Stick header recyclerView fixed header

I am implementing the effect of stick header on a recyclerView in my application. I created a subclass of RecyclerView.ItemDecorator and did 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 code changes , but still continues with the same problem. Can you give me a hint how can I make a header of my RecyclerView just exit the top of the screen when the next header arrives at the top?