Having a flow to add fragment and later replace() fragment. All fragment are dynamically added, but not all call addToBackStack().
getSupportFragmentManager().beginTransaction()
.add(R.id.frgment_holder, frgmtA, frgmtA.NAME)
.commit();
and in somewhere it could add another, like:
getSupportFragmentManager().beginTransaction()
.replace(R.id.frgment_holder, frgmtB)
.addToBackStack(frgmtB.NAME)
.commit();
the replace() with the frgmtB will remove the frgmtA from the container R.id.frgment_holder.
if press back button at this state, it will pop the frgmtB. But will it recreate the frgmtA even if it did not call addToBackStack() when did the adding?
if in the flow of adding fragment into same container with a serials mixed add() and replace() calls, and someone call addToBackStack() but someone do not, how would the back button behavior?
EDIT:
after
getSupportFragmentManager().beginTransaction()
.replace(R.id.frgment_holder, frgmtB)
.addToBackStack(frgmtB.NAME)
.commit();
will the
getSupportFragmentManager().findFragmentByTag(frgmtA.NAME);
still find the the frgmtA? what if when add frgmtA also called addToBackStack();
The doc says "This first searches through fragments that are currently added to the manager's activity; if no such fragment is found, then all fragments currently on the back stack are searched."
The case would be
adding frgmtA; not call add to stack; UI state changed here;
(what if the frgmtA is not dynamically added by add(), but sepcified in layout file with class="frgmtA"?).
replace() with frgmtB; addToStack();
replace() with frgmtC; addToStack();
then if the stackTop is frgmtC, would like the back button press to bring back the first frgmtA with its last UI state.
1.
.add(R.id.frgment_holder, frgmtA, frgmtA.NAME)
.commit();
.replace(R.id.frgment_holder, frgmtB, frgmtB.NAME)
.addToBackStack(frgmtB.NAME)
.commit();`
the replace will remove the frgmtA from the the holder and its onDestroyView will be called (but since it is referenced in the backstack’s transaction data, frgmtA is NOT destroyed). And the frgmtB will be added to the holder.
Since the frgmtA is not destroyed, the
getSupportFragmentManager().findFragmentByTag(frgmtA.NAME);
will find it.
after then, press on back button, it will pop the top transaction from the backStack, then reversing the transaction. i.e. remove frgmtB from the holder and add frgmtA back to the holder. Since there is no more reference to frgmtB its onDestroy is called.
2.
in the case of
add frgmtA;
replace() with frgmtB; addToStack();
replace() with frgmtC; addToStack();
If want to back press to jump to frgmtA, need to override onBackPressed(), in it
do
popBackStack(frgmtB.NAME, POP_BACK_STACK_INCLUSIVE),
which will toss out the transaction in the stack above stack entry named frgmtB.NAME and do reverse the transaction on it, which will add back the frgmtA in the holder.
Unless you interfere with the Back button logic using onBackPressed() or addOnBackStackChangedListener(), things are straight forward
if you add a fragment through addToBackStack(), it will be removed when Back is tapped
if there are no other fragments left in the back stack, app will be closed
try this anyone line as your demand
its 4 differnt lines code you have checked
getActivity().getSupportFragmentManager().popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
getActivity().getSupportFragmentManager().popBackStackImmediate(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
FragmentTransaction transaction = getActivity().getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.framelayout, fragment);
transaction.addToBackStack(null);
getActivity().getSupportFragmentManager().popBackStack();
Related
My app has 3 UI levels, each level has its own fragment, A -> B -> C.
I wish to optionally allow my app user to navigate straight to the top level fragment i.e. from C -> A without invoking B.
i.e., I still want to allow the user to go from C->B if they press the back button, but in the C fragment, I have a "Home" button, which takes them directly to A. This is the operation where I want to flush the backstack.
Additionally, I want the user to be able to go from B->A using the back button, hence I'm adding A and B both to the backstack.
I have tried the options from this SO post but in each case, onCreateView gets invoked for each fragment, even if I use fm_.popBackStackImmediate(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
Also checked this thread, it seems to recommend using popBackStackImmediate(null, FragmentManager.POP_BACK_STACK_INCLUSIVE)
Can anyone please suggest a way to pop the entire backstack without having the onCreateView called on popped fragments?
Dont add backStack line for going from fragment B->C
while going from A->B use
HighlightFragment highlightFragment=new HighlightFragment(FirstReaderScreen.this);
getSupportFragmentManager()
.beginTransaction()
.add(R.id.LL_Fragment, highlightFragment) // LL_Fragment is container
.addToBackStack(null)
.commit();
while going B->C use
HighlightFragment highlightFragment=new HighlightFragment(FirstReaderScreen.this);
getSupportFragmentManager()
.beginTransaction()
.add(R.id.LL_Fragment, highlightFragment)
.commit();
dont add line .addtobackstack(null)
This worked for me
i estimate you're using replace fragment.
try to use begintransaction.hide / show to manage many fragment inside 1 activity if you don want to popback
//on Activity
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(containerId, new FragmentA(), fragmentA.getClass().getSimpleName());
fragmentTransaction.commit();
//inside fragment A to jump fragment without PopBackStack
getFragmentManager().beginTransaction().hide(this).commit();
getFragmentManager().beginTransaction().show(new FragmentB()).commit();
This is working for me when needing to clear the back stack for tab switches in BottomNavigationView
public void clearBackStack() {
int backStackEntryCount = mFragmentActivity
.getSupportFragmentManager()
.getBackStackEntryCount();
for (int i = 0; i < backStackEntryCount; i++) {
mFragmentActivity.getSupportFragmentManager().popBackStack();
}
}
I need to detect backbutton pressed in Fragment.
