movegamecanvas.java

《Java程序设计实践教程》代码

/***************************************************
*  程序文件名称：　MoveGameCanvas.java
*  功能：控制物体移动
***************************************************/

import javax.microedition.lcdui.*; 
import javax.microedition.lcdui.game.*; 

public class MoveGameCanvas extends GameCanvas implements Runnable { 
　// Game Loop runs when isPlay is true 
  private boolean isPlay; 
　 // 定义休眠常数 
  private long delay;
　 // 设置颜色块的坐标
  private int currentX, currentY; 
　 // 设置屏幕宽度
  private int width; 
　// 设置屏幕高度
  private int height;  
          
　 // 初始化
  public MoveGameCanvas() { 
    super(true); 
    width = getWidth(); 
    height = getHeight(); 
    currentX = width / 2; 
    currentY = height / 2; 
    delay = 20; 
   } 

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

public void stop() { 
  isPlay = false; 
 } 

// 游戏线程
public void run() { 
  Graphics g = getGraphics(); 
  while (isPlay == true) { 
     //键盘事件
	 input(); 
     //绘制图形
	 drawScreen(g); 
     try  {  Thread.sleep(delay);}
     catch (InterruptedException ie) { } 
   } 
 } 

// 用户键盘按钮事件
private void input() { 
  int keyStates = getKeyStates(); 
   // Left 
  if ((keyStates & LEFT_PRESSED) != 0) 
     currentX = Math.max(0, currentX - 1); 
  // Right 
  if ((keyStates & RIGHT_PRESSED) != 0) 
     if (currentX + 5 < width) 
         currentX = Math.min(width, currentX + 1); 
   // Up 
  if ((keyStates & UP_PRESSED) != 0) 
     currentY = Math.max(0, currentY - 1); 
  // Down 
  if ((keyStates & DOWN_PRESSED) != 0) 
     if (currentY + 10 < height) 
       currentY = Math.min(height, currentY + 1); 
 } 

// 绘制图形 
private void drawScreen(Graphics g) { 
  //设置背景色为淡蓝色
  g.setColor(0,255,255);   
  g.fillRect(0,0,getWidth(),getHeight());
　//设置当前坐标系统
　g.translate(currentX-g.getTranslateX(),currentY-g.getTranslateY());
　g.setColor(0x00000000);
　 //在当前坐标系统中绘制
　g.fillRect(2,2,22,22); 
　 //设置移动物体的颜色(红色)
　g.setColor(0x00ff0000);
　g.fillRect(0,0,20,20);
	//刷新画面
  flushGraphics(); 
 } 
}