How to read other app's SharedPreferences (same user ID)?

Question

Tested on Android 4.3. I have two apps, com.my.app.first and com.my.app.second. In my activity I want to read preferences from the other app. I chose to use the same user ID for both my apps:

android:sharedUserId="com.my.app"

I always load my preferences like this:

prefs = getSharedPreferences("MyAppPreferences", Context.MODE_PRIVATE);

Now, in my second app I do the following:

try {
    Context context = createPackageContext("com.my.app.first", Context.CONTEXT_IGNORE_SECURITY);
    // context.getPackageName() does indeed return "com.my.app.first"

    // Note: Context.MODE_WORLD_READABLE makes no difference here!
    prefs = context.getSharedPreferences("MyAppPreferences", Context.MODE_PRIVATE);
}

prefs.mFile erroneously points to /data/data/com.my.app.second/shared_prefs/MyAppPreferences.xml.

Obviously, the call to getSharedPreferences returns the preferences for the current app even though I used the context of the other app. What am I doing wrong? Please help!

Answer 1

Found the problem! This sure looks like a bug in the getSharedPreferences API. It turned out that a previous call to getSharedPreferences caused the other context.getSharedPreferences() call to return the previous instance - the current app's preferences.

The solution was to make sure that getSharedPreferences() was NOT called before reading the preferences of the other app.