Baffling recursive ClassCastExceptions when reading Android default shared preferences

Question

Seems like I must be doing something basic very wrong, but the results are strange, and I'm having trouble tracking the problem down.

This is in my my Activity's onCreate()

PreferenceManager.setDefaultValues(this, R.xml.metronome_preferences, false);
mSharedPrefs=PreferenceManager.getDefaultSharedPreferences(this);

The following code lives in onStart().

Map<String,?> map = mSharedPrefs.getAll();
boolean t = mSharedPrefs.contains("tempo_list_pref");
Log.d(logID, "t= " + t + " preferences=" + map.toString());
mBPMOption = mSharedPrefs.getLong("tempo_list_pref", 100);

Log cat correctly shows:

02-05 11:14:27.605: DEBUG/Metronome(16147): t=true preferences={graphics_list_pref=1, conduct_list_pref=12.0f, tempo_list_pref=140, audio_list_pref=2, meter_list_pref=5}

mBPMOption is a long. The shared prefs object is apparently valid as I can both retrieve the preferences as a map, and test for the presence of a preferences, but the call to getLong() causes ClassCastExceptions to be recursively thrown. At least, that's how I'm interpreting what I'm seeing in the debugger. The error object e contains e.cause, e.cause.cause, ... .

I'm getting this same error in the emulator and on the Google ION dev phone.

Any thoughts on this would be appreciated.

Answer 1

it would help if you showed the stack trace, but...

private static final class SharedPreferencesImpl implements SharedPreferences {
    ...
    public long getLong(String key, long defValue) {
        synchronized (this) {
            Long v = (Long) mMap.get(key);
            return v != null ? v : defValue;
        }
    }

10p says your ClassCastException is being thrown there. when the documentation says getLong will throw ClassCastException isn't a Long, it really means it: an int won't do. are you sure you stored this as a long? adding this line to your code will tell you what you've got:

System.err.println(map.get("tempo_list_pref").getClass());