cocos2dx2.1中android返回键问题

Cocos2d-x
#1 
class LuaGLSurfaceView extends Cocos2dxGLSurfaceView{
	
	public LuaGLSurfaceView(Context context){
		super(context);
	}
	
	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {
    	// exit program when key back is entered
    	if (keyCode == KeyEvent.KEYCODE_BACK) {
    		android.os.Process.killProcess(android.os.Process.myPid());
    	}
        return super.onKeyDown(keyCode, event);
    }
}

2.1版本里面的这个按键触发函数为何无效，是否要设置什么？求高手破解