Develop Reference

Android Back to previous fragment by popBackStack

I have 3 fragments: Home, A and B. Home and A are in mobile navigation menu.
User goes from A to B and then press back button. The issue that if I use getFragmentManager().popBackStack(); onCreateView of fragment A is calling and I have duplicating of content.
But if I use getActivity().onBackPressed(); it goes to Home fragment instead of A.
How to display fragment A by clicking back button without refreshing the view?
Here is how I make transaction from A to B
CertificateItemFragment certificateItemFragment = new CertificateItemFragment(item);
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.nav_host_fragment, certificateItemFragment).addToBackStack(null);
fragmentTransaction.commit();

You need to know some premise before using FragmentManager.
in Activity there is FragmentManager and we should call it with getSupportFragmentManager(), getFragmentManager() is deprecated.
in Fragment there are multiple FragmentManagers called ParentFragmentManager and ChildFragmentManager, the final FragmentManager which is deprecated too. And ParentFragmentManager will be same as Activity's FragmentManager
getActivity().onBackPressed() will pull out fragment if any stack exists in Activity's FragmentManager
fragmentManager.popBackStack() will pull out fragment if any stack exists in Activity's or Fragment's FragmentManager rely on who calls
Base on above points
(1) If You want to hold fragments in Activity, you should call getSupportFragmentManager() in Activity, and call getParentManager() in Fragment, then onBackPressed() will pull out the fragment you last add to stack.
(2) If you want to hold fragments in a Fragment and Separated from Activity, you should call getChildFragmentManager() in Fragment, then activity.onBackPressed() will pull out the fragment which in Activity's fragment stack and ignore other fragments in Fragment's fragment stack.
For question will be same as case (1), and if you dont want re-create fragment, you should use add() instead of replace()
in Fragment A
CertificateItemFragment certificateItemFragment = new CertificateItemFragment(item);
FragmentManager fragmentManager = getParentFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.add(R.id.nav_host_fragment, certificateItemFragment).addToBackStack(CertificateItemFragment.TAG);
fragmentTransaction.commit();
now onBackPressed() will backstack from CertificateItemFragment to Pre-Fragment

In normal case navigation item list menu open fragment which are replace to each other but when we move inside of any item as like in your case move from fragment A to B,
In this case normally we use another activity on which create fragment.
If you do't want to use activity then, you just need to add fragment.
try below code that may help you
CertificateItemFragment certificateItemFragment = new CertificateItemFragment(item);
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.add(R.id.nav_host_fragment, certificateItemFragment).addToBackStack(CertificateItemFragment.TAG);
fragmentTransaction.commit();

How to replace fragment that is loaded by navigationView

I have a navigation view that loads some fragments depending on which is pressed. In one of the fragments, I want to have a button, which when it is pressed, the fragment changes from the one loaded by the navigation view to a different fragment. I have tried using
ProfileEditFragment pef = new ProfileEditFragment();
FragmentManager fm = getSupportFragmentManager();
fm.beginTransaction().remove(pef).replace(R.id.drawer_layout, pef, "Fragment")
.addToBackStack(null).commit();
When I do this, it loads the other fragment on top of the current fragment, rather than replace it, even though I used the replace function. How do I fix this?

Can you try this:
ProfileEditFragment pef = new ProfileEditFragment();
FragmentTransaction transaction =getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.drawer_layout, pef);
transaction.addToBackStack(null);
// Commit the transaction
transaction.commit();

Added fragment scrolled down

I have two fragments the first fragment contains list of linear layouts and the whole fragment is in scroll view the second fragment is added and the first is hidden on choosing item from the first.
The problem is the second fragment is created scrolled down if the first fragment was scrolled down.
I tried the ways to force second fragment to be scrolled to (0,0) but failed.
the code used to add the second fragment
public void setActionOnClick(String id) {
CommentFragment frag = new CommentFragment();
Bundle bundle = new Bundle();
bundle.putString("id", id);
bundle.putString("TAG", TAG_NEWS_STORY);
((MainActivity) getActivity()).setCurrentTag(TAG_NEWS_STORY);
frag.setArguments(bundle);
android.support.v4.app.FragmentTransaction fragmentTransaction =
getActivity().getSupportFragmentManager().beginTransaction();
fragmentTransaction.setCustomAnimations(android.R.anim.fade_in,
android.R.anim.fade_out);
fragmentTransaction.add(R.id.main_content, frag, TAG_NEWS_STORY);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
}
on Attach of second fragment the first fragment is hidden.
I don't want to use fragmentTransaction.replace because there are calls to the api which I don't want to reload.

this is an old question but. probably your fragment place_hoder is inside an scrollview.
just check if R.id.main_content is in a scrollview or not.
you should add the ScrollView to the fragment-layout instead of instantiating the fragment inside one

Before this:
android.support.v4.app.FragmentTransaction fragmentTransaction =
getActivity().getSupportFragmentManager().beginTransaction();
Add code to remove old fragment:
getSupportFragmentManager().beginTransaction().remove(yourOldFragment).commitAllowingStateLoss();

how to add two fragments in one activity

Android: I have a list Fragment on an activity.based on the choice, another fragment will be shown on the same activity
but the other fragment should be replaced and i don't know how to do that when the list fragment is fixed !

From google guide for replacing fragments : http://developer.android.com/training/basics/fragments/fragment-ui.html
// Create fragment and give it an argument specifying the article it should show
ArticleFragment newFragment = new ArticleFragment();
Bundle args = new Bundle();
args.putInt(ArticleFragment.ARG_POSITION, position);
newFragment.setArguments(args);
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack so the user can navigate back
transaction.replace(R.id.fragment_container, newFragment);
transaction.addToBackStack(null);
// Commit the transaction
transaction.commit();

There's a guide on Fragments in the developers portal. Take a look at the "programmatically add" part (and at the whole guide actually). In short: you need a ViewGroup that is used as a container for the fragments and a FragmentTransaction that is used to add/replace fragment in this container.
Something like (taken from the guide):
FragmentManager fragmentManager = getFragmentManager()
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
ExampleFragment fragment = new ExampleFragment();
fragmentTransaction.add(R.id.fragment_container, fragment);//fragment_container is the ID of the ViewGroup container in your layout
fragmentTransaction.commit();
in your activity.
EDIT:
Long story short - don't put a fixed fragment in your activity's layout. Instead place a container, dynamically add your first fragment in the container and replace it with another fragment when you need to do so (by using FragmentTransaction's replace).

Reset/reload fragment container

How can I reset or reload a fragment container, to make it empty.
I have a master detail view and I want to reset the detail container to empty on a menu item click.This works in some cases and does not in some.
NullFragment fragment = new NullFragment();
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager
.beginTransaction();
fragmentTransaction.replace(R.id.item_detail_container,
fragment);
int count = fragmentManager.getBackStackEntryCount();
fragmentManager.popBackStackImmediate(count, 0);
fragmentTransaction.commit();

Usually you simply remove the fragment from it.
For example do something like
getFragmentManager().beginTransaction().remove(getFragmentManager().findFragmentById(R.id.your_container)).commit();
this will remove the fragment from the your_container holding it.
This gets the fragment currently present in your_container
getFragmentManager().findFragmentById(R.id.your_container)
and this remove the fragment
getFragmentManager().beginTransaction().remove(fragment).commit();
EDIT
Also sometimes it is useful to ensure all transactions are performed and finished, this can be done by using
getFragmentManager().executePendingTransactions();