Diffutil in recycleview, making it autoscroll if a new item is added

Question

If we use DiffUtil.Callback, and do

adapter.setItems(itemList);
diff.dispatchUpdatesTo(adapter);

how can we make sure that ad

Answer 1

You have a dispatchUpdatesTo(ListUpdateCallback) method to use as well.

So you could just implement a ListUpdateCallback which gives you the first element inserted

class MyCallback implements ListUpdateCallback {
    int firstInsert = -1;
    Adapter adapter = null;
    void bind(Adapter adapter) {
        this.adapter = adapter;
    }
    public void onChanged(int position, int count, Object payload) {
        adapter.notifyItemRangeChanged(position, count, payload);
    }
    public void onInserted(int position, int count) {
        if (firstInsert == -1 || firstInsert > position) {
            firstInsert = position;
        }
        adapter.notifyItemRangeInserted(position, count);
    }
    public void onMoved(int fromPosition, int toPosition) {
        adapter.notifyItemMoved(fromPosition, toPosition);
    }
    public void onRemoved(int position, int count) {
        adapter.notifyItemRangeRemoved(position, count);
    }
}

and then just scroll the RecyclerView manually

myCallback.bind(adapter)
adapter.setItems(itemList);
diff.dispatchUpdatesTo(myCallback);
recycler.smoothScrollToPosition(myCallback.firstInsert);