iOS接收远程通知

App在前台或后台的情况下，点击通知栏里的通知会走如下的代理方法：

iOS 10.0之前:

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary
*)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult result))completionHandler{

}

iOS 10.0之后:

- (void)userNotificationCenter:(UNUserNotificationCenter *)center didReceiveNotificationResponse:(UNNotificationResponse
*)response withCompletionHandler:(void(^)())completionHandler{

}