Difference between add replace and addToBackStack

Question

What is the main difference between calling these methods:

fragmentTransaction.addToBackStack(name);
fragmentTransaction.replace(containerViewId, fragment, tag);
fragmentTransaction.add(containerViewId, fragment, tag);

What does it mean to replace an already existing fragment, and adding a fragment to the activity state, and adding an activity to the back stack?

Secondly, with findFragmentByTag(), does this search for tag added by the add()/replace() method or the addToBackStack() method?

User · Answer

Here is a picture that shows the difference between add() and replace()

So add() method keeps on adding fragments on top of the previous fragment in FragmentContainer.

While replace() methods clears all the previous Fragment from Containers and then add it in FragmentContainer.

What is addToBackStack

addtoBackStack method can be used with add() and replace methods. It serves a different purpose in Fragment API.

What is the purpose?

Fragment API unlike Activity API does not come with Back Button navigation by default. If you want to go back to the previous Fragment then the we use addToBackStack() method in Fragment. Let's understand both

Case 1:

getSupportFragmentManager()
            .beginTransaction()
            .add(R.id.fragmentContainer, fragment, "TAG")
            .addToBackStack("TAG")
            .commit();

Case 2:

getSupportFragmentManager()
            .beginTransaction()
            .add(R.id.fragmentContainer, fragment, "TAG")
            .commit();

User · Answer

One more important difference between add and replace is this   replace removes the existing fragment and adds a new fragment  This means when you press back button the fragment that got replaced will be created with its onCreateView being invoked  Whereas add retains the existing fragments and adds a new fragment that means existing fragment will be active and they wont be in  paused  state hence when a back button is pressed onCreateView is not called for the existing fragment the fragment which was there before new fragment was added    In terms of fragment s life cycle events  onPause  onResume  onCreateView and other life cycle events will be invoked in case of replace but they wont be invoked in case of add    Edit  One should be careful if she is using some kind of event bus library like Greenrobot s Eventbus and reusing the same fragment to stack the fragment on top of other via  add  In this scenario  even though you follow the best practice and register the event bus in onResume and unregister in onPause  event bus would still be active in each instance of the added fragment as add fragment wont call either of these fragment life cycle methods  As a result event bus listener in each active instance of the fragment would process the same event which may not be what you want

User · Answer

Example an activity have 2 fragments and we use FragmentManager to replace/add with addToBackstack each fragment to a layout in activity

Use replace

Go Fragment1

Fragment1: onAttach
Fragment1: onCreate
Fragment1: onCreateView
Fragment1: onActivityCreated
Fragment1: onStart
Fragment1: onResume

Go Fragment2

Fragment2: onAttach
Fragment2: onCreate
Fragment1: onPause
Fragment1: onStop
Fragment1: onDestroyView
Fragment2: onCreateView
Fragment2: onActivityCreated
Fragment2: onStart
Fragment2: onResume

Pop Fragment2

Fragment2: onPause
Fragment2: onStop
Fragment2: onDestroyView
Fragment2: onDestroy
Fragment2: onDetach
Fragment1: onCreateView
Fragment1: onStart
Fragment1: onResume

Pop Fragment1

Fragment1: onPause
Fragment1: onStop
Fragment1: onDestroyView
Fragment1: onDestroy
Fragment1: onDetach

Use add

Go Fragment1

Fragment1: onAttach
Fragment1: onCreate
Fragment1: onCreateView
Fragment1: onActivityCreated
Fragment1: onStart
Fragment1: onResume

Go Fragment2

Fragment2: onAttach
Fragment2: onCreate
Fragment2: onCreateView
Fragment2: onActivityCreated
Fragment2: onStart
Fragment2: onResume

Pop Fragment2

Fragment2: onPause
Fragment2: onStop
Fragment2: onDestroyView
Fragment2: onDestroy
Fragment2: onDetach

Pop Fragment1

Fragment1: onPause
Fragment1: onStop
Fragment1: onDestroyView
Fragment1: onDestroy
Fragment1: onDetach

Sample project

User · Answer

Important thing to be noticed   Difference between Replace and Replace with backstack is whenever we use only replace then the fragment is destroyed   ondestroy   is called   and when we use replace with backstack then fragments onDestroy   is not called   i e when back button is pressed fragment is invoked with its onCreateView

