blocks|key|965993|text|如果有人正在处理类似的设计问题，并且需要在多个安卓设备之间同步更改，我推荐使用Google+Cloud+Messaging+for+Android。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|965994|我正在研究一种解决方案，其中在一个客户端上所做的更改必须传播到其他客户端。我刚刚实现了一个概念验证实现(服务器&客户端)，它的工作方式非常出色。|965995|基本上，每个客户端都将增量更改发送到服务器。例如，资源id+ABCD1234已从值100变为99。|965996|服务器根据其数据库验证这些增量更改，然后批准更改(客户端处于同步状态)并更新其数据库，或者拒绝更改(客户端不同步)。|965997|如果变更被服务器批准，则服务器通过GCM通知其他客户端(不包括发送增量变更的客户端)，并发送携带相同增量变更的组播消息。客户端处理此消息并更新其数据库。|965998|很酷的是，这些更改几乎是瞬间传播的！如果这些设备在线的话。而且我不需要在这些客户端上实现任何轮询机制。|965999|请记住，如果设备离线时间太长，并且GCM队列中等待传递的消息超过100条，则GCM将丢弃这些消息，并在设备恢复在线时发送一条特殊消息。在这种情况下，客户端必须与服务器进行完全同步。|966000|也可以检查this+tutorial，开始使用CGM客户端实现。|966001|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.android.com/google/gcm/index.html|1|http://hmkcode.com/android-google-cloud-messaging-tutorial/^0|13|Y|0|0|0|0|0|0|0|0|5|D|1|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@$A|12|B|13|1|14]]|C|$]]|$1|D|3|E|5|6|7|15|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|16|8|@]|9|@]|C|$]]|$1|H|3|I|5|6|7|17|8|@]|9|@]|C|$]]|$1|J|3|K|5|6|7|18|8|@]|9|@]|C|$]]|$1|L|3|M|5|6|7|19|8|@]|9|@]|C|$]]|$1|N|3|O|5|6|7|1A|8|@]|9|@]|C|$]]|$1|P|3|Q|5|6|7|1B|8|@]|9|@$A|1C|B|1D|1|1E]]|C|$]]|$1|R|3|-4|5|6|7|1F|8|@]|9|@]|C|$]]]|S|$T|$5|U|V|W|C|$X|Y]]|Z|$5|U|V|W|C|$X|10]]]]

If anyone is dealing with similar design issue and needs to synchronize changes across multiple Android devices I recommend checking <a href="http://developer.android.com/google/gcm/index.html" rel="noreferrer">Google Cloud Messaging for Android</a> (GCM).

I am working on one solution where changes done on one client must be propagated to other clients. And I just implemented a proof of concept implementation (server &amp; client) and it works like a charm.

Basically, each client sends delta changes to the server. E.g. resource id ABCD1234 has changed from value 100 to 99.

Server validates these delta changes against its database and either approves the change (client is in sync) and updates its database or rejects the change (client is out of sync).

If the change is approved by the server, server then notifies other clients (excluding the one who sent the delta change) via GCM and sends multicast message carrying the same delta change. Clients process this message and updates their database.

Cool thing is that these changes are propagated almost instantaneously!!! if those devices are online. And I do not need to implement any polling mechanism on those clients.

Keep in mind that if a device is offline too long and there is more than 100 messages waiting in GCM queue for delivery, GCM will discard those message and will send a special message when the devices gets back online. In that case the client must do a full sync with server.

Check also <a href="http://hmkcode.com/android-google-cloud-messaging-tutorial/" rel="noreferrer">this tutorial</a> to get started with CGM client implementation.

blocks|key|1180301|text|这回答了使用Xamarin框架的开发人员(请参阅https://stackoverflow.com/questions/40156342/sync-online-offline-data)|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1180302|使用xamarin框架实现这一点的一个非常简单的方法是使用Azure的离线数据同步，因为它允许按需从服务器推送和拉取数据。读操作在本地完成，写操作按需推送；如果网络连接中断，写操作将排队，直到连接恢复，然后执行。|1180303|实现相当简单：|1180304|1)在azure门户中创建移动应用(您可以在https://tryappservice.azure.com/这里免费试用)|1180305|2)将您的客户端连接到移动应用。https://azure.microsoft.com/en-us/documentation/articles/app-service-mobile-xamarin-forms-get-started/|1180306|3)设置本地存储库的代码：|1180307|const+string+path+=+"localrepository.db";

//Create+our+azure+mobile+app+client
this.MobileService+=+new+MobileServiceClient("the+api+address+as+setup+on+Mobile+app+services+in+azure");

//setup+our+local+sqlite+store+and+initialize+a+table
var+repository+=+new+MobileServiceSQLiteStore(path);

//+initialize+a+Foo+table
store.DefineTable<Foo>();

