java - How to save List<Object> to SharedPreferences?

Question

I have a list of products, which i retrieve from webservice, when app is opened for first time, app gets product list from webservice. I want to save this list to shared preferences.

    List<Product> medicineList = new ArrayList<Product>();

where Product class is:

public class Product {
    public final String productName;
    public final String price;
    public final String content;
    public final String imageUrl;

    public Product(String productName, String price, String content, String imageUrl) {
        this.productName = productName;
        this.price = price;
        this.content = content;
        this.imageUrl = imageUrl;
    }
}

how i can save this List not requesting from webservice each time?

Answer 1

It only possible to use primitive types because preference keep in memory. But what you can use is serialize your types with Gson into json and put string into preferences:

private static SharedPreferences sharedPreferences = context.getSharedPreferences(STORE_FILE_NAME, Context.MODE_PRIVATE);

private static SharedPreferences.Editor editor = sharedPreferences.edit();

public <T> void setList(String key, List<T> list) {
    Gson gson = new Gson();
    String json = gson.toJson(list);

    set(key, json);
}

public static void set(String key, String value) {
    editor.putString(key, value);
    editor.commit();
}

Extra Shot from below comment by @StevenTB

To Retrive

 publicList<YourModel> getList(){
    List<YourModel> arrayItems;
    String serializedObject = sharedPreferences.getString(KEY_PREFS, null); 
    if (serializedObject != null) {
         Gson gson = new Gson();
         Type type = new TypeToken<List<YourModel>>(){}.getType();
         arrayItems = gson.fromJson(serializedObject, type);
     }
}