Develop Reference

Conditional Navigation in Android Navigation Component

I have 3 fragments A, B and C with A being the start destination of my nav graph. When the user starts the app, I check in fragment A if there are previously stored results. If there are, I want to navigate straight to fragment C. I have managed to get this to work. However, when the user presses back in fragment C in this case, I want them to be taken to fragment B instead of A, and that's what I need help figuring out.
Note: Fragment A is just a setup fragment which is only visited once when the app starts. Which means when the user presses back from fragment B, they are taken to OS home screen.

You can override onBackPress() and replace whatever fragment you are in with FragmentB like this
#Override
public void onBackPressed() {
int stackCount = getFragmentManager().getBackStackEntryCount();
if (stackCount == 1) {
super.onBackPressed(); // if you don't have any fragments in your backstack yet.
} else {
// just replace container with fragment as you normally do;
FragmentManager fm = getFragmentManager();
fm.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);//clear backstackfirst and then you can exit the app onbackpressed from home fr
FragmentTransaction transaction = fm.beginTransaction();
transaction.replace(R.id.container, new FragmentB());
transaction.commit();
}
}
This is the original answer ,you can take a look answer by Rainmaker

You can override your onBackPressed on fragment C and call your navController to go back to fragment b creating a new action from C to B
navController.navigate(R.id.action_CFragment_to_BFragment)

fragment transaction - pop backstack and then add fragment

I am trying to do the following use case in Android Fragments. I have 2 fragments.
Fragment A -> Fragment B
When a user does something in Fragment B, I want to have the back stack as follows
Fragment A -> Fragment C. So, when the user presses back I want the user to go back to Fragment A.
I have tried the following
mFragmentManager.popBackStackImmediate();
FragmentTransaction fragmentTransaction = fMgr.beginTransaction()
.replace(R.id.base, Fragment_C, "1")
.addToBackStack(null)
.commitAllowingStateLoss();
The problem here is that I can see Fragment A for a short period of time before Fragment C is shown
If I do the following
mFragmentManager.popBackStackImmediate();
FragmentTransaction fragmentTransaction = fMgr.beginTransaction()
.replace(R.id.base, Fragment_C, "1")
.addToBackStack(null)
.commitNowAllowingStateLoss();
I get the error
This transaction is already being added to the back stack
I can get Fragment C to show up if I do this BUT
mFragmentManager.popBackStackImmediate();
FragmentTransaction fragmentTransaction = fMgr.beginTransaction()
.replace(R.id.base, Fragment_C, "1")
.commitNowAllowingStateLoss();
This works and I don't see Fragment A and see Fragment C but the back button takes the user out of the application. So, is it possible that we can pop the back stack of the fragment and then add another fragment to the back stack w/o showing Fragment A AND the back button takes the user back to Fragment A

Here is an easy method to add fragments to fragments or to adapters within fragments...
from your base activity, make your fragment manager static. assume this activity is called dashboard.
static FragmentManager support;
Don't forget to initialize this in onCreate.
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layout_dashboard);
support = getSupportFragmentManager();
define your new fragment inside your adapter or fragment.
users_item_fragment dialog = new users_item_fragment();
//also, let's add some data...
Bundle args = new Bundle();
args.putString("device", devicesList.get(position));
use the following method to add the fragment easily wherever you would like
//pick an easily remembered tag
public void replace(Fragment fragment, String tag){
FragmentManager man = dashboard.support;
FragmentTransaction fragt = man.beginTransaction();
if(!fragment.isAdded()) {
dashboard.lastTag = dashboard.fragtag;//not needed, but helpful w/ backpresses
fragt.add(R.id.fragment_container, fragment, tag)
.hide(man.findFragmentByTag(fragtag)).commit();
dashboard.fragtag = dashboard.tag;//not needed, but helpful w/ backpresses
}
if(fragment.isAdded() && fragment.isHidden()) {
dashboard.lastTag = dashboard.fragtag;//not needed, but helpful w/ backpresses
fragt.show(fragment);
fragt.hide(man.findFragmentByTag(fragtag)).commit();
dashboard.fragtag = dashboard.tag;//not needed, but helpful w/ backpresses
}
}
To implement this with backpresses working correctly, add this in you onBackPress method of your main activity:
#Override
public void onBackPressed() {
FragmentManager man = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = man.beginTransaction();
fragmentTransaction.hide(getSupportFragmentManager().findFragmentByTag(fragtag))
.show(getSupportFragmentManager().findFragmentByTag(lastTag)).commit();
fragtag = lastTag;// holds the last fragment
}
}
It's easy to see the logic here and easy to manipulate back press events using this.

