Stick header recyclerView fixed header

Question

I’m implementing the effect of stick header in a recyclerView in my app. I created a subclass of RecyclerView.ItemDecorator and made my implementation, the effect was applied to Recycler, however the headers are disappearing from the screen before the next header reaches the top, I researched how I can do this and made some changes to the code, but still continues with the same problem. Can you give me a hint as to how I can make a header of mine RecyclerView only exit the top of the screen when the next header reaches the top?