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Android: Duplicating fragments in FragmentManager

EDIT: I want to solve problem of duplicating fragment in view Pager, removing them isn't the best solution.
I have a problem with FragmentManager in my app. Every time when I click "Wykłady teoretyczne" or "Wykłady popularnonaukowe" on Navigation Drawer my app is creating new fragment ScheduleFragment() which contains ViewPager and in SchedulePagerAdapter app is creating new 3 fragments (ScheduleEventFragment()) to swipe them in ScheduleFragment. My problem is that FragmentManager doesn't remove old ScheduleEventFragments, for all the time it keeps them in memory. How can I fix this problem?
I have my project on GitHub, please check it.
There you have screen from debuging

FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.remove(R.id.container,fragment,optionalTag);
fragmentTransaction.commit();You can also detach or replace

Always check if fragmemt.isAdded() and then only add the fragment if not.

Android UI Problems

I have a strange behaviour with the Android UI. At the beginning all works fine but after a minute the fragment always gets blank when replacing it with the FragmentManager. When reopening the app all looks fine again. I am using an AppCompatActivity does someone know a solution for this?
This is my replace code
var fragmentTransaction = FragmentManager.BeginTransaction();
fragmentTransaction.Replace(Resource.Id.frameLayout1, nextFrag).AddToBackStack("div_overview").Commit();
Edit:
I open the first fragment by using the following code in the MainActivity :
SupportFragmentManager.BeginTransaction().Replace(Resource.I‌​d.frameLayout1, fragments[1]).Commit();
This Fragment can open other fragments by button click. For this i am using
var fragmentTransaction = FragmentManager.BeginTransaction(); fragmentTransaction.Replace(Resource.Id.frameLayout1, nextFrag).AddToBackStack("div_overview").Commit();
This behaviour only happens after some time (mostly after the screen has been darken). The first transactions are working without any problems...
Thank you in advance!

FragmentTransaction replace method doesn't work properly

I have a bug with replacing fragments inside FrameLayout container.
When app is started first time everything is Ok but when I hide app and then resume it fragments start overlap each other when FragmentTransaction.replace method is called
I've seen almost all stackoverflow questions about such issues but I can't resolve this issue
Code:
<FrameLayout
android:id="#+id/frame"
android:layout_width="match_parent"
android:layout_height="match_parent">
</FrameLayout>
Add initial fragment:
getSupportFragmentManager().beginTransaction()
.add(R.id.frame, RequestFragment.newInstance(), REQUEST_FRAGMENT_TAG)
.commit();
Replace:
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
switch (menuItem.getItemId()) {
case R.id.request:
ft.replace(R.id.frame, RequestFragment.newInstance(), REQUEST_FRAGMENT_TAG);
ft.commit();
return true;
case R.id.finished:
ft.replace(R.id.frame, FinishedFragment.newInstance(), FINISHED_FRAGMENT_TAG);
ft.commit();
return true;
case R.id.questions:
ft.replace(R.id.frame, QuestionsFragment.newInstance(), QUESTIONS_FRAGMENT_TAG);
ft.commit();
return true;
default:
return true;
}

Difficult to say as your code provides no context as to when it is run but I suspect the issue is when you are adding your initial fragment.
You are calling add instead of replace which will just add the new fragment on top of any existing ones. It is perfectly fine to use replace even if the container does not yet contain anything.
Fragments survive in the FragmentManager and are automatically re-attached to their container when the Activity restarts. The correct procedure is to check for an existing Fragment before adding a new one.
Add initial fragment
Fragment f=getSupportFragmentManager().findFragmentById(R.id.frame);
if (f==null) {
getSupportFragmentManager().beginTransaction()
.replace(R.id.frame, RequestFragment.newInstance(), REQUEST_FRAGMENT_TAG).commit();
}
Also, it is helpful to make use of logging getSupportFragmentManager().getFragments().size(); whilst you are debugging. It lets you know how many fragments are currently in the FragmentManager and can highlight potential issues in your code. For example, if your count goes up every time you rotate the device, you are adding fragments and not checking for existing ones.

try to use FragmentTransaction.commitAllowingStateLoss() instead of using commit()

This sometimes happens because of the fragment background. Try setting solid background to all fragments in the stack so it's not empty or set to #null.

I wasn't calling the commit method at the end.

how can i back from one fragment to another fragment in android?