Returning to specific fragment from activity

I am developing an application which is based on Fragment and main activity implements the Slide navigation. I have got three fragment."A", "B", "C" Let say I traverse from "B" fragment to an independent activity. When I try to return from Activity, it lands me up on "A" Fragment where as I want to return to same fragment from where I traversed to activity.
I am using the below code to transact with Fragments
if (fragment != null) {
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.container_body, fragment);
fragmentTransaction.commit();
}
How to do this?

check it out my below code,
#Override
public void onBackPressed() {
super.onBackPressed();
FragmentManager fm = getSupportFragmentManager();
if (fm.getBackStackEntryCount() == 1) {
//your code goes here
} else if (fm.getBackStackEntryCount() > 1) {
fm.popBackStack();
//your code goes here
} else {
fm.popBackStack();
//your code goes here
}
}
count return number of fragment you have crossed, comment it if you need any help

The problem you're dealing with pretty common in Android and they've explained in a good article in the docs.
So basically, you want to use the BackStack but for your specific issue, there is another solution: when you're moving to the other activity, the original one (which contains B) is basically not destroyed so, what you could do is put states in this activity (the one containing A, B and C) and, as soon as, you come back from your independant activity, your onResume will be fired and you just have to override it to make it display the fragment you want.

Fragments and backstage sometimes get messed up

I have an activity with a container for fragments and a NavigationDrawer. If I select an item in the drawer, I call updatePage(index).
I also call updatePage(0) if I create the activity and the savedInstanceState == null to init my activity.
One fragment has a sub fragment and therefor it just replaces itself by the subfragment and adds the subfragment to the backstack, so that the user can navigate back to the previous fragment. In this fragment I call following code directly:
#Override
public void onClick(View view)
{
Event event = (Event)view.getTag();
FragmentManager fm = getActivity().getSupportFragmentManager();
GamesFragment f = new GamesFragment();
Bundle bundle = new Bundle();
bundle.putParcelable(GamesFragment.KEY_EVENT, event);
f.setArguments(bundle);
FragmentTransaction ft = fm.beginTransaction()
.replace(R.id.frame_container, f, f.getClass().getName())
.addToBackStack(null);
ft.commit();
}
Why does sometimes the removing of the old fragment not work? I get overlaying fragments, but only sometimes.
My activities updatePage function looks like following:
private void updatePage(int drawerSelection)
{
mDrawer.closeDrawer();
Fragment f = null;
FragmentManager fm = getSupportFragmentManager();
switch (drawerSelection)
{
case 0:
f = fm.findFragmentByTag(HomeFragment.class.getName());
if (f == null)
f = new HomeFragment();
break;
case 1:
f = fm.findFragmentByTag(EventFragment.class.getName());
if (f == null)
f = new EventFragment();
break;
default:
break;
}
if (f != null && !f.isAdded())
{
// SOLUTION:
// Backstack clearen
// fm.popBackStackImmediate(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
FragmentTransaction ft = fm.beginTransaction();
ft.replace(R.id.frame_container, f, f.getClass().getName());
ft.commit();
}
}

I saw such situation few times and I bet that it can happen after replacing with addToBackStack. Easiest fix is to add background to fragment layout. From android doc:
Note: When you remove or replace a fragment and add the transaction to the back stack, the fragment that is removed is stopped (not destroyed). If the user navigates back to restore the fragment, it restarts. If you do not add the transaction to the back stack, then the fragment is destroyed when removed or replaced.
This view is not redrawed entirely just overdrawed and if second fragment doesn't has background or view container redraw you will get effect as described. That's my theory :>. Sometimes Android documentation is not as clear as we would like it to be.

