构造函数传入参数，可以控制特殊键是否被禁用，为true时，可以通过getKeyStates查询状态，一般写法(getKeyStates&相应键值)!=0表示某键

被按下
  可以通过getGraphics直接操作画布，不用写paint函数，不用重画开销，flushGraphics()将缓冲画布画到屏幕上
Sprite
  Layer的子类，Layer中的重要方法：
  int getHeight() /int getWidth()
  int getX() /int getY()
  boolean isVisible() /voidsetVisible(booleanvisible)
  void move(int dx,int dy) /voidsetPosition(intx,inty)
  Sprite(Image image) ：传入一幅图片/Sprite(Image image,int frameWidth,int frameHeight) ：传入图片，设置帧宽度和高度
  Sprite.paint(g)：将精灵画在界面上
Sprite知识点：旋转和悬挂点
  voiddefineReferencePixel(intx,inty) :定义悬挂点
  voidsetRefPixelPosition(intx,inty) ：将悬挂点定位到某个坐标
  int getRefPixelX() ：得到悬挂点的横坐标
  int getRefPixelY() ：得到悬挂点的纵坐标
  voidsetTransform(inttransform) ：旋转
案例：图像不断旋转并且在界面位置不断变化

package prj;

import java.util.Random;

import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Graphics;
import javax.microedition.lcdui.Image;
import javax.microedition.lcdui.game.GameCanvas;
import javax.microedition.lcdui.game.Sprite;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;
//让图片绕着左上角旋转
public class MIDlet6 extends MIDlet {
	private MyGameCanvas mgc = new MyGameCanvas();
	private Display dis;
	protected void startApp() throws MIDletStateChangeException {
		dis = Display.getDisplay(this);
		dis.setCurrent(mgc);

	}
	protected void destroyApp(boolean arg0) throws MIDletStateChangeException {
		

	}

	protected void pauseApp() {
		

	}
	
	class MyGameCanvas extends GameCanvas implements Runnable{
		private boolean RUN = true;
		private Random rnd = new Random();
		private Graphics gra;
		private Sprite s1;
		private Image img;
		private int STATE = Sprite.TRANS_NONE;
		public MyGameCanvas(){
			super(true);
			gra = this.getGraphics();
			try{
				img = Image.createImage("/img1.png");
			}catch(Exception ex){ex.printStackTrace();}
			s1 = new Sprite(img);			
			//定义悬挂点
			//s1.defineReferencePixel(s1.getWidth()/2,s1.getHeight()/2);//坐标是图像上的坐标
			s1.defineReferencePixel(0,0);
			s1.setRefPixelPosition(100,100);//悬挂点在界面上的坐标
			
			new Thread(this).start();
		}		
		public void run(){
			while(RUN){
				try{
					s1.setTransform(STATE);
					gra.setColor(255,255,255);
					gra.fillRect(0,0,this.getWidth(),this.getHeight());
					gra.setColor(255,0,0);
					gra.drawLine(100,100, 150,200);
					s1.paint(gra);
					this.flushGraphics();
					switch(STATE){
					case Sprite.TRANS_NONE: STATE=Sprite.TRANS_ROT90; break;
					case Sprite.TRANS_ROT90: STATE=Sprite.TRANS_ROT180; break;
					case Sprite.TRANS_ROT180: STATE=Sprite.TRANS_ROT270; break;
					case Sprite.TRANS_ROT270: STATE=Sprite.TRANS_NONE; break;
					}					
					Thread.currentThread().sleep(100);
				}catch(Exception ex){}
			}
		}

	}


}

SpriteSprite碰撞检测和动画
Sprite知识点：碰撞检测
  voiddefineCollisionRectangle(intx,inty,intwidth,intheight) ：定义一个矩形的不可碰撞的区域
  boolean collidesWith(Sprite s,boolean pixelLevel)：判断是否和另一个Sprite发生了碰撞；参数2为true，则认为不透明点发生了碰撞才算

碰撞，否则认为矩形发生了碰撞就算碰撞
  boolean collidesWith(TiledLayert,boolean pixelLevel) ：判断是否和TiledLayer发生碰撞，TiledLayer后面会讲
  boolean collidesWith(Image image,intx,inty,boolean pixelLevel)：判断是否和另一个图片碰撞，用的较少，大家可以去查询文档
Sprite知识点：带动画的角色
  能否让一个角色本身就含有动画?
  切割图片原则:首先走行,一行走完,取下一行,编号从0开始
  int getRawFrameCount():得到帧数
  voidnextFrame()/voidprevFrame()/voidsetFrame(int sequenceIndex):设置显示某一帧,号码从0开始算
  voidsetFrameSequence(int[] sequence)/int getFrameSequenceLength() :设置/得到帧的顺序
  int[]seq= newint[]{0,3,2,1};
  voidsetImage(Imageimg,int frameWidth,int frameHeight) :改变图片

package prj;

import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Graphics;
import javax.microedition.lcdui.Image;
import javax.microedition.lcdui.game.GameCanvas;
import javax.microedition.lcdui.game.Sprite;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;

public class MIDlet5 extends MIDlet {
	private MyGameCanvas mgc = new MyGameCanvas();
	private Display dis;
	protected void startApp() throws MIDletStateChangeException {
		dis = Display.getDisplay(this);
		dis.setCurrent(mgc);
	}

	protected void destroyApp(boolean arg0) throws MIDletStateChangeException {
		// TODO Auto-generated method stub

