Recyclerview make the last added item be the selected item?

Question

I have a horizontal Recyclerview which displays bitmaps. The Way it is implemented is I have a Imageview and a recyclerview underneath it. The currently selected item is displayed on the image view. The selected image view is given a blue background to indicate it is selected. I can choose images from the gallery and each time a new image is selected, I want to scroll to the last position and make the item selected.

The list of images is maintained in a array list and each time a new image is added, I add the image to the list and notifyDataChanged().

Currently when I am binding a view, I toggle the visibility of the blue background in

public void onBindViewHolder(final MyRecyclerViewHolder holder, int position) { }

But the problem is, if the child is off screen, the bind view is not called and I dont scroll to the new position. I read through the documentation of recycler view and could not figure out how to scroll to that particular child view. I do not there is a SmoothScrollTo method but my question is where do I trigger this ?

Answer 1

There is one solution:

1. In your RecyclerView adapter, add a variable selectedItem and a methods setSelectedItem():

   private static int selectedItem = -1;
   
    ... ...
   
   public void setSelectedItem(int position)
   {
      selectedItem = position;
   }
   

2. In your onBindViewHolder(...), add:

   @Override
   public void onBindViewHolder(ViewHolder holder, final int position) 
   {
      ... ...
   
      if(selectedItem == position)
         holder.itemView.setSelected(true);
   }   
   

3. Now you can scroll to specific item and set it selected programmatically by:

   myRecyclerViewAdapter.setSelectedItem(position_scrollTo);
   myRecyclerView.scrollToPosition(position_scrollTo);
   

For example, you want to scroll to last position and make it selected, just:

    int last_pos = myRecyclerViewAdapter.getItemCount() - 1;
    myRecyclerViewAdapter.setSelectedItem(last_pos);
    myRecyclerView.scrollToPosition(last_pos);

[UPDATE]

To add item and make it selected, you should have a addItem(...) method in adapter, which will add item to item list. After adding item, refresh list and scroll to new added/latest item:

myRecyclerViewAdapter.addItem(...);
myRecyclerViewAdapter.notifyDataSetChanged();
myRecyclerViewAdapter.setSelectedItem(myRecyclerViewAdapter.getItemCount() - 1); 
myRecyclerView.scrollToPosition(myRecyclerViewAdapter.getItemCount() - 1);

Hope this help!