关于StackOverflow的第一个问题，我将问一下Google Cloud Messaging服务，特别是Loopback的实现。 
 
 所以，我正在开发一个应用程序，并开始在不同的分支上工作，介绍Loopback的推送通知处理，以及REST Api的各种工具。 即使这个主题将严格涵盖Loopback处理GCM的方式，但问题也与Google文档中描述的原始方式有关。 
 
 因此，GCM启动背后的主要思想是检查设备是否已注册。 
 
 这是通过简单检查SharedPreferences变量来完成的，该变量是用于存储我们的RegistrationID值的名称。 
 
final LocalInstallation installation = new LocalInstallation(context, adapter);
 
 如果找到，则设备必须通知服务器，并传送令牌。 否则，必须完成GCM的注册。 完成此操作后，设备会通知服务器。 （ registerInBackground(installation)最终会在检索RegistrationId后调用saveInstallation(installation) ） 
 
    if (installation.getDeviceToken() != null) {
        saveInstallation(installation);
    } else {
        registerInBackground(installation);
    }
 
 如果通信成功，设备将使用SharedPreferences保存RegistrationId，如上所述。 （注意：getDeviceToken（）是Loopback通过API处理SharedPreferences中的值的方法） 
 
 假设每次创建MainActivity时都会执行“GCM-Check”（因此，在onCreate方法期间）。 
 
 我们也知道GCM有时候很乱，想要刷新我的应用程序的RegistrationId或其他一些东西，说实话，我现在还不完全清楚。 简而言之，GCM使我的应用程序的令牌无效。 当服务器使用绑定到我的设备应用程序的令牌发送推送通知时，这会导致错误消息。 
 
 类似的错误 
 
{"multicast_id":0123456789012345678,"success":0,"failure":1,"canonical_ids":0,"results":[{"error":"NotRegistered"}]}
 
 您可以看到"failure":1和"results":[{"error":"NotRegistered"}] 
 
 正如谷歌文档所说，环回通过让服务器删除链接到有缺陷的RegistrationId的设备的记录来做出反应。 可理解。 
 
 回到我们的设备。 再次启动我的应用程序并加载MainActivity会导致相同的“GCM检查”过程。 这次app可以使用SharedPreferences找到RegistrationId，并且可以直接通知服务器，服务器使用给定的RegistrationId创建记录。 
 
 设备应用程序不会处理新的注册。 
 
 你可以在这里看到循环。 设备将不知道它的令牌无效，并将继续告诉服务器相同的数据，这将继续向错误的registrationId发送信息，从而在收到相关错误后将其删除。 
 
 问题是应用程序必须依赖于一次创建但永远不会被修改的数据。 要删除旧数据，我应该向设备发送通知，这显然是不可能的，因为我无法从GCM到达它。 其他可能的解决方案是通过发送电子邮件或短信通知用户，并要求他点击一个按钮，但我宁愿采用更“自动化”的方法解决问题。 
 
 
 我发现了一个非常糟糕的解决方案 
 
 据我所知，在推送通知期间，唯一的错误信息从GCM返回到服务器，我在设备上做了一些小问题。 
 
 这个想法很简单：使用我的服务器应该使用的头进行身份验证，向GCM服务器创建一个POST请求。 这会导致错误被赋予设备本身，它可以解析JSON并注意发生了什么。 从这里，该应用程序可以打造一个新的注册过程，解决问题。 
 
 这有什么不好的？ 事实上，要将设备作为服务器进行身份验证，我必须对ServerKey进行硬编码并将其分发到每个应用程序中。 ServerKey应该只在服务器上使用，这使得这个解决方案成为一个非常糟糕的主意。 
 
 
 这就是说，简单地让设备使用SharedPreference值知道其状态的想法并不是那么好，因为它只会告诉我是否至少注册过一次，而不让我知道我当前的状态。 
 
 在我开发的其他使用GCM的应用程序中，我已经用不同的方式解决了，例如让用户点击按钮或阅读服务器发送的一些特殊短信，然后启用GoogleCloudMessaging.unregister（）起初，最后是GoogleCloudMessaging.register（） 
 
 
 那么，请求原谅这样的文本墙，你是如何解决这个NotRegistered的事情的？ 
 
 感谢您的努力和阅读时间，并希望在回答:) 

for my first question on StackOverflow I'm gonna ask about Google Cloud Messaging service, and in particular Loopback's implementation.
 