My app start download data in Fragment, so I need to stop download (also do some operations) on back button pressed, and dont need if home button pressed. So I cant use onPause(), because its called in both cases.
I use addToBackStack(null), but I need to do some operations (stop download and ) in current fragment and then return to previous fragment.
getSupportFragmentManager()
.beginTransaction()
.replace(R.id.content_frame, fragment)
.addToBackStack(null)
.commit();
When you are done with the things you want to do in the fragment you could use something like this to remove the current fragment. If last fragment was added to the stack (as you mentioned) then removing current fragment will automatically display last fragment.
this.getActivity().getSupportFragmentManager().beginTransaction()
.remove(this).commit();
or
this.getActivity().getFragmentManager().beginTransaction()
.remove(this).commit();
Look at this link
On yout activity you can overide onBackPressed() et then call popBackStack
I add, show and hide fragments. Each time I add/show a fragment, I hide the previous fragment and add the transaction to the backstack.
When a user presses the back button, a fragment is popped and I would like to have a reference to it.
Why do I need a reference? So I could hide it when the user continues to the next fragment.
So, how do I get a reference to a popped fragment?
EDIT-25-04-2013:
Here's code to explain how to add a new fragment, while hiding the previous one. The question is how to get a reference to the last fragment after it is popped from the backstack (using the back button)?
FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
fragmentTransaction.hide(lastFragment);
fragmentTransaction.add(newFragment);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
lastFragment = newFragment;
I use generated tags for each fragment, save the tags in a stack and persist the stack. This way I get hold of every fragment out there - last one in specific.
See the code here.
I'm trying to decide and show a fragment in activity's onResume method, but in case a previously added fragment is chosen again, then the activity goes blank.
Sample code (with one fragment):
#Override
protected void onResume(){
FragmentTransaction trans = getSupportFragmentManager().beginTransaction();
trans.replace(R.id.myLayout, fragA);
trans.commit();
getSupportFragmentManager().executePendingTransactions();
}
With above code, when the activity is created for the first time, it shows fragA correctly, but in case I press Home Key and then switch back to my activity (in order to provoke onResume again), it all goes blank (seems like fragA is removed).
Is replacing a previously added fragment removes itself? or how not to loose a fragment if it is replaced by itself?
You can't replace a fragment with itself. The first half of a replace is a removal of the previous fragment at that id. Once a fragment is removed it can no longer be added or used by the fragment manager (so the add portion of the replace will not work properly).
Depending on your use case, you have two options:
Create a new fragment instead of reusing the existing instance
Use some other method to see if its necessary to replace your fragment
Finally, you probably don't need to call executePendingTransactions.
You can try:
if( !(getSupportFragmentManager().findFragmentById(R.id.myLayout) instanceof FragmentA) ) {
FragmentTransaction trans = getSupportFragmentManager().beginTransaction();
trans.replace(R.id.myLayout, fragA);
trans.commit();
}
And I assume that fragA is FragmentA class object.
Finally, I had to put a check before replacing fragments. In case, an (already added) fragment is requested for replace again, I had to check if its already added then ignore the replacement, else proceed. For example:
#Override
protected void onResume() {
if (!fragA.isAdded()) {
FragmentTransaction trans = getSupportFragmentManager().beginTransaction();
trans.replace(R.id.myLayout, fragA);
trans.commit();
//getSupportFragmentManager().executePendingTransactions(); //unnecessary
}
}
When referencing back to a created Fragment please do make sure to try adding the
fragmentTransaction.addToBackStack(null);
method right before committing so that your Fragment is resumed instead of destroyed as mentioned in the developer guides.
If you don't call addToBackStack() when you perform a transaction that removes a fragment, then that fragment is destroyed when the transaction is committed and the user cannot navigate back to it. Whereas, if you do call addToBackStack() when removing a fragment, then the fragment is stopped and is later resumed if the user navigates back.
You can find this at the end of this page.
I have Fragment1. On them, i pressed button and start DialogFramgent. On DialogFragment i pressed button and start Fragment2. When i pressed back, i am return to Fragment1, but not to DialogFragmnet
You can add the fragment to the backstack. A call addToBackStack() should solve the problem. Straight from the documentation: "This back stack is managed by the activity and allows the user to return to the previous fragment state, by pressing the Back button". See for details:
http://developer.android.com/guide/components/fragments.html
Jasper
A great feature about using fragments in your activity is the ability to add, remove, replace, and perform other actions with them, in response to user interaction. Each set of changes that you commit to the activity is called a transaction and you can perform one using APIs in FragmentTransaction. You can also save each transaction to a back stack managed by the activity, allowing the user to navigate backward through the fragment changes (similar to navigating backward through activities).
You can acquire an instance of FragmentTransaction from the FragmentManager like this:
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
Each transaction is a set of changes that you want to perform at the same time. You can set up all the changes you want to perform for a given transaction using methods such as add(), remove(), and replace(). Then, to apply the transaction to the activity, you must call commit().
Before you call commit(), however, you might want to call addToBackStack(), in order to add the transaction to a back stack of fragment transactions. This back stack is managed by the activity and allows the user to return to the previous fragment state, by pressing the Back button.