SharedPreferences 的 MODE_MULTI_PROCESS 不起作用 [英] MODE_MULTI_PROCESS for SharedPreferences isn't working
问题描述
我有一个 SyncAdapter 在独立于主应用程序进程的自己的进程上运行.
I have a SyncAdapter running on its own process separately from the main app process.
我在我的 SharedPreferences 周围使用了一个静态包装类，它在进程负载(应用程序的 onCreate)上创建一个静态对象，如下所示:
I'm using a static wrapper class around my SharedPreferences that creates a static object on process load (Application's onCreate) like so:
myPrefs = context.getSharedPreferences(MY_FILE_NAME, Context.MODE_MULTI_PROCESS | Context.MODE_PRIVATE);
包装器具有 get 和 set 方法，如下所示:
The wrapper has get and set methods, like so:
public static String getSomeString() {
return myPrefs.getString(SOME_KEY, null);
}
public static void setSomeString(String str) {
myPrefs.edit().putString(SOME_KEY, str).commit();
}
SyncAdapter 和应用程序都使用这个包装类来编辑和获取首选项，这有时有效，但很多时候我看到 SyncAdapter 变旧/缺少首选项在访问首选项时，主应用程序可以正确查看最近的更改.
Both SyncAdapter and app uses this wrapper class to edit and get from the prefs, this works sometimes but a lot of times I see the SyncAdapter getting old/missing prefs on accesses to the prefs, while the main app sees the recent changes properly.
根据文档，我认为 MODE_MULTI_PROCESS 标志应该像我期望的那样工作，允许两个进程看到最新的更改，但它不起作用.
According to the docs I think the MODE_MULTI_PROCESS flag should work as I expect it to, allowing both processes to see latest changes, but it doesn't work.
更新:
根据 x90 的建议，我尝试避免使用静态 SharedPreferences 对象，而是在每个 get/set 上调用 getSharedPreferences方法.这导致了一个新问题，即 prefs 文件在多进程同时访问时被删除 (!!!).即我在 logcat 中看到:
Per x90's suggestion, I've tried refraining from using a static SharedPreferences object and instead calling getSharedPreferences on each get/set method.
This caused a new issue, where the prefs file gets deleted (!!!) on multi-process simultaneous access.
i.e. I see in the logcat:
(process 1): getName => "Name"
(process 2): getName => null
(process 1): getName => null
从那时起，所有保存在 SharedPreferences 对象上的首选项都被删除了.
and from that point all the prefs saved on the SharedPreferences object were deleted.
这可能是我在日志中看到的另一个警告的结果:
This is probably a result of another warning I see in the log:
W/FileUtils(21552): Failed to chmod(/data/data/com.my_company/shared_prefs/prefs_filename.xml): libcore.io.ErrnoException: chmod failed: ENOENT (No such file or directory)
P.S 这不是一个确定性问题，我在发生崩溃后看到了上面的日志，但还无法在同一设备上重新创建，直到现在它似乎还没有在其他设备上发生.
P.S this is not a deterministic issue, I saw the above logs after a crash happened, but couldn't recreate yet on the same device, and until now it didn't seem to happen on other devices.
另一个更新:
我已经为此提交了一个错误报告，在编写了一个小测试方法以确认这确实是一个 Android 问题后，将其标记为 https://code.google.com/p/android/issues/detail?id=66625
I've filed a bug report on this, after writing a small testing method to confirm this is indeed an Android issue, star it at https://code.google.com/p/android/issues/detail?id=66625
推荐答案
遇到了完全相同的问题，我的解决方案是为 SharedPreferences 编写基于 ContentProvider 的替换.它可以 100% 多进程运行.
Had exactly the same problem and my solution was to write a ContentProvider based replacement for the SharedPreferences. It works 100% multiprocess.
我把它变成了我们所有人的图书馆.结果如下:https://github.com/grandcentrix/tray
I made it a library for all of us. Here is the result: https://github.com/grandcentrix/tray
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