关于J2ME游戏切换屏幕的有关问题，求指导

关于J2ME游戏切换屏幕的问题，求大虾指导~
请问怎么切换屏幕？为什么我的代码不起作用呢？贴代码

public void commandAction(Command c, Displayable d) {
		if(c==cmdbk){
			System.out.println("huiqu22");
			game_state=GAME_STATE_GAMING;
			System.out.println(cmdbk);
			System.out.println("qwqwqwwq");
			
		}else if(c==cmdok){			
			System.out.println("qwqdffdfd");
			game_state=GAME_STATE_MENU;
			
			System.out.println("huiqu");
		}else if(c==backCommand){
			game_state=GAME_STATE_GAMING;
		}
		
	}

下面是主循环

public void run() {
		while(!bQuit){
			//if(flag==true){
			offg.setColor(255,255,255);
			offg.fillRect(0,0,getWidth(),getHeight());
			repaint();
			input();
			 try {
				Thread.currentThread();
				Thread.sleep(80);
			} catch (InterruptedException e) {
				
				e.printStackTrace();
			} 
		}
	}

input函数

public void input(){
		int k=this.getKeyStates();
		switch (game_state) {
		case GAME_STATE_INIT:			
			paintINIT();
			break;
		case GAME_STATE_LOGO:
			paintLOGO();
			break;
		case GAME_STATE_MENU:
			paintMeun();
		break;
		case GAME_STATE_GAMING:			
			switch (game) {
			case GAMING:
				lm.paint(offg,0, 0);
				//检测边界碰撞
				checkBound();
				//检测精灵之间的碰撞
				iscollision();
				//检测Sprite方向
				checkDir(k);
				break;
			}
			case DEP_HR:
				//game_state=GAME_STATE_LOGO;
			break;
		case GAME_STATE_ROLE:
			rolefrm.append(cg);
			rolefrm.addCommand(cmdbk);
			rolefrm.addCommand(cmdok);
			//frm.setCommandListener(this);
			this.m4.dis.setCurrent(rolefrm);
			break;
		case GAME_STATE_HELP:
			paintHelp(offg);

这里有点问题，求指教			break;
		case GAME_STATE_EXIT:			
			exit();			
			break;
		default:
			break;
		}
	}

------解决方案--------------------
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