InternalPreferences.java

package org.khanacademy.android.prefs;

import org.khanacademy.core.util.ObservableUtils;

import rx.Observable;
import rx.subjects.PublishSubject;

import android.content.SharedPreferences;

/**
 * Lightweight, internal preferences.
 */
public class InternalPreferences {
    /** The underlying preferences store in the system. */
    private final SharedPreferences mSharedPreferences;

    private PublishSubject<BooleanPreference> mUpdatedBooleanPreferenceSubject;

    public InternalPreferences(SharedPreferences sharedPreferences) {
        mSharedPreferences = sharedPreferences;

        mUpdatedBooleanPreferenceSubject = PublishSubject.create();
    }

    public boolean hasSet(OneTimeMarkerPreference pref) {
        return mSharedPreferences.getBoolean(pref.getKey(), false);
    }

    public boolean markIfUnset(OneTimeMarkerPreference pref) {
        if (!hasSet(pref)) {
            mSharedPreferences.edit().putBoolean(pref.getKey(), true).apply();
            return true;
        }
        return false;
    }

    public boolean getValue(BooleanPreference pref) {
        return mSharedPreferences.getBoolean(pref.getKey(), pref.getDefaultValue());
    }

    public Observable<Boolean> observeValue(final BooleanPreference pref) {
        return ObservableUtils.cache(
                mUpdatedBooleanPreferenceSubject
                        .filter(updatedPref -> updatedPref.getKey().equals(pref.getKey()))
                        .map(unused -> getValue(pref))
                        .distinctUntilChanged(),
                1
        );
    }

    public void setValue(BooleanPreference pref, boolean value) {
        mSharedPreferences.edit().putBoolean(pref.getKey(), value).apply();
        mUpdatedBooleanPreferenceSubject.onNext(pref);
    }
}