mycanvas.java

这是一个用J2ME编写的在手机上屏幕上移动物体的源代码

import javax.microedition.lcdui.*;

public class MyCanvas extends Canvas {
	
	int x=50,y=50,l=50; //定义全局变量，x,y为矩形起始坐标，l为矩形长宽度
	
	public void paint(Graphics g){
		
		//清除屏幕
		g.setColor(255,255,255);  
		g.fillRect(0,0,getWidth(),getHeight());
		g.setColor(0,0,0);
		
		//绘制矩形
		g.drawRect(x,y,l,l);
				
	}
	
	protected void keyPressed(int keyCode){
		if(getGameAction(keyCode)==UP){     //当点击UP键，矩形向上移动
			y=y-10;
			repaint();
		}
		
		if(getGameAction(keyCode)==DOWN){     //当点击DOWN键，矩形向下移动
			y=y+10;
			repaint();
		}
		
		if(getGameAction(keyCode)==LEFT){     //当点击LEFT键，矩形向左移动
			x=x-10;
			repaint();
		}
		
		if(getGameAction(keyCode)==RIGHT){     //当点击RIGHT键，矩形向右移动
			x=x+10;
			repaint();
		}
		
		if((x+l)<0)x=getWidth();  //判断左溢出

		if(x>getWidth())x=0;  //判断右溢出

		if((y+l)<0)y=getHeight(); //判断上溢出

		if(y>getHeight())y=0; //判断下溢出
		

		
		
	}
	
	
	
	
}