HeaderGridView | A GridView with the ability to have multiple headers | File Utils library

Code seems fine but I am sure this is not the way to do it,

1. You should null check your arrayList in your activity itself, then proceed to set adapter.

2. For adapter,you should provide activityContext rather than applicationContext, adapters often hold listeners to open activities or to show toasts, it that case it should be activityContext not applicationContext

3. For your problem, I will suggest setting layout manager after setting adapter. In this way, you won't need to call notifyDatasetChang.

Updated part

In your xml, you are adding RecyclerView inside horizontal scrollview which is the reason its giving trouble. Take your recyclerview outside the horizontal scrollview because you are setting the LinearLayoutManager with horizontal orientation in your code anyways. Then set both height and width of the recyclerview to match_parent. Also, if you don't want to add anything else in the footer view, you can remove the linearLayout and set your recyclerview as footer with width=match_parent and height=60dp.

Don't forget to delete horizontalscrollview code.