Storing a String array in the SharedPreferences

Question

I was wondering if it could be possible to save in the shared preferences an array of Strings, in a way that, every time we save a certain String, we store it in that array.

For example I have a list of locations with a certain ID that I want to mark as favorite. The ideal situation would be, having an array and saving a certain location ID (let's call it Location1) in that array, so next time I want to mark a new location as favorite (let's call it Location2), I retrieve that array (which so far contains Location1) and add the ID of this new location I want to add (Location2).

Android has methods to store primitive objects, but not for arrays. Any idea in order to do this, please?

Answer 1

This is doable: I was just blogging about it:

SAVE YOUR ARRAY

//String array[]
//SharedPreferences prefs
Editor edit = prefs.edit();
edit.putInt("array_size", array.length);
for(int i=0;i<array.length; i++)
    edit.putString("array_" + i, array[i]);
edit.commit();

RETRIEVE YOUR ARRAY

int size = prefs.getInt("array_size", 0);
array = new String[size];
for(int i=0; i<size; i++)
    prefs.getString("array_" + i, null);

---

Just wrote that so there might be typos.

Answer 2

You could make the array a JSON array and then store it like this:

SharedPreferences settings = getSharedPreferences("SETTINGS KEY", 0);
SharedPreferences.Editor editor = settings.edit();

JSONArray jArray = new JSONArray();
try {
    jArray.put(id);
} catch (JSONException e) {
    e.printStackTrace();
}

editor.putString("jArray", jArray.toString());
editor.commit();

You can then get the array like this:

SharedPreferences settings = getSharedPreferences("SETTINGS KEY", 0);
try {
    JSONArray jArray = new JSONArray(settings.getString("jArray", ""));
} catch (JSONException e) {
    e.printStackTrace();
}

Just an alternative solution that I have used in the past