android - GridLayoutManager spanSizeLookup bug -

i having issue gridlayoutmanger setspansizelookup, when orientation of activity changes, changing span count while checking if specific position sort of type, works on orientation change, problem is, i'm using zxing library barcode scanning, whenever button clicked i'm opening zxing default intent , retrieve date it, when zxing opening goes landscape , current activity orientation portrait gives me illegalargumentexception layout manage throws when opening xzing intent, crash log this
java.lang.illegalargumentexception: item @ position 0 requires 2 spans gridlayoutmanager has 1 spans.
problem doesn't occur if rotate phone, happens when launch xzing intent, couldn't figure out how how solve issue bugging me. here spansizelookup -

manager.setspansizelookup(new gridlayoutmanager.spansizelookup() {      @override      public int getspansize(int position) {         return adapter.getholders().get(position).getlabelholder() != null ? getresources().getinteger(r.integer.span) : 1;      } }); 

the span base on screen size can 1-2, 2-3 , 3-4. repeat doesn't give me error on orientation change, error occur when open zxing
p.s if open zxing intent while activity on landspace crash wont occur.

edit

it seems launching zxing default intent causing issue, i'm having activity goes landscape after launches , exception didn't occur, workaround did, created activity handles barcode scanning delay of 1 second launch intent if didn't that, throw same exception.

edit 2

i found that, without setspanspizelookup crash still occurs. calling manager.setspancount(getresources().getinteger(r.integer.span))

here's source code throws exception in gridlayoutmanager.layoutchunk()

final int spansize = getspansize(recycler, state, pos); if (spansize > mspancount) {     throw new illegalargumentexception("item @ position " + pos + " requires " +            spansize + " spans gridlayoutmanager has " + mspancount            + " spans."); } 

is spansize greater spancount? try debug , change spancount , see how works.

---- updated ----

there're couple ways switch between list , grid.

1. only changing spancount.

   you have call layoutmanager.requestlayout() after change spancount. otherwise app may crash.

2. only changing spansizelookup.

   private class customspansize extends gridlayoutmanager.spansizelookup {    private static final int list_span_size = 1;   private static final int grid_span_size = 2;    private int mspansize = list_span_size;    public void aslist() {     mspansize = list_span_size;   }    public void asgrid() {     mspansize = grid_span_size;   }    @override   public int getspansize(int position) {     return mspansize;   } } 

   and use that

   @override protected void oncreate(bundle savedinstancestate) {   super.oncreate(savedinstancestate);   setcontentview(r.layout.activity_main);    mlayoutmanager = new gridlayoutmanager(this, 2);    mcustomspansize = new customspansize();   mlayoutmanager.setspansizelookup(mcustomspansize);   recyclerview recyclerview = (recyclerview) findviewbyid(r.id.recycler);   recyclerview.sethasfixedsize(true);   recyclerview.setlayoutmanager(mlayoutmanager);    ... }  public void somefunction() {   if (changed) {     mcustomspansize.aslist();   } else {     mcustomspansize.asgrid();   }   // use update layout   madapter.notifydatasetchanged();   // or can use update layout   mlayoutmanager.requestlayout(); } 

   this way won't crash forget call notifydatasetchanged or requestlayout