android - Maintain Drag & Dropped items position when restarting -

i have recyclerview - grid, drag & drop, using code i've manage achieve that, , made lot of changes, 1 problem, can't save dragged items position on restarting ( app not phone ). thought adding " int position " item.java constructor, can't getting changed position .

i'm using same drag & drop codes provided in link.

    itemtouchhelper.callback _ithcallback = new itemtouchhelper.callback() {     //and in imlpementaion of     public boolean onmove(recyclerview recyclerview, recyclerview.viewholder viewholder, recyclerview.viewholder target) {         // viewholder's , target's positions in adapter data, swap them         collections.swap(allitems, viewholder.getadapterposition(), target.getadapterposition());         // , notify adapter dataset has changed          rcadapter.notifyitemmoved(viewholder.getadapterposition(), target.getadapterposition());         return true;     }      @override     public void onswiped(recyclerview.viewholder viewholder, int direction) {         //todo     }      //defines enabled move directions in each state (idle, swiping, dragging).     @override     public int getmovementflags(recyclerview recyclerview, recyclerview.viewholder viewholder) {         return makeflag(itemtouchhelper.action_state_drag,                 itemtouchhelper.down | itemtouchhelper.up | itemtouchhelper.start | itemtouchhelper.end);     } }; 

here's code in oncreate :

    itemtouchhelper ith = new itemtouchhelper(_ithcallback);     ith.attachtorecyclerview(rcview); 

getting duplicated items after position changing, code :

    @override public void onstop() {     super.onstop();     sharedpreferencestools.setordereditems(this, allitems); } 

getallitemlist :

private list<item> getallitemlist(){ allitems = sharedpreferencestools.getordereditems(this); //add item .. etc  //return items  

}

just keep modified collection allitems in sharedpreferences , load on app start & store back, once out of app.

to this, need serialize collection json gson , store string. , deserialize afterwards:

public final class sharedpreferencestools {     private static final string user_settings_preferences_name = "usersettings";     private static final string all_items_list = "allitemslist";     private static gson gson = new gsonbuilder().create();      public static list<item> getordereditems(context context) {         string stringvalue = getusersettings(context).getstring(all_items_list, "");         type collectiontype = new typetoken<list<item>>() {         }.gettype();         list<item> result = gson.fromjson(stringvalue, collectiontype);         return (result == null) ? new arraylist<item>() : result;     }      public static void setordereditems(context context, list<item> items) {         string stringvalue = gson.tojson(items);          sharedpreferences sharedpreferences = getusersettings(context);         sharedpreferences.editor editor = sharedpreferences.edit();         editor.putstring(all_items_list, stringvalue);         editor.apply();             }      static sharedpreferences getusersettings(context context) {         return context.getsharedpreferences(user_settings_preferences_name, context.mode_private);     } } 

the usage of these 2 methods:

 sharedpreferencestools.setordereditems(getactivity(), allitems);  ...  list<item> allitems = sharedpreferencestools.getordereditems(getactivity());