<me.seewhy.IndexableRecyclerView.IndexableRecyclerView
       android:id="@+id/indexable_recyclerview"
       android:layout_width="match_parent"
       android:layout_height="match_parent"
       app:recyclerColumns="3"/>

List<ItemModel> models = new ArrayList<>();
.
.
.
models.add(new ItemModel("-1", R.mipmap.nh));

IndexableRecyclerViewAdapter indexableRecyclerViewAdapter = new IndexableRecyclerViewAdapter(this, models);
mIndexableRecyclerView.setAdapter(indexableRecyclerViewAdapter);