	}

	protected void pauseApp() {
		// TODO Auto-generated method stub

	}
	
	class MyGameCanvas extends GameCanvas implements Runnable{
		private Image img;
		private Sprite sp1;		
		private Graphics gra;
		private boolean RUN = true;
		public MyGameCanvas(){
			super(true);
			try{
				img = Image.createImage("/donghua.png");
				//sp1 = new Sprite(img);
				//你可以将img分割成几个图片小块，每个小块有一定的宽度和高度
				//以下代码将图片分为4帧，
				sp1 = new Sprite(img,img.getWidth()/4,img.getHeight());
				gra = this.getGraphics();
			}catch(Exception ex){
				ex.printStackTrace();
			}
			new Thread(this).start();
		}
		public void run(){
			while(RUN){
				gra.setColor(0,255,0);
				gra.fillRect(0,0,this.getWidth(),this.getHeight());
				sp1.paint(gra);				
				this.flushGraphics();				
				sp1.move(1, 1);
				sp1.nextFrame();
				try{
					Thread.currentThread().sleep(100);
				}catch(Exception ex){}
			}			
		}
	}


}

TiledLayerTiledLayer和图层管理
TiledLayer
  TiledLayer(intcolumns,introws, Image image,int tileWidth,int tileHeight):将图片用tileWidth,tileHeight分割,指定将要填充的列数和

行数,注意,图片小块index从1开始
  以下例子中,左边图片分为2个图片小块,填充右边的地图,四行四列 
TiledLayer
  void paint(Graphics g) :画出TiledLayer
  voidsetCell(int col,introw,int tileIndex) :将某个图片小块填入相应位置
  int getCell(int col,introw) :得到某行某列的图片小块Index
  int getCellHeight() /int getCellWidth()
  int getColumns() /int getRows()
  voidfillCells(int col,introw,int numCols,int numRows,int tileIndex) :用一个图片小块填充整个网格
  voidsetStaticTileSet(Image image,int tileWidth,int tileHeight) :修改图片
实际游戏中的技巧
  应该将不同的物体弄成不同的图层
  右图的地图应该是两个图层:墙壁一个,草地一个,为什么?
  便于碰撞检测
图层管理器：LayerManager
  有一种更好的方法来在界面上画图,不用针对一个个图层来画图了
  void append(Layer l) :添加图层
  void remove(Layer l) ：去掉图层
  voidsetViewWindow(intx,inty,intwidth,intheight) ,设置窗口的可视部分
  void paint(Graphics g,intx,inty),将所有图层画统一画出来

package prj;

import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Graphics;
import javax.microedition.lcdui.Image;
import javax.microedition.lcdui.game.GameCanvas;
import javax.microedition.lcdui.game.LayerManager;
import javax.microedition.lcdui.game.TiledLayer;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;

public class MIDlet6 extends MIDlet {
	private MyGameCanvas mgc = new MyGameCanvas();
	private Display dis;
	protected void startApp() throws MIDletStateChangeException {
		dis = Display.getDisplay(this);
		dis.setCurrent(mgc);
	}
	protected void destroyApp(boolean arg0) throws MIDletStateChangeException {
		// TODO Auto-generated method stub

	}
	protected void pauseApp() {
		// TODO Auto-generated method stub

	}
	
	class MyGameCanvas extends GameCanvas implements Runnable{
		private Image map;
		private TiledLayer tlRoad;
		private TiledLayer tlWall;
		
		private Graphics gra;
		private LayerManager lm;//图层管理器
		private boolean RUN = true;
		private int Y = 0;
		public MyGameCanvas(){
			super(true);
			try{
				map = Image.createImage("/map.png");
				gra = this.getGraphics();
				tlRoad = new TiledLayer(4,4,map,map.getWidth()/2,map.getHeight());
				tlWall = new TiledLayer(4,4,map,map.getWidth()/2,map.getHeight());	
				
				lm = new LayerManager();
				lm.append(tlRoad);
				lm.append(tlWall);
				
				
				int[][] cells = new int[][]{
						{1,2,1,2},
						{1,2,2,2},
						{1,2,1,2},
						{1,2,1,2}
					};
				for(int i=0;i<4;i++){
					for(int j=0;j<4;j++){
						if(cells[j][i]==1){
							tlRoad.setCell(j, i, cells[i][j]);
						}
						else{
							tlWall.setCell(j, i, cells[i][j]);
						}
					}
				}
			}catch(Exception ex){
				ex.printStackTrace();
			}
			new Thread(this).start();
			
		}
		public void run(){
			while(RUN){
				gra.setColor(255,255,255);
				gra.fillRect(0,0,this.getWidth(),this.getHeight());
				//通过LayerManager显示
				lm.setViewWindow(0,Y,80,30);	
				lm.paint(gra, 30,25);	//将图层管理器内的图层画到界面的左上角30,25位置
				this.flushGraphics();
				Y++;
				try{
					Thread.currentThread().sleep(100);
				}catch(Exception ex){}
			}
		}
	}

}