I am used to developed my applications fragments I have one problem
I am replacing fragments like
A -->B --> C --> D -->E -->F
How can i return back like
A <--B <-- C <-- D <--E <--F
I am using code like
getActivity().getFragmentManager().popBackStack();
this worked fine but some times closed app without cross
is there any solution i dnot how to slove the problem due have any idea please guide me
Advance thanks all``

With no code available I just post what it's working for me:
when switching from a Fragment to another i use this (if you aren't using the support libraries you have to remove the 'Support' prefix):
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction transaction = fm.beginTransaction();
transaction.replace(R.id.fragmentContainer,
MyFragment.newInstance());
transaction.addToBackStack(null);
transaction.commit();
The addToBackStack adds the fragment to the backstack... so when you press back button the previous fragment will pop up.
Hope it helps.

Transaction of fragments in android results in blank screen

If it helps, what I want is similar to what is done in this google tutorial
But there a fragment is created prior to the transition. If I do that the transition works fine; but I can't use this approach
=====
Aiming to API 7+ I am just trying to have one Fragment visible in the whole screen and using a button (a drawn button, with an onTouch event) then alternate to a second fragment and viceversa.
But I either get a blank screen when I replace the first fragment with the second, or if I use fragmentTransaction.show and fragmentTransaction.hide; I can switch two times before I get blank screen. I dont want to have on backstack.
I am creating the fragments in MainActivity's onCreate:
DiceTable diceTable = new DiceTable();
Logger logger = new Logger();
fragmentTransaction.add(diceTable, DICETABLE_TAG);
fragmentTransaction.add(logger, LOGGER_TAG);
fragmentTransaction.add(R.id.fragment_container, logger);
fragmentTransaction.add(R.id.fragment_container, diceTable);
Then on one method (called from the fragments) I do the switch:
Logger logger = (Logger)fragmentManager.findFragmentByTag(LOGGER_TAG);
DiceTable diceTable = (DiceTable)fragmentManager.findFragmentByTag(DICETABLE_TAG);
if (diceTable.isVisible()) {
fragmentTransaction.replace(R.id.fragment_container, logger);
fragmentTransaction.commit();
fragmentTransaction.hide(diceTable);
fragmentTransaction.show(logger);
}
else if (logger.isVisible()) {
fragmentTransaction.replace(R.id.fragment_container, diceTable);
fragmentTransaction.commit();
fragmentTransaction.hide(logger);
fragmentTransaction.show(diceTable);
}
This is not how I should do this?
Blank screen when replacing fragments

Try to initialize fragments in that way:
private void initFragments() {
mDiceTable = new DiceTable();
mLogger = new Logger();
isDiceTableVisible = true;
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.add(R.id.fragment_container, mDiceTable);
ft.add(R.id.fragment_container, mLogger);
ft.hide(mLogger);
ft.commit();
}
And then flip between them in that way:
private void flipFragments() {
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
if (isDiceTableVisible) {
ft.hide(mDiceTable);
ft.show(mLogger);
} else {
ft.hide(mLogger);
ft.show(mDiceTable);
}
ft.commit();
isDiceTableVisible = !isDiceTableVisible;
}

You are combining two different methods of changing which Fragment is shown:
Calling replace() to replace the contents of the container with a different Fragment
Calling hide() to remove a Fragment, then calling show() to show another Fragment.
Pick one method and stick with it. The Building a Flexible UI guide uses just the replace() method, so I would start by trying to remove all of your calls to show() and hide().
Also see Android Fragments: When to use hide/show or add/remove/replace? for a quick summary of when it might be beneficial to use hide/show instead of replace.

In case anyone has tried all of the already suggested answers and is still facing the issue, like I was a few moments ago, the problem may come from a different source than your fragments.
In my case, I was switching between fragments correctly, but the reason for the blank screen was that in each new fragment I was trying to asynchronously load images by starting a new Thread every time (something a bit like this) instead of the recommended AsyncTask, or better yet the newSingleThreadExecutor, since AsyncTask is deprecated.
I disturbed the background enough that the fragment was just not showing up unless I navigated to a different app then back.
So unless your mistake is similar to mine my suggestion might be kind of vague but try to see if anything is happening in your fragment that may be intensive on the resources (commenting out different pieces of code may help in investigating this).