The problem is following use case:
Going to the EventFragment from the GameFragment pushes the "remove(EventFragment).add(GameFragment)" transaction to the backstack. If I now press the back button, this transaction will be undone and everything is fine. The backstack is empty again and everything works. BUT, if I don't press the back button, but change to another fragment through the menu, the backstack does still have the above mentioned transaction. Pressing back will now try to undo this transaction... It will just readd the EventFragment before the code in my menu click handler adds the fragment from the menu... This is how it could happen...
Easy solution, if I only want one backstack for every menu entry and want to delete the backstack, if I select another area of my app in the menu is, to clear the backstack before I go to another area through the menu...
So adding ' fm.popBackStackImmediate(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);' before replacing the the current fragment will solve the problem (I added this solution as a comment to my main post)

Problems with Android Fragment back stack

I've got a massive problem with the way the android fragment backstack seems to work and would be most grateful for any help that is offered.
Imagine you have 3 Fragments
[1] [2] [3]
I want the user to be able to navigate [1] > [2] > [3] but on the way back (pressing back button) [3] > [1].
As I would have imagined this would be accomplished by not calling addToBackStack(..) when creating the transaction that brings fragment [2] into the fragment holder defined in XML.
The reality of this seems as though that if I dont want [2] to appear again when user presses back button on [3], I must not call addToBackStack in the transaction that shows fragment [3]. This seems completely counter-intuitive (perhaps coming from the iOS world).
Anyway if i do it this way, when I go from [1] > [2] and press back I arrive back at [1] as expected.
If I go [1] > [2] > [3] and then press back I jump back to [1] (as expected).
Now the strange behavior happens when I try and jump to [2] again from [1]. First of all [3] is briefly displayed before [2] comes into view. If I press back at this point [3] is displayed, and if I press back once again the app exits.
Can anyone help me to understand whats going on here?
And here is the layout xml file for my main activity:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<fragment
android:id="#+id/headerFragment"
android:layout_width="match_parent"
android:layout_height="wrap_content"
class="com.fragment_test.FragmentControls" >
<!-- Preview: layout=#layout/details -->
</fragment>
<FrameLayout
android:id="#+id/detailFragment"
android:layout_width="match_parent"
android:layout_height="fill_parent"
/>
Update
This is the code I'm using to build by nav heirarchy
Fragment frag;
FragmentTransaction transaction;
//Create The first fragment [1], add it to the view, BUT Dont add the transaction to the backstack
frag = new Fragment1();
transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.detailFragment, frag);
transaction.commit();
//Create the second [2] fragment, add it to the view and add the transaction that replaces the first fragment to the backstack
frag = new Fragment2();
transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.detailFragment, frag);
transaction.addToBackStack(null);
transaction.commit();
//Create third fragment, Dont add this transaction to the backstack, because we dont want to go back to [2]
frag = new Fragment3();
transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.detailFragment, frag);
transaction.commit();
//END OF SETUP CODE-------------------------
//NOW:
//Press back once and then issue the following code:
frag = new Fragment2();
transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.detailFragment, frag);
transaction.addToBackStack(null);
transaction.commit();
//Now press back again and you end up at fragment [3] not [1]
Many thanks

Explanation: on what's going on here?
If we keep in mind that .replace() is equal with .remove().add() that we know by the documentation:
Replace an existing fragment that was added to a container. This is essentially the same as calling remove(Fragment) for all currently added fragments that were added with the same containerViewId and then add(int, Fragment, String) with the same arguments given here.
then what's happening is like this (I'm adding numbers to the frag to make it more clear):
// transaction.replace(R.id.detailFragment, frag1);
Transaction.remove(null).add(frag1) // frag1 on view
// transaction.replace(R.id.detailFragment, frag2).addToBackStack(null);
Transaction.remove(frag1).add(frag2).addToBackStack(null) // frag2 on view
// transaction.replace(R.id.detailFragment, frag3);
Transaction.remove(frag2).add(frag3) // frag3 on view
(here all misleading stuff starts to happen)
Remember that .addToBackStack() is saving only transaction not the fragment as itself! So now we have frag3 on the layout:
< press back button >
// System pops the back stack and find the following saved back entry to be reversed:
// [Transaction.remove(frag1).add(frag2)]
// so the system makes that transaction backward!!!
// tries to remove frag2 (is not there, so it ignores) and re-add(frag1)
// make notice that system doesn't realise that there's a frag3 and does nothing with it
// so it still there attached to view
Transaction.remove(null).add(frag1) //frag1, frag3 on view (OVERLAPPING)
// transaction.replace(R.id.detailFragment, frag2).addToBackStack(null);
Transaction.remove(frag3).add(frag2).addToBackStack(null) //frag2 on view
< press back button >
// system makes saved transaction backward
Transaction.remove(frag2).add(frag3) //frag3 on view
< press back button >
// no more entries in BackStack
< app exits >
Possible solution
Consider implementing FragmentManager.BackStackChangedListener to watch for changes in the back stack and apply your logic in onBackStackChanged() methode:
Trace a count of transaction;
Check particular transaction by name FragmentTransaction.addToBackStack(String name);
Etc.

