SharedPrefsSavable

SharedPrefsSavable.java

import android.content.Context;
import android.content.SharedPreferences;
import android.util.Log;
import com.google.gson.Gson;

/** A base class which will allow your class to be Json-serialized to a private SharedPreferences storage.
 */
public class SharedPrefsSavable {
    /** True if the object was created from scratch this session */
    private transient boolean mIsNew;

    /** Loads and deserializes user preferences of type "type" */
    public static <T extends SharedPrefsSavable> T load(Class type, Context context) {
        T userData = null;
        try {
            String stringData = loadRaw(type, context);
            if (stringData != null) {
                userData = (T) new Gson().fromJson(stringData, type);
            }
        }
        catch (Exception ex)
        {
            Log.e("SharedPrefsSavable", ex.getMessage());
        }

        if (userData == null) {
            try {
                userData = (T) type.newInstance();
                ((SharedPrefsSavable) userData).mIsNew = true;
            }
            catch (Exception ex) {
                throw new RuntimeException(ex);
            }
        }
        return userData;
    }

    public void save(Context context) {
        String prefsKey = getPrefsKey(context);
        SharedPreferences prefs = context.getSharedPreferences(prefsKey, Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = prefs.edit();
        String asString = new Gson().toJson(this);
        String objectKey = getPreferencesId();
        editor.putString(objectKey, asString);
        editor.commit();
    }

    private static String getPrefsKey(Context context) {
        return context.getPackageName();
    }

    private static String getPreferencesId(Class<? extends SharedPrefsSavable> type) {
        return type.getName();
    }

    public String getPreferencesId() {
        return SharedPrefsSavable.getPreferencesId(this.getClass());
    }

    /** Fetches the stored user preferences from local storage and returns raw string data. */
    public static String loadRaw(Class type, Context context) {
        String prefsKey = getPrefsKey(context);
        SharedPreferences prefs = context.getSharedPreferences(prefsKey, Context.MODE_PRIVATE);
        String key = getPreferencesId(type);
        String stringData = prefs.getString(key, null);
        return stringData;
    }

    /** True if the object was created from scratch this session */
    public boolean isNew() {
        return mIsNew;
    }
}