Set<String> in android sharedpreferences does not save on force close-ThrowExceptions

Exception or error:

Im trying to use androids sharedpreferences, I´ve logged everything and the code below really commits the string set. The problem is when I force close the app and start again, the settings.getStringSet returns an empty set. No errormessages anywhere.

I´ve tried PreferenceManager.getDefaultSharedPreferences but that does not work for me either.

Thanks for you time.

public static final String PREFS_NAME = "MyPrefsFile";
private static final String FOLLOWED_ROUTES = "followedRoutes";

and later on when saved is called:

public void onFollowClicked(View view){

SharedPreferences settings = getSharedPreferences(PREFS_NAME, MODE_PRIVATE);
SharedPreferences.Editor editor = settings.edit();

Set<String> follows =  settings.getStringSet(FOLLOWED_ROUTES, new HashSet<String>());
follows.add(routeId);

editor.putStringSet(FOLLOWED_ROUTES, follows);
editor.commit();

}
How to solve:

Take a look here.

Also for refference:

SharedPreferences

SharedPreferences.Editor

EDIT:

There’s actually a bug with this one, see here. An extract from there:

This problem is still present on the 17 API level.

It is caused because the getStringSet() method of the
SharedPreferences class doesn’t return a copy of the Set object: it
returns the entire object and, when you add new elements to it, the
commitToMemory method of the SharedPrefencesImpl.EditorImpl class see
that the existing value is equal to the previous one stored.

The ways to workaround this issue is to make a copy of the Set
returned by SharedPreferences.getStringSet or force the write to
memory using other preference that always change (for example, a
property that stores the size of the set each time)

EDIT2:

There might be a solution here, take a look.

###

You can also work around the bug mentioned by g00dy this way:

Get the set from sharedPreferences and save it in a variable.

Then just delete the set in sharedpreferences before adding it again when saving.

SharedPreferences.Editor editor= sharedPref.edit();
editor.remove("mSet");
editor.apply(); 
editor.putStringSet("mSet", mSet);
editor.apply();

Make sure to use apply() or commit() twice.

Alternatively, if you are working in Kotlin simply :

PreferenceManager.getDefaultSharedPreferences(applicationContext)
    .edit {
        this.remove("mSet")
        this.apply()
        this.putStringSet("mSet", mSet)
    }

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