hello, Emmanouil!

how can I help you today?

hi Mark.

Need your knowledge about fragments

You see, I try to create a functionality, that I will be able to go forth and back between fragments. Obviously the backstack will not help, since I am aware that it just pops

use show()/hide() or attach()/detach()

(methods on FragmentTransaction)

So let's say I have fragment A->B->C-D, and I am on fragment V, If I want to go forth and fragment C is already created, to be able to re-open it and resume it from the old state

Apologies, ment I am on Fragment B*

whew, I was getting worried there :-)

have your Activity hold onto four Fragment objects in fields, for A, B, C, D

I have already tried the show/hide but unfortunately, the fragments are not populated the way I wish, they dont have the same state

yes

the state should not be affected by show()/hide()

all that is happening is that the views are marked as GONE, as far as I know

I see.

attach()/detach() will remove the views from the hierarchy, but Android holds onto the fragment's saved instance state Bundle

attach()/detach() therefore save more heap space, but attach() takes a bit more execution time, as onCreateView() should get called again

I have also tried to call the fragments by the TAG (in case they are already created of course), but for some reason there are a few that they will not open with the old state. Do you think I am doing something wrong there?

I have no good way of answering that

you might add more logging to determine what is going on

I see, was just looking for alternatives, but I will try the show and hide again as you suggested, perhaps I did something silly

IOW, are you somehow overwriting the state? or are you winding up with new fragment instances when you are not expecting?

the second.

findFragmentByTag() will not create a new instance, assuming that's what you mean by "call the fragments by the TAG"

Android creates new fragment instances on a configuration change

yeah I am using the findFragmentByTag

otherwise, you're the one who creates the fragment instances, as part of your FragmentTransactions

so, if you are getting new fragment instances, and you have not undergone a configuration change, the new instance should have come from your code

you might create a do-nothing zero-argument public constructor, where you can put a breakpoint or logging or something

to try to see who is creating instances and when

Do you have any Github sample I could use in your repo?

sample of what, specifically?

fragment navigation

um, I have a bit in the large-screen chapter

Good stuff

that would be the LargeScreen/ directory in the repo

Thanks a lot

otherwise, I do not do much with fragment navigation in the book, sorry

no probs

Thank you for the advice. Have a good day. It was helpful.

you're welcome!