It seems as though fragment [3] is not removed from the view when back is pressed so you have to do it manually!
First of all, don't use replace() but instead use remove and add separately. It seems as though replace() doesn't work properly.
The next part to this is overriding the onKeyDown method and remove the current fragment every time the back button is pressed.
#Override
public boolean onKeyDown(int keyCode, KeyEvent event)
{
if (keyCode == KeyEvent.KEYCODE_BACK)
{
if (getSupportFragmentManager().getBackStackEntryCount() == 0)
{
this.finish();
return false;
}
else
{
getSupportFragmentManager().popBackStack();
removeCurrentFragment();
return false;
}
}
return super.onKeyDown(keyCode, event);
}
public void removeCurrentFragment()
{
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
Fragment currentFrag = getSupportFragmentManager().findFragmentById(R.id.detailFragment);
String fragName = "NONE";
if (currentFrag!=null)
fragName = currentFrag.getClass().getSimpleName();
if (currentFrag != null)
transaction.remove(currentFrag);
transaction.commit();
}

First of all thanks #Arvis for an eye opening explanation.
I prefer different solution to the accepted answer here for this problem. I don't like messing with overriding back behavior any more than absolutely necessary and when I've tried adding and removing fragments on my own without default back stack poping when back button is pressed I found my self in fragment hell :) If you .add f2 over f1 when you remove it f1 won't call any of callback methods like onResume, onStart etc. and that can be very unfortunate.
Anyhow this is how I do it:
Currently on display is only fragment f1.
f1 -> f2
Fragment2 f2 = new Fragment2();
this.getActivity().getSupportFragmentManager().beginTransaction().replace(R.id.main_content,f2).addToBackStack(null).commit();
nothing out of the ordinary here. Than in fragment f2 this code takes you to fragment f3.
f2 -> f3
Fragment3 f3 = new Fragment3();
getActivity().getSupportFragmentManager().popBackStack();
getActivity().getSupportFragmentManager().beginTransaction().replace(R.id.main_content, f3).addToBackStack(null).commit();
I'm not sure by reading docs if this should work, this poping transaction method is said to be asynchronous, and maybe a better way would be to call popBackStackImmediate(). But as far I can tell on my devices it's working flawlessly.
The said alternative would be:
final FragmentActivity activity = getActivity();
activity.getSupportFragmentManager().popBackStackImmediate();
activity.getSupportFragmentManager().beginTransaction().replace(R.id.main_content, f3).addToBackStack(null).commit();
Here there will actually be brief going back to f1 beofre moving on to f3, so a slight glitch there.
This is actually all you have to do, no need to override back stack behavior...

I know it's a old quetion but i got the same problem and fix it like this:
First, Add Fragment1 to BackStack with a name (e.g "Frag1"):
frag = new Fragment1();
transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.detailFragment, frag);
transaction.addToBackStack("Frag1");
transaction.commit();
And then, Whenever you want to go back to Fragment1 (even after adding 10 fragments above it), just call popBackStackImmediate with the name:
getSupportFragmentManager().popBackStackImmediate("Frag1", 0);
Hope it will help someone :)

