ObjectPreference.java

package com.ponyvillelive.pvlmobile.prefs;

import android.content.SharedPreferences;
import com.google.gson.Gson;
import java.lang.reflect.Type;

public class ObjectPreference<T> {
    private final SharedPreferences preferences;
    private final String key;
    private final Gson gson;
    private final Type type;
    private final T defaultValue;
    private T value;

    public ObjectPreference(SharedPreferences preferences, Gson gson, Class<T> type, String key) {
        this(preferences, gson, type, key, null);
    }

    public ObjectPreference(SharedPreferences preferences, Gson gson, Class<T> type, String key,
                            T defaultValue) {
        this.preferences = preferences;
        this.key = key;
        this.gson = gson;
        this.type = type;
        this.defaultValue = defaultValue;
    }

    public T get() {
        if (value == null) {
            String stringValue = preferences.getString(key, null);
            if (stringValue == null) {
                return defaultValue;
            }
            value = gson.fromJson(stringValue, type);
        }
        return value;
    }

    public boolean isSet() {
        return preferences.contains(key);
    }

    public void set(T value) {
        String stringValue = gson.toJson(value, type);
        preferences.edit().putString(key, stringValue).apply();
        this.value = value;
    }

    public void delete() {
        value = null;
        preferences.edit().remove(key).apply();
    }
}