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I'm adding a new layout to RecycleView on click of a plus button of the previous layout. At first, I'm adding empty data to model class and setting the adapter with one item. After that click of the button, I need to add the second item and so on.

Problem is . at first it works and recyclview with one item is display. on click of button second layout is also added below first. but a third time if I click on that button. it is adding a new item to the top of Recycleview. I need to generate a vertical hierarchy.

Adding First Data on onCreate

var arrayList:ArrayList<SubjectModel> = ArrayList()

 var model = SubjectModel()
 arrayList.add(model)

 var adapter = SubjectListAdapter(arrayList)

 var layoutManager = LinearLayoutManager(this,LinearLayoutManager.VERTICAL,false)

 rv_subject.layoutManager = layoutManager
 rv_subject.adapter = adapter

And inside the adapter. I have a plus button which is adding new item vertically.

 holder.img_delete_subject.setTag(position);
 holder.img_delete_subject.setOnClickListener(new View.OnClickListener() 
 @Override
 public void onClick(View view) 


 if (if it is plus ) 

 holder.img_delete_subject.setImageResource(minus image);

 data.add(data.size(),new SubjectModel());
 notifyItemInserted((data.size() - 1));

 else 

 data.remove(Integer.parseInt(view.getTag().toString()));
 notifyItemRemoved(Integer.parseInt(view.getTag().toString()));

 


 
 );

The problem is with notifiyDataSetChanged(). As documentation says:

 * <p>This event does not specify what about the data set has changed, forcing
 * any observers to assume that all existing items and structure may no longer be valid.
 * LayoutManagers will be forced to fully rebind and relayout all visible views.</p>

When you add single item to the list, you should be using

notifyItemInsterted(position: Int)

 /**
 * Notify any registered observers that the item reflected at <code>position</code>
 * has been newly inserted. The item previously at <code>position</code> is now at
 * position <code>position + 1</code>.
 *
 * <p>This is a structural change event. Representations of other existing items in the
 * data set are still considered up to date and will not be rebound, though their
 * positions may be altered.</p>
 *
 * @param position Position of the newly inserted item in the data set