After #Arvis reply i decided to dig even deeper and I've written a tech article about this here: http://www.andreabaccega.com/blog/2015/08/16/how-to-avoid-fragments-overlapping-due-to-backstack-nightmare-in-android/
For the lazy developers around. My solution consists in always adding the transactions to the backstack and perform an extra FragmentManager.popBackStackImmediate() when needed (automatically).
The code is very few lines of code and, in my example, I wanted to skip from C to A without jumping back to "B" if the user didn't went deeper in the backstack (ex from C navigates to D).
Hence the code attached would work as follow
A -> B -> C (back) -> A
&
A -> B -> C -> D (back) -> C (back) -> B (back) -> A
where
fm.beginTransaction().replace(R.id.content, new CFragment()).commit()
were issued from "B" to "C" as in the question.
Ok,Ok here is the code :)
public static void performNoBackStackTransaction(FragmentManager fragmentManager, String tag, Fragment fragment) {
final int newBackStackLength = fragmentManager.getBackStackEntryCount() +1;
fragmentManager.beginTransaction()
.replace(R.id.content, fragment, tag)
.addToBackStack(tag)
.commit();
fragmentManager.addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
#Override
public void onBackStackChanged() {
int nowCount = fragmentManager.getBackStackEntryCount();
if (newBackStackLength != nowCount) {
// we don't really care if going back or forward. we already performed the logic here.
fragmentManager.removeOnBackStackChangedListener(this);
if ( newBackStackLength > nowCount ) { // user pressed back
fragmentManager.popBackStackImmediate();
}
}
}
});
}

If you are Struggling with addToBackStack() & popBackStack() then simply use
FragmentTransaction ft =getSupportFragmentManager().beginTransaction();
ft.replace(R.id.content_frame, new HomeFragment(), "Home");
ft.commit();`
In your Activity In OnBackPressed() find out fargment by tag and then do your stuff
Fragment home = getSupportFragmentManager().findFragmentByTag("Home");
if (home instanceof HomeFragment && home.isVisible()) {
// do you stuff
}
For more Information https://github.com/DattaHujare/NavigationDrawer
I never use addToBackStack() for handling fragment.

I think, when I read your story that [3] is also on the backstack. This explains why you see it flashing up.
Solution would be to never set [3] on the stack.

I had a similar issue where I had 3 consecutive fragments in the same Activity [M1.F0]->[M1.F1]->[M1.F2] followed by a call to a new Activity[M2]. If the user pressed a button in [M2] I wanted to return to [M1,F1] instead of [M1,F2] which is what back press behavior already did.
In order to accomplish this I remove [M1,F2], call show on [M1,F1], commit the transaction, and then add [M1,F2] back by calling it with hide. This removed the extra back press that would have otherwise been left behind.
// Remove [M1.F2] to avoid having an extra entry on back press when returning from M2
final FragmentTransaction ftA = fm.beginTransaction();
ftA.remove(M1F2Fragment);
ftA.show(M1F1Fragment);
ftA.commit();
final FragmentTransaction ftB = fm.beginTransaction();
ftB.hide(M1F2Fragment);
ftB.commit();
Hi
After doing this code: I'm not able to see value of Fragment2 on pressing Back Key.
My Code:
FragmentTransaction ft = fm.beginTransaction();
ft.add(R.id.frame, f1);
ft.remove(f1);
ft.add(R.id.frame, f2);
ft.addToBackStack(null);
ft.remove(f2);
ft.add(R.id.frame, f3);
ft.commit();
#Override
public boolean onKeyDown(int keyCode, KeyEvent event){
if(keyCode == KeyEvent.KEYCODE_BACK){
Fragment currentFrag = getFragmentManager().findFragmentById(R.id.frame);
FragmentTransaction transaction = getFragmentManager().beginTransaction();
if(currentFrag != null){
String name = currentFrag.getClass().getName();
}
if(getFragmentManager().getBackStackEntryCount() == 0){
}
else{
getFragmentManager().popBackStack();
removeCurrentFragment();
}
}
return super.onKeyDown(keyCode, event);
}
public void removeCurrentFragment()
{
FragmentTransaction transaction = getFragmentManager().beginTransaction();
Fragment currentFrag = getFragmentManager().findFragmentById(R.id.frame);
if(currentFrag != null){
transaction.remove(currentFrag);
}
transaction.commit();
}

executePendingTransactions() , commitNow() not worked (
Worked in androidx (jetpack).
private final FragmentManager fragmentManager = getSupportFragmentManager();
public void removeFragment(FragmentTag tag) {
Fragment fragmentRemove = fragmentManager.findFragmentByTag(tag.toString());
if (fragmentRemove != null) {
fragmentManager.beginTransaction()
.remove(fragmentRemove)
.commit();
// fix by #Ogbe
fragmentManager.popBackStackImmediate(tag.toString(),
FragmentManager.POP_BACK_STACK_INCLUSIVE);
}
}