Android应用中怎么判断服务是否运行

/** 
 * 
 * 
 * @param mContext 
 * @param serviceName 
 *      是包名+服务的类名（例如：net.loonggg.testbackstage.TestService） 
 * @return true代表正在运行，false代表服务没有正在运行 
 */ 
public boolean isServiceWork(Context mContext, String serviceName) { 
  boolean isWork = false; 
  ActivityManager myAM = (ActivityManager) mContext 
      .getSystemService(Context.ACTIVITY_SERVICE); 
  List<RunningServiceInfo> myList = myAM.getRunningServices(40); 
  if (myList.size() <= 0) { 
    return false; 
  } 
  for (int i = 0; i < myList.size(); i++) { 
    String mName = myList.get(i).service.getClassName().toString(); 
    if (mName.equals(serviceName)) { 
      isWork = true; 
      break; 
    } 
  } 
  return isWork; 
}