blocks|key|420499|text|确保您没有多次添加观察者。如果(例如)从视图控制器中的-viewDidLoad或-viewDidAppear调用-addObserver+(因为在应用程序的整个生命周期中可能会多次调用它们)，或者从应用程序委托中的任何应用程序状态回调(-applicationDidBecomeActive、-applicationWillResignActive、-applicationDidEnterBackground、-applicationWillEnterForeground等)，则可能会在您没有意识到的情况下发生这种情况。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|420500|将对-addObserver的调用封装在一个条件中，以确保它只能被调用一次(设置一个标志)，并在其周围放置NSLog语句，以便在多次到达时可以在调试控制台中看到。在代码中搜索您可能忘记的对-addObserver的其他调用。|420501|在添加之前调用-removeObserver，只是为了确保(确保传递与添加时相同的名称和对象)。在一个不存在的观察者上调用-removeObserver是可以的。注意，这更像是一个创可贴，而不是修复-您的代码应该足够智能，知道您是否已经添加了它-但这可能会帮助您诊断问题)。|BOLD|420502|我刚刚写了一个快速的最小测试程序，它添加了一个观察者(一次！)在CNContactStoreDidChangeNotification上，我只在添加或更改联系人时收到一次通知。为你自己写一个类似的测试程序，看看你是否得到了同样的结果。如果您的测试程序工作正常，那么很可能您的应用程序正在做一些您没有预料到的事情(并且多次调用-addObserver+)。|420503|entityMap^0|R|C|14|E|1K|C|3A|R|42|S|4V|U|5Q|V|0|2|C|2M|C|0|7|F|1P|F|29|1K|0|W|Z|4I|C|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|13|8|@$9|14|A|15|B|C]|$9|16|A|17|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|18|8|@$9|19|A|1A|B|C]|$9|1B|A|1C|B|C]|$9|1D|A|1E|B|J]]|D|@]|E|$]]|$1|K|3|L|5|6|7|1F|8|@$9|1G|A|1H|B|C]|$9|1I|A|1J|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|1K|8|@]|D|@]|E|$]]]|N|$]]

Make certain you aren't adding the observer multiple times. This can happen without you realizing it if (for example) you call <code>-addObserver</code> from <code>-viewDidLoad</code> or <code>-viewDidAppear</code> in your view controller (as these might get called more than once throughout the life of your application), or from any of the application state callbacks in your app delegate (<code>-applicationDidBecomeActive</code>, <code>-applicationWillResignActive</code>, <code>-applicationDidEnterBackground</code>, <code>-applicationWillEnterForeground</code>, etc).

Wrap the call to <code>-addObserver</code> in a conditional that ensures it can only be called once (set a flag), and put NSLog statements around it so you can see in the debug console if you are getting there more than once. Search your code for other calls to <code>-addObserver</code> that you might have forgotten about.

Call <code>-removeObserver</code> before adding it, just to be sure (making sure to pass the same name and object as when you added it). Calling <code>-removeObserver</code> on an observer that doesn't exist is okay. Note that this is more of a band-aid than a fix - your code should be smart enough to know whether or not you've already added it - but this might help you diagnose the problem).

I just wrote a quick minimal test program that adds an observer (once!) on <code>CNContactStoreDidChangeNotification</code> and I only get the notification once when I add or change a contact. Write a similar test program for yourself and see if you get the same result. If your test program works correctly, then it is likely that your app is doing something you don't expect (and calling <code>-addObserver</code> multiple times).

blocks|key|849483|text|我遇到了同样的问题，它触发的次数在2到3之间。对我有效的解决方案是设置一个信号量变量，在处理程序中设置，并在完成时重置信号量。将地址簿处理封装在信号量的if语句中，以忽略进一步的调用。在buildFrendsAndContacts中将addressBkSemphore重置为false|type|unstyled|depth|inlineStyleRanges|entityRanges|data|849484|-+(void)addressBkChange:(NSNotification+*)note
{+++
++++if+(addressBkSemphore+==+false)
++++{
++++++++addressBkSemphore+=+TRUE;
++++++++[self+buildFrendsAndContacts];
++++}
}|code-block|syntax|javascript|849485|希望能有所帮助。|849486|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I had the same problem, the number of times it fired varied between 2 &amp; 3. The solution that worked for me was to set a semaphore variable, set in the handler and reset the semaphore when finished. Wrap the address book processing in an if statement on the semaphore to ignore further calls. 
 addressBkSemphore is reset to false in buildFrendsAndContacts

<pre><code>- (void)addressBkChange:(NSNotification *)note
{ 
 if (addressBkSemphore == false)
 {
 addressBkSemphore = TRUE;
 [self buildFrendsAndContacts];
 }
}
</code></pre>

Hope it helps.

blocks|key|429358|text|您可以在几秒钟后启动一次执行计时器或调度，并在这几秒内有新的联系人更新时取消它，从而确保只有由最后一次更新触发的计时器或dispatch_after才会实际执行(考虑到所有更新调用在一秒内一个接一个地到来。差异，就我测试而言)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|429359|顺便说一句，我只能在使用我的应用程序对同一设备上的联系人进行更改时才能重现该问题。如果我更改了链接到同一个apple帐户的另一台设备上的联系人，则只有一次更新。|429360|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

You can start a one time execution timer or a dispatch after few seconds and cancel it in case there's a new contacts update within those seconds, thus ensuring that only the timer or dispatch_after triggered by the last update will actually execute (taking into account that all update calls come one after the other within under a sec. difference, as far as I tested)

And btw, I could reproduce the issue only when making change to contacts on the same device with my app. If I change the contacts on another device linked to the same apple account, there was only one update.

I am able to observe the <code>CNContactStoreDidChangeNotification</code> when the contact database is changed while the app is in background state. I am pretty sure that only one observer was added to <code>NSNotificationCenter</code>.
The problem is <code>NSNotificationCenter</code> posts MULTIPLE times (2, 3, 5, and even more times) even if I only add one new contact. 
Where is the problem?

CNContactStoreDidChangeNotification is fired multiple times

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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当应用程序处于后台状态时，当联系人数据库发生变化时，我可以观察到CNContactStoreDidChangeNotification。我非常确定只有一个观察者被添加到NSNotificationCenter。问题是，即使我只添加了一个新联系人，NSNotificationCenter也会发布多次(2，3，5，甚至更多...

问CNContactStoreDidChangeNotification被多次触发
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