//+init+repository+synchronisation
await+this.MobileService.SyncContext.InitializeAsync(repository);
var+fooTable+=+this.MobileService.GetSyncTable<Foo>();|code-block|syntax|javascript|1180308|4)然后推送和拉取您的数据，以确保我们拥有最新的更改：|1180309|await+this.MobileService.SyncContext.PushAsync();
await+this.saleItemsTable.PullAsync("allFoos",+fooTable.CreateQuery());|1180310|https://azure.microsoft.com/en-us/documentation/articles/app-service-mobile-xamarin-forms-get-started-offline-data/|1180311|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/40156342/sync-online-offline-data|1|https://tryappservice.azure.com/|2|https://azure.microsoft.com/en-us/documentation/articles/app-service-mobile-xamarin-forms-get-started/|3^0|O|1X|0|0|0|0|M|W|1|0|G|2U|2|0|0|0|0|0|0|37|3|0^^$0|@$1|2|3|4|5|6|7|1B|8|@]|9|@$A|1C|B|1D|1|1E]]|C|$]]|$1|D|3|E|5|6|7|1F|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|1G|8|@]|9|@]|C|$]]|$1|H|3|I|5|6|7|1H|8|@]|9|@$A|1I|B|1J|1|1K]]|C|$]]|$1|J|3|K|5|6|7|1L|8|@]|9|@$A|1M|B|1N|1|1O]]|C|$]]|$1|L|3|M|5|6|7|1P|8|@]|9|@]|C|$]]|$1|N|3|O|5|P|7|1Q|8|@]|9|@]|C|$Q|R]]|$1|S|3|T|5|6|7|1R|8|@]|9|@]|C|$]]|$1|U|3|V|5|P|7|1S|8|@]|9|@]|C|$Q|R]]|$1|W|3|X|5|6|7|1T|8|@]|9|@$A|1U|B|1V|1|1W]]|C|$]]|$1|Y|3|-4|5|6|7|1X|8|@]|9|@]|C|$]]]|Z|$10|$5|11|12|13|C|$14|15]]|16|$5|11|12|13|C|$14|17]]|18|$5|11|12|13|C|$14|19]]|1A|$5|11|12|13|C|$14|X]]]]

this answers developers who are using the Xamarin framework (see <a href="https://stackoverflow.com/questions/40156342/sync-online-offline-data">https://stackoverflow.com/questions/40156342/sync-online-offline-data</a>)

A very simple way to achieve this with the xamarin framework is to use the Azure’s Offline Data Sync as it allows to push and pull data from the server on demand. Read operations are done locally, and write operations are pushed on demand; If the network connection breaks, the write operations are queued until the connection is restored, then executed.

The implementation is rather simple:

1) create a Mobile app in azure portal (you can try it for free here <a href="https://tryappservice.azure.com/" rel="nofollow noreferrer">https://tryappservice.azure.com/</a>)

2) connect your client to the mobile app.
<a href="https://azure.microsoft.com/en-us/documentation/articles/app-service-mobile-xamarin-forms-get-started/" rel="nofollow noreferrer">https://azure.microsoft.com/en-us/documentation/articles/app-service-mobile-xamarin-forms-get-started/</a>

3) the code to setup your local repository:

<pre><code>const string path = "localrepository.db";

//Create our azure mobile app client
this.MobileService = new MobileServiceClient("the api address as setup on Mobile app services in azure");

//setup our local sqlite store and initialize a table
var repository = new MobileServiceSQLiteStore(path);

// initialize a Foo table
store.DefineTable&lt;Foo&gt;();

// init repository synchronisation
await this.MobileService.SyncContext.InitializeAsync(repository);
var fooTable = this.MobileService.GetSyncTable&lt;Foo&gt;();
</code></pre>

4) then to push and pull your data to ensure we have the latest changes:

<pre><code>await this.MobileService.SyncContext.PushAsync();
await this.saleItemsTable.PullAsync("allFoos", fooTable.CreateQuery());
</code></pre>

<a href="https://azure.microsoft.com/en-us/documentation/articles/app-service-mobile-xamarin-forms-get-started-offline-data/" rel="nofollow noreferrer">https://azure.microsoft.com/en-us/documentation/articles/app-service-mobile-xamarin-forms-get-started-offline-data/</a>

blocks|key|1180393|text|我建议你也看看Symmetricds。它是一个可用于安卓系统的SQLite复制库。您可以使用它来同步您的客户端和服务器数据库，我还建议在服务器上为每个客户端设置单独的数据库。尝试在一个mysql数据库中保存所有用户的数据并不总是最好的主意。特别是当用户数据将快速增长时。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1180394|entityMap|0|LINK|mutability|MUTABLE|url|http://www.symmetricds.org/^0|7|B|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

I suggest you also take a look at <a href="http://www.symmetricds.org/" rel="nofollow noreferrer">Symmetricds</a>. it is a SQLite replication library available to android systems. you can use it to synchronize your client and server database, I also suggest to have separate databases on server for each client. Trying to hold the data of all users in one mysql database is not always the best idea. Specially if the user data is going to grow fast.

I'm looking for some general strategies for synchronizing data on a central server with client applications that are not always online.

In my particular case, I have an android phone application with an sqlite database and a PHP web application with a MySQL database. 

Users will be able to add and edit information on the phone application and on the web application. I need to make sure that changes made one place are reflected everywhere even when the phone is not able to immediately communicate with the server.

I am not concerned with how to transfer data from the phone to the server or vice versa. I'm mentioning my particular technologies only because I cannot use, for example, the replication features available to MySQL.

I know that the client-server data synchronization problem has been around for a long, long time and would like information - articles, books, advice, etc - about patterns for handling the problem. I'd like to know about general strategies for dealing with synchronization to compare strengths, weaknesses and trade-offs.

Synchronizing client-server databases

数据同步

SQL数据库

数据库

服务器

Xamarin

SQLite

MySQL

我正在寻找一些通用策略，用于将中央服务器上的数据与并非总是在线的客户端应用程序同步。在我的特殊情况下，我有一个带有sqlite数据库的android phone应用程序和一个带有MySQL数据库的phone应用程序。用户将能够在电话应用程序和web应用程序上添加和编辑信息。我需要确保在一个地方所做的更改在所有地方都能反...

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