I'm designing an android app with a long list, on which I'm implementing a 'back to top' action. My first go-to was a floating action button, but I'm wondering if I can use some other widget or some other kind of interface(action) that is intuitive. I checked out Google's Material Design but there isn't anything specific. Is there some better UI/UX for this function that is usually done?
Floating arrow button pointing "UP" when you pass a certain scroll height seems to be the standard way.
That behaviour is also used quite a lot in chat/messenger apps, especially when there are new messages and you have to scroll down to find them.
If you have long content a back-to-top link can prove useful. However, for normal content, users will usually scroll using the scrollbar and they often scroll at the top to gain access to the menu.
If you want to omit a "back-to-top" button I would suggest making your navigation/header fixed so at any point your users can navigate through the app with ease.
You can read more about 'back to top' and other in-page links on the NN/G website.