Android 9 Development Cookbook - Third Edition

There's more...

In the Switching between activities recipe from Chapter 1, Activities, we discussed the back stack. Most users would expect the back key to move backward through the "screens" and they don't know or care if those screens are activities or Fragments. Fortunately, Android makes it very easy to add Fragments to the back stack just by adding a call to addToBackStack() before calling commit().

When a Fragment is removed or replaced without adding it to the back stack, it is immediately destroyed. If it is added to the back stack, it is stopped and, if the user returns to the Fragment, it is restarted, instead of recreated.