Question

我已将BackupAgentHelper实施到我的Android应用中。我使用自定义助手备份了几个SharedPreferences文件和我自己的一些实体。

我参与API 22并在真实设备上进行测试（Sony Z3 Compact）。

备份和还原的实体部分工作正常，因为您可以通过它断点并添加日志记录，并按预期写出并回读实体。但是，首选项部分实际上仅在重新启动后更改首选项值。

我在调用super.onRestore之前，在调用super.onRestore之后，在我的代理的onRestore方法中注销了pref值，然后在onRestoreFinished中注销了pref值。值不变。但是，如果我在使用它时重新启动并记录值，它们就是预期的。

我已使用Context.MODE_MULTI_PROCESS标志打开我的日志记录首选项，但它没有任何区别。

其他一些有趣的事情是我注册了一个只记录更改值的OnSharedPreferenceChangeListener，但它永远不会被触发。

我已经看了一段时间了，我已经看过人们在检索错误的偏好值时遇到的各种问题，但他们似乎都指向使用MODE_MULTI_PROCESS标志。我试过了它并没有用。此外，这个标志在API 23中已弃用，因此无论如何看起来都不是长期解决方案。

我的代码如下所示：

public void onCreate()
{
    super.onCreate();

    SharedPreferencesBackupHelper helper = new SharedPreferencesBackupHelper(this, MyApplication.PREFS_A)
    {
        @Override
        public void restoreEntity(BackupDataInputStream data)
        {
            super.restoreEntity(data);
            Logger.debug(FQCN, "Prefs A restore done. Current value A = {0}", getPrefValue("A"));
        }
    };
    addHelper(KEY_PREFS_A, helper);

    SharedPreferencesBackupHelper entityControllerPrefsHelper = new SharedPreferencesBackupHelper(this, MyApplication.PREFS_B)
    {
        @Override
        public void restoreEntity(BackupDataInputStream data)
        {
            super.restoreEntity(data);
            Logger.debug(FQCN, "Prefs B restore done. Current value B = {0}", getPrefValue("B"));
        }
    };

    addEntityHelpers();
}

public void onRestore(BackupDataInput data, int appVersionCode, ParcelFileDescriptor newState) throws IOException
{
    Logger.debug(FQCN, "About to restore. Current value A = {0}", getPrefValue("A"));

    SharedPreferences.OnSharedPreferenceChangeListener listener = new SharedPreferences.OnSharedPreferenceChangeListener()
    {
        @Override
        public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key)
        {
            Logger.stack(FQCN, "onRestore.onSharedPreferenceChanged. Key = {0}, Value = {1}", key, sharedPreferences.getString(key, ""));
        }
    };
    prefs.registerOnSharedPreferenceChangeListener(listener);
    Logger.debug(FQCN, "About to restore. Current value B = {0}", getPrefValue("B"));

    super.onRestore(data, appVersionCode, newState);

    //Just to make sure the listener isn't GC'd while we're restoring.
    Logger.debug(FQCN, "listener hashcode. Not interesting. {0}", listener.hashCode());
}

public void onRestoreFinished()
{
    super.onRestoreFinished();

    Logger.debug(FQCN, "Restore finished. Current value A = {0}", getPrefValue("A"));

    Logger.debug(FQCN, "Restore finished. Current value B = {0}", getPrefValue("B"));
}

public String getPrefValue(String name)
{
    SharedPreferences prefs = MyApplication.get().getSharedPreferences("prefs", Context.MODE_MULTI_PROCESS);
    return prefs.getString(name, "");
}

日志记录就像这样......

Application.onCreate()  Current value A = def
Application.onCreate()  Current value B = uvw

<Backup>
<Uninstall via ADB>
<Install via ADB, following logging comes out when install completes>

D/BackupManagerService: initiateOneRestore packageName=blah
BackupAgentHelper.onRestore()   About to restore. Current value A = abc
BackupAgentHelper.onRestore()   About to restore. Current value B = xyz
SharedPreferencesBackupHelper.restoreEntity()   Prefs A restore done. Current value A = abc
SharedPreferencesBackupHelper.restoreEntity()   Prefs B restore done. Current value B = xyz
BackupAgentHelper.onRestoreFinished()   Restore finished. Current value A = abc
BackupAgentHelper.onRestoreFinished()   Restore finished. Current value B = xyz
I/BackupRestoreController: restoreFinished for 0
I/BackupManagerService: Restore complete.

<Restart>

Application.onCreate()  Current value A = def
Application.onCreate()  Current value B = uvw

Android BackupAgentHelper恢复首选项，但更改在重新启动后才会显示

0 个答案: