判断是否存在的代码：

  private static boolean c(Activity paramActivity)

  {

    List localList = ((ActivityManager)paramActivity.getSystemService("activity")).getRunningTasks(1);

    return (localList.size() > 0) &&              ("com.rytong.egbank".equals(((ActivityManager.RunningTaskInfo)localList.get(0)).topActivity.getPackageName()));

  }

需要增加权限：<uses-permission android:name="android.permission.GET_TASKS" />