Develop Reference

Android: how to create a custom back button for fragments in a KIOSK app

I CANT use ActionToolbar because this is a KIOSK app with a custom header fragment that needs to be displayed at all time. Hence my situation, I have a basic ImageButton on the said header fragment, and I want to implement the functionality of a basic ActionToolbar.
I add my fragment to the main container like this:
getSupportFragmentManager().beginTransaction()
.replace(R.id.main_container, UserListFragment.newInstance())
.addToBackStack("foo")
.commit();
The question is, how do I restore the state of my main_container before the current fragment was replaced with UserListFragment.
Like : fragment A is showing, replacing fragment A with B, pressing some button in my header fragment to pop the fragment B so again fragment A is showing.

You should consider switching to Android Jetpack Navigation Component it was created for your type of situation.
Check: https://stackoverflow.com/a/62252603/8714139
Cheers!

How do I retain the state of my ViewPager in my TabLayout when I'm replacing a Fragment on top of it?

I have a single activity that uses a bunch of different Fragments. I have a TabContainer Fragment that holds a TabLayout which uses a ViewPager to handle tab navigation. Each Tab is its own Fragment.
In one of my tabs, I want to tap and place a fragment on top of my Tabbed fragment. This is meant to be a "details" sort of screen, so I don't want the tabs to be visible. I'm using this and it works as intended:
fragmentTransaction.replace(android.R.id.content, fragmentToDisplay).addToBackStack(null).commit();
Now, when I navigate back, the content in my tab is empty. The content in the tab directly next to that tab is also empty. When I navigate two tabs away, the content is recreated and the normal functionality returns. Why is content not being recreated on the tabs initially when I remove my "detail" fragment?

It turns out that I was simply not passing the correct FragmentManager to the FragmentStatePagerAdapter.
I needed to call getChildFragmentManager() on the Fragment, not getSupportFragmentManager() on the activity.
Thanks to these two posts for the answer:
Fragment in ViewPager not restored after popBackStack
and: Replacing ViewPager with Fragment - Then Navigating Back

Android - how to slide screens, inside a fragment

I've created an app, that has a main activity with a drawer menu so the user can click on some option and a fragment is open inside the activity.
What I'd like to do is to have several screens in one of the options and to navigate between them by tabs/slide the screen.
I saw an example of doing it inside one activity and with a fragment per 'sub-screen', my question is: how can I do it when I'm already 'inside' a fragment?
Thanks

Fragments can support having other Fragments inside them. The key to making this work is to remember to use getChildFragmentManager() to get the Fragment's FragmentManager instead of getFragmentManager() which gets the Activity's FragmentManager.
If you want to swipe between views, use a ViewPager inside your Fragment UI. The ViewPager will use a FragmentPagerAdapter to handle the Fragments for display.

Viewpager inside fragment and back button

I asked this question before getChildFragmentManager() and viewpager without any responses, probably because the explanation was too long.
Simply put I have a viewpager inside a fragment. The pages inside that viewpager need to be replaced through a series of screens. Pressing back on those screens will not exit the application. How do I do this?
challenges:
viewpager xml does not use framelayout. when I use the replace method, what container
id do I use?
when replacing the fragments why would I use getChildFragmentManager each time if that is private to the current fragment?
#goonedroid: that's not the case I'm looking for here. The only similarity is that the fragment has a viewpager. My viewpager's pages need to be replaced when clicked:
I have a navdrawer. Clicking item 2 shows FragmentA. Clicking FragmentA replaces it with FragmentB. Clicking FragmentB replaces it with FragmentC. Clicking FragmentC takes you back to FragmentB. Fragments are added to the backstack for proper back navigation.
Clicking item 1 in the navdrawer shows FragmentZ with a viewpager. The viewpagers pages are just FragmentA and all the aforementioned behavior. But going from A to B here, then pressing back shows no pages in the viewpager.

I finally figured out a solution, not sure why this works because I thought an Activity's getSupportFragmentManager() returns the same fragment manager as its fragment's getFragmentManager().
Anyway, instead of getFragmentManager() in the fragments, use getActivity().getFragmentManager()

FragmentPagerAdapter inside Fragment

I'm having a bit of trouble implementing a design based around multiple ViewPagers.
At a high level, I have a FragmentActivity with just a FrameLayout as it's content. I have 3 different Fragments that I want to display. All 3 are full screen and only 1 will be used at a time.
Fragment 1 is a basic fragment with some TextViews and ImageViews.
Fragment 2 has a ViewPager and a FragmentPagerAdapter that feeds it several simple fragments.
Fragment 3 has a ViewPager and a FragmentPagerAdapter that feeds it several simple fragments (that are different from Fragment 2)
In my FragmentActivity onCreate() I get the FragmentManager and begin a transaction to replace whatever is in my FrameLayout with a new instance of Fragment 2.
At this point everything is working as expected. My ViewPager in Fragment 2 works perfectly.
Now I have a menu option that replaces the Fragment 2 in my FrameLayout with a new instance of Fragment 3. This also works fine.
The problem arises when I try to put Fragment 2 back into the FrameLayout with another replace transaction. I see my PagerIndicater at the top, but my pages are blank.
I've tried just creating a new instance of my Fragment 2 and calling a replace transaction. I've also tried setting a tag on my Fragments when I call replace and adding a findFragmentByTag check before my replace instead of creating a new instance. Both gave me the same result of blank pages after my second replace.
For reference
My first design was simply a FragmentActivity with a ViewPager and a ViewIndicater. I only had Fragment 2 and Fragment 3 from my description above and a menu option to switch between them. To switch I had 2 different FragmentPagerAdapters defined and just called ViewPager.setAdapter to set the selected FragmentPagerAdapter. This was working perfectly, but now I need a new top level Fragment that isn't using ViewPager at all. This is why I decided to move my ViewPagers out into their own Fragments. My idea being that I would just swap in my fragments to a FrameLayout.
I don't have my code in front of me right now so I can't post any, but I'll add some code to my question tomorrow to help facilitate answers.

This question is a possible duplicate of Navigating back to FragmentPagerAdapter -> fragments are empty.
If your app can handle it (API 17), use getChildFragmentManager(). This problem seems to occur when using a Fragment to host your ViewPager and using FragmentPagerAdapter. Changing to FragmentStatePagerAdapter seemed to fix the problem as well, but I still think using getChildFragmentManager() is the smartest thing to do.

brockoli you can used not "good way". But for my it's worked.
You can use in view 2 layouts, where you bind fragments. First - for fragment with fragments. Second - for other fragments.
On replace fragment with fragments do not replace, but only change visibility first layout to gone and add new fragment to second layout. On back, remove fragment from second layout and set visibility for first layout to visible.