android - Store new position of RecyclerView items in SQLite after being dragged and dropped -

i have 2 dimensional arraylist of type string input adapter class of recyclerview. data in list taken sqlite database everytime when onresume() called. have implemented drag , drop feature , onmove() function swaps list elements successfully. however, need store modified list before onresume() called rewrite list , fill old positions. guess implement rewriting functionality within onstop() event. main activity:

recyclerview recyclerview; recyclerviewadapter adapter; recyclerview.layoutmanager layoutmanager;  arraylist<arraylist<string>> data;  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);     toolbar toolbar = (toolbar) findviewbyid(r.id.toolbar);     setsupportactionbar(toolbar);      floatingactionbutton fab = (floatingactionbutton) findviewbyid(r.id.fab);     assert fab != null;     fab.setonclicklistener(new view.onclicklistener() {         @override         public void onclick(view view) {             intent = new intent(mainactivity.this, viewdbactivity.class);             startactivity(i);         }     });      recyclerview = (recyclerview) findviewbyid(r.id.myrecyclerview);     layoutmanager = new linearlayoutmanager(this);     recyclerview.setlayoutmanager(layoutmanager);     recyclerview.itemanimator itemanimator = new defaultitemanimator();      itemtouchhelper item = new itemtouchhelper(new itemtouchhelper.callback() {          @override         public int getmovementflags(recyclerview recyclerview, recyclerview.viewholder viewholder) {             int dragflags = itemtouchhelper.up | itemtouchhelper.down;             int swipeflags = itemtouchhelper.right;             return makemovementflags(dragflags, swipeflags);         }          @override         public boolean onmove(recyclerview recyclerview, recyclerview.viewholder viewholder, recyclerview.viewholder target) {             collections.swap(data, viewholder.getadapterposition(), target.getadapterposition());             adapter.notifyitemmoved(viewholder.getadapterposition(), target.getadapterposition());             return true;         }          @override         public void onmoved(recyclerview recyclerview, recyclerview.viewholder viewholder, int frompos, recyclerview.viewholder target, int topos, int x, int y) {             super.onmoved(recyclerview, viewholder, frompos, target, topos, x, y);             toast.maketext(mainactivity.this, "moved", toast.length_short).show();         }          @override         public void onswiped(recyclerview.viewholder viewholder, int direction) {             data.remove(viewholder.getadapterposition());             adapter.notifyitemremoved(viewholder.getadapterposition());         }     });      item.attachtorecyclerview(recyclerview);     recyclerview.setitemanimator(itemanimator); }  @override protected void onresume() {     super.onresume();      initialize();      if(adapter == null) {         log.v(tag, "adapter = null. initialized");         setadapter();     }     else {         log.v(tag, "notify called");         adapter.updatedata(data);     } }  public void initialize() {     database ourdb = new database(this);     ourdb.opendb();     data = ourdb.getdata();     ourdb.closedb(); }  public void setadapter() {     adapter = new recyclerviewadapter(data, this);     recyclerview.setadapter(adapter); } 

it important update database long know when store data. how can solve problem? suggestions?

!!!

answer:

final solution have implemented:

@override public void onmoved(recyclerview recyclerview, recyclerview.viewholder viewholder, int frompos, recyclerview.viewholder target, int topos, int x, int y) {     super.onmoved(recyclerview, viewholder, frompos, target, topos, x, y);      //preparing new position values     long moveditem = long.parselong(data.get(frompos).get(0));     // .get(frompos).get(0) returns primary key list     long draggeditem = long.parselong(data.get(topos).get(0));      // updating affected rows new orders     database db = new database(mainactivity.this);         db.open();         db.updateorder(draggeditem, topos);         db.updateorder(moveditem, frompos);         db.close(); } 

and inside of db class:

public void updateorder(long rowid, int newpos) {     contentvalues cv = new contentvalues();     cv.put(key_order, newpos);     ourdatabase.update(database_table, cv, key_rowid + "=" + rowid, null); } 

you need field in each db row storing order. need implements features:

• on new row insert (when insert new object in database) need set order field next int. can current max value (with sql function max) , +1

• when user move item in recyclerview, in method onmovedyou must update other rows. can use frompos , topos that. more on below

• when fill recyclerview data need order them order field

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explanation of 2nd feature implemented: need update rows order between frompos , topos:

• if user moved item (for example position 4 2), need to:

  1. get primary key field of current item (using position 4)
  2. change rows between order 2 , order 4: change 2 -> 3 , 3 -> 4
  3. change current item order (using primary key of first point) topos: in example change current item order 2

• if user moved item down (for example position 2 4) need to:

  1. get primary key field of current item (using position 2)
  2. change rows between order 2 , order 4: change 4 -> 3 , 3 -> 2
  3. change current item order (using primary key of first point) topos: in example change current item order 4

hope helps little