SharedPreference committed in SyncAdapter not upda

问题:

I am changing and committing a SharedPreference in my SyncAdapter after successful sync, but I am not seeing the updated value when I access the preference in my Activity (rather I am seeing the old value). What am I doing wrong? Different Contexts?

My SyncAdapter where I update the preference:

class SyncAdapter extends AbstractThreadedSyncAdapter {
    private int PARTICIPANT_ID;
    private final Context mContext;
    private final ContentResolver mContentResolver;

    public SyncAdapter(Context context, boolean autoInitialize) {
        super(context, autoInitialize);
        mContext = context;
        mContentResolver = context.getContentResolver();
    }

    public SyncAdapter(Context context, boolean autoInitialize, boolean allowParallelSyncs) {
        super(context, autoInitialize, allowParallelSyncs);
        mContext = context;
        mContentResolver = context.getContentResolver();
    }

    @Override
    public void onPerformSync(Account account, Bundle extras, String authority,
                              ContentProviderClient provider, SyncResult syncResult) {

        final SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(mContext);
        PARTICIPANT_ID = Integer.parseInt(prefs.getString("participant_id", "0"));

        if (success) {
            // save and set the new participant id
            PARTICIPANT_ID = newParticipantId;
            prefs.edit().putString("participant_id", String.valueOf(newParticipantId)).commit();
        }
    }
}

The Service initializing the SyncAdapter with the ApplicationContext:

public class SyncService extends Service {
    private static final Object sSyncAdapterLock = new Object();
    private static SyncAdapter sSyncAdapter = null;

    @Override
    public void onCreate() {
        synchronized (sSyncAdapterLock) {
            if (sSyncAdapter == null) {
                sSyncAdapter = new SyncAdapter(getApplicationContext(), false);
            }
        }
    }

    @Override
    public IBinder onBind(Intent intent) {
        return sSyncAdapter.getSyncAdapterBinder();
    }
}

A static function within the Application called by the Activity that checks the SharedPreference. This does not return the value committed in the SyncAdapter, but the old value. (My SettingsActivity and other Activities also use the old value.):

public static boolean isUserLoggedIn(Context ctx) {
    final SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(ctx);
    int participantId = Integer.parseInt(prefs.getString("participant_id", "0"));
    LOGD("dg_Utils", "isUserLoggedIn.participantId: " + participantId);// TODO
    if (participantId <= 0) {
        ctx.startActivity(new Intent(ctx, LoginActivity.class).addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP));
        return false;
    }
    return true;
}

UPDATE: I am getting the new value when I completely close the app (swipe it from the apps running). I also have a SharedPreferenceChangeListener, which is not fired when the preference is updated.

private final SharedPreferences.OnSharedPreferenceChangeListener mParticipantIDPrefChangeListener = new SharedPreferences.OnSharedPreferenceChangeListener() {
    public void onSharedPreferenceChanged(SharedPreferences prefs, String key) {
        if (key.equals("participant_id")) {
            LOGI(TAG, "participant_id has changed, requesting to restart the loader.");
            mRestartLoader = true;
        }
    }
};

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

    // subscribe to the participant_id change lister
    final SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getActivity());
    PARTICIPANT_ID = Integer.parseInt(prefs.getString("participant_id", "0"));
    prefs.registerOnSharedPreferenceChangeListener(mParticipantIDPrefChangeListener);
}

回答1:

Ok, I figured it out myself with @Titus help and after some research and pieced together a solution for my problem.

The reason why the DefaultSharedPreferences of the same Context are not updated is that I have specified the SyncService to run in its own process in the AndroidManifest.xml (see below). Hence, starting from Android 2.3, the other process is blocked from accessing the updated SharedPreferences file (see this answer and the Android docs on Context.MODE_MULTI_PROCESS).

    <service
        android:name=".sync.SyncService"
        android:exported="true"
        android:process=":sync"
        tools:ignore="ExportedService" >
        <intent-filter>
            <action android:name="android.content.SyncAdapter" />
        </intent-filter>
        <meta-data
            android:name="android.content.SyncAdapter"
            android:resource="@xml/syncadapter" />
    </service>

So I had to set MODE_MULTI_PROCESS when accessing the SharedPreferences both in the SyncAdapter and in the UI process of my app. Because I've used PreferenceManager.getDefaultSharedPreferences(Context) extensively throughout the app I wrote a utility method and replaced all calls of PreferenceManager.getDefaultSharedPreferences(Context) with this method (see below). The default name of the preferences file is hardcoded and derived from the Android source code and this answer.

public static SharedPreferences getDefaultSharedPreferencesMultiProcess(
        Context context) {
    return context.getSharedPreferences(
            context.getPackageName() + "_preferences",
            Context.MODE_PRIVATE | Context.MODE_MULTI_PROCESS);
}

回答2:

Since the SharedPreferences are not process-safe, i wouldn't recommend to use the AbstractThreadedSyncAdapter in another process unless you really need it.

Why do i need multiple processes in my application?

Solution

Remove android:process=":sync" from the Service that you declared in your manifest!

<service
    android:name=".sync.SyncService"
    android:exported="true"
    android:process=":sync"
    tools:ignore="ExportedService" >
    <intent-filter>
        <action android:name="android.content.SyncAdapter" />
    </intent-filter>
    <meta-data
        android:name="android.content.SyncAdapter"
        android:resource="@xml/syncadapter" />
</service>

回答3:

In my case I was trying to access SharedPreferences from a service launched by a BroadcastReceiver.

I removed android:process=":remote" from the declaration in the AndroidManifest.xml to get it to work.

<receiver 
    android:process=":remote" 
    android:name=".Alarm">
</receiver>