I've been struggling with this problem for like a week, it's basically a Backstack problem I didn't found an optimal solution yet. I am working on a project which's flow is like this:
Activity (Fragment_A -> Fragment_B -> Fragment_C -> Fragment_A)
I am setting on Fragment_A one DatePicker and a TimePicker and I have 2 TextViews that redirect the user to Fragment_B. From Fragment_B I send some data to Fragment_C that converts the data and sends it back to Fragment_A.
The problem is that as far as I've understood is that when going back to Fragment_A it goes with a new instance, not the old, so my data there is lost. I resolved for now with sharedPreferences but it seems too complicated for a solution. I've tried with custom beginTransaction() and Navigation component but it didn't turn out well.
I was close, and when going from Fragment_C to Fragment_A there was the new instance on top of the old and at onBackPressed it popped the new instance, and showed me the old but how can I resolve so I won't need to press the back button? I tried to send a Boolean so if it's a new instance pop it, but it popped the old one I guess, because when I pressed back, it just quit the Activity instead of popping the new one.
Any help is appreciated!
An Activity-scoped ViewModel will make sharing data between child Fragments easier. Your Fragments observe the data in the ViewModel, so you don't even have to worry about passing data around. And with Navigation Component, you can use popUpTo and popUpToInclusive to pop Fragments B and C off the back stack, leaving just Fragment A.
If you're not familiar with these concepts, this free course covers them all wonderfully:
https://www.udacity.com/course/developing-android-apps-with-kotlin--ud9012