Android并发问题
我已经严格分离了 Android 应用程序不同部分之间的层。 在执行的某个时刻，我从 Internet 上的 xml 服务更新我的数据。该更新大约需要 10 秒，并且完全在后台完成 - 这意味着应用程序的用户界面运行良好。然而，对负责数据更新（更新已开始但尚未完成后）的我的类（后来的 DataManager）的进一步调用会使我的应用程序崩溃。对于从不为 null 的对象，会引发 NullPointerException。
因此，我假设一次只有一个线程可以使用我的 DataManager，并且从其他线程调用 DataManager 会导致异常。
我尝试了将“同步”关键字放在敏感方法附近的各种组合，但似乎在执行更新时 - 没有任何东西可以使用我的 DataManager 中的任何内容。
顺便说一句，在执行过程中与 DataManager 相关的其他类似乎也持有空对象。
我想我只是缺少某种用于处理并发问题的设计模式，也许有人可以建议我一些东西？
I have strictly separated the layers between different parts of my Android application.
At some point of execution I am updating my data from xml service on Internet. That updating takes up about 10 seconds and is done completely in the background - meaning the user interface of an application works fine. However further calls to my class (later - DataManager) which is responsible for data updating (after update has been started but not yet finished) makes my application crash. NullPointerException is thrown with objects which NEVER are null.
So I assume that only one Thread can use my DataManager at one time and calls to DataManager from other threads ends up in exceptions.
I tried various combinations of putting 'synchronized' keywords near sensitive methods but it seems that when update is executing - NOTHING can use ANYTHING from my DataManager.
BTW other classes which are related to DataManager during the execution also seem to hold null objects.
I guess I am just missing some kind of design pattern which is used to deal with concurrency problems and maybe anyone can suggest me something?
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由于线程问题，我在使用 Apache http 客户端时遇到了麻烦，我认为您的问题在这方面可能类似。我最终做的是设置一个回调方案。当然，这可能适合你，也可能不适合你。
这对你来说可能有点像鲁布·戈德堡，但它对我有用。
我会让我的 UI 线程使用生成线程来获取数据的方法来调用我的数据管理器对象。该方法的返回值是一个对象，其中最终包含数据。我会让我的活动扩展一个接口，例如“DataCallbackInterface”，并使用线程在获取数据后调用的方法（即 run() 中的最后一行）。由于该调用本质上是在另一个线程中进行的，因此您需要使用 Handler 来运行 DataCallbackInterface 方法的实现中有用的任何内容。当调用该方法时，您将知道数据在那里并且不依赖任何奇怪的同步标志来使其正确。
I had trouble dealing with using the Apache http client because of threading issues and I think your issue could be similar in that respect. What I ended up doing was setting up a callback scheme. This may or may not work for you, of course.
This may seem a bit Rube Goldberg-like to you, but it worked for me.
I would have my UI thread call my data manager object with a method that spawned a thread to go and acquire the data. The method's return value is an object that would EVENTUALLY have the data in it. I would have my activity extend an interface, something like "DataCallbackInterface", with a method that the thread would call after it acquired the data (i.e. the last line in run()). Since that call will inherently be within another thread, you'll need to use a Handler to run anything useful in your implementation of the DataCallbackInterface method. When that method is called, you will know for a fact that the data is there and not rely on any strange synchronization flags to get it right.