So, I'm developing an app and started to work on a different branch to introduce Loopback's push notification handling and it's various tools for REST Api. Even if this topic is gonna cover strictly Loopback's way to handle GCM, the question is also related to the original way as is described on Google docs.
 
So, the main idea behind GCM's kick-off is to check whether the device is registered or not.
 
This is done by a simple check on a SharedPreferences variable, a name used to store our RegistrationID value.
 
final LocalInstallation installation = new LocalInstallation(context, adapter);
 
If this is found, the device has to notify the server, communicating the token. Else, a registration to GCM has to be done. Once this is done, the device notifies the server. ( registerInBackground(installation) will eventually call saveInstallation(installation) after retrieving RegistrationId )
 
    if (installation.getDeviceToken() != null) {
        saveInstallation(installation);
    } else {
        registerInBackground(installation);
    }
 
If communication is successful, the device saves RegistrationId using SharedPreferences as described above. (NOTE : getDeviceToken() is Loopback's way to handle via API the value in SharedPreferences)
 
Let's say this "GCM-Check" is being done every time my MainActivity is being created (so, during the onCreate method).
 
We also know GCM is sometimes messy, and wants to refresh my app's RegistrationId or some other stuff that, to be honest, is not completely clear to me right now. In short terms, GCM invalidates the token of my app. This causes an error-message when the server send a push-notification using the Token bound to my device-app. 
 
An error similar to 
 
{"multicast_id":0123456789012345678,"success":0,"failure":1,"canonical_ids":0,"results":[{"error":"NotRegistered"}]}
 
You can see, "failure":1 and "results":[{"error":"NotRegistered"}]
 
Loopback reacts just as Google docs say, by having the server remove the record of the device linked to the faulty RegistrationId . Comprehensible.
 
Back to our device. Launching my app again and loading MainActivity, causes the same "GCM-check" procedure. This time the app can find RegistrationId using SharedPreferences, and can directly notify the server, which creates a record with the given RegistrationId. 
 
No new registration is being handled by the device-app.
 
You can see the loop in here. Device will have no knowledge of it's token invalidity and will continue to tell the server the same data, which will keep sending information to the wrong registrationId, thus removing it after receiving the related error. 
 
The problem is that the app has to rely on data which is created once and never gets modified. To remove the old data I should send a notification to the device, which is obviously not possible as I can't reach it from GCM. Other solutions possible is notify the user by sending an email or sms, and ask him to click a button for example, but I'd rather have a more "automated" approach to the problem.
 
 
A VERY BAD SOLUTION I'VE FOUND
 
As to my knowledge the only error-info is returned from GCM to the server during a push-notification, I've made a little hack on the device.
 
The idea is simple: create a POST request to GCM Servers, using the headers my server should use to authenticate. This causes the error to be given to the device itself, which can parse the JSON and notice what happened. From here the app can forge a new registration process, fixing the issue.
 
What is bad about this? The fact that to authenticate the device as the server, I have to hard-code the ServerKey and distribute it in every app. The ServerKey should be used only on the server, making this solution a very bad idea.
 
 
This being said, the idea of simply letting the device know its state using a SharedPreference value is not so great, as it would only tell me if I ever registered at least once, without letting me know my current status.
 
On other apps I've developed which use GCM just as well, I've solved in different ways, like having a Button to be clicked by the user or reading some specials SMS send by the server, which then enable GoogleCloudMessaging.unregister() at first and eventually GoogleCloudMessaging.register()
 
 
So, asking for forgiveness for such a wall-of-text, how have you solved this NotRegistered thing?
 
Thanks for your effort and time in reading and, hopefully, in answering : )

原文：https://stackoverflow.com/questions/28945783