List<String> chosenPics = new ArrayList<String>();  //zu speichernde ArrayList
SharedPreferences prefs = getSharedPreferences("settings", 0);
Editor edit = prefs.edit();
int count = chosenPics.size();
edit.putInt("count", count);
for(int a = 0; a<count; a++){
     edit.putString("String"+a, chosenPics.get(a));
}
edit.commit();

List<String> sources = new Arraylist<String>();
SharedPreferences prefs = getSharedPreferences("settings", 0);
int count = prefs.getInt("count", 0);
for(int i = 0; i<count; i++){
     sources.add(prefs.getString("String"+i, null));
}