User · Answer

Basic difference between add   and replace   can be described as    add   is used for simply adding a fragment to some root element  replace   behaves similarly but at first it removes previous fragments and then adds next fragment    We can see the exact difference when we use addToBackStack   together with add   or replace     When we press back button after in case of add      onCreateView is never called  but in case of replace    when we press back button     oncreateView is called every time

User · Answer

When We Add First Fragment --  Second Fragment using add   method    btn one setOnClickListener new View OnClickListener                  Override             public void onClick View v                    Toast makeText getActivity    Click First  Fragment  Toast LENGTH LONG  show                     Fragment fragment   new SecondFragment                    getActivity   getSupportFragmentManager   beginTransaction                            add R id fragment frame  fragment  fragment getClass   getSimpleName    addToBackStack null  commit                               replace R id fragment frame  fragment  fragment getClass   getSimpleName    addToBackStack null  commit                                 When we use add   in fragment   E Keshav  SecondFragment  onAttach E Keshav  SecondFragment  onCreate E Keshav  SecondFragment  onCreateView E Keshav  SecondFragment  onActivityCreated E Keshav  SecondFragment  onStart E Keshav  SecondFragment  onResume   When we use replace   in fragment  going to first fragment to second fragment in  First -- Second using replace   method   btn one setOnClickListener new View OnClickListener                  Override             public void onClick View v                    Toast makeText getActivity    Click First Fragment  Toast LENGTH LONG  show                     Fragment fragment   new SecondFragment                    getActivity   getSupportFragmentManager   beginTransaction                              add R id fragment frame  fragment  fragment getClass   getSimpleName    addToBackStack null  commit                             replace R id fragment frame  fragment  fragment getClass   getSimpleName    addToBackStack null  commit                                E Keshav  SecondFragment  onAttach E Keshav  SecondFragment  onCreate  E Keshav  FirstFragment  onPause -------------------------- FirstFragment E Keshav  FirstFragment  onStop --------------------------- FirstFragment E Keshav  FirstFragment  onDestroyView -------------------- FirstFragment  E Keshav  SecondFragment  onCreateView E Keshav  SecondFragment  onActivityCreated E Keshav  SecondFragment  onStart E Keshav  SecondFragment  onResume   In case of Replace First Fragment these method is extra called   onPause onStop onDestroyView  is extra called    E Keshav  FirstFragment  onPause  E Keshav  FirstFragment  onStop  E Keshav  FirstFragment  onDestroyView

User · Answer

1  fragmentTransaction addToBackStack str    Description - Add this transaction to the back stack  This means that the transaction will be remembered after it is committed  and will reverse its operation when later popped off the stack   2  fragmentTransaction replace int containerViewId  Fragment fragment  String tag   Description - 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   3  fragmentTransaction add int containerViewId  Fragment fragment  String tag   Description - Add a fragment to the activity state  This fragment may optionally also have its view  if Fragment onCreateView returns non-null  into a container view of the activity      What does it mean to replace an already existing fragment  and adding   a fragment to the activity state and adding an activity to the back   stack     There is a stack in which all the activities in the running state are kept  Fragments belong to the activity  So you can add them to embed them in a activity   You can combine multiple fragments in a single activity to build a multi-pane UI and reuse a fragment in multiple activities  This is essentially useful when you have defined your fragment container at different layouts  You just need to replace with any other fragment in any layout   When you navigate to the current layout  you have the id of that container to replace it with the fragment you want    You can also go back to the previous fragment in the backStack with the popBackStack   method  For that you need to add that fragment in the stack using addToBackStack   and then commit   to reflect  This is in reverse order with the current on top      findFragmentByTag does this search for tag added by the add replace   method or the addToBackStack method     If depends upon how you added the tag  It then just finds a fragment by its tag that you defined before either when inflated from XML or as supplied when added in a transaction   References  FragmentTransaction

User · Answer

The FragmentManger s function add and replace can be described as these 1  add means it will add the fragment in the fragment back stack and it will show at given frame you are providing like   getFragmentManager beginTransaction add R id contentframe Fragment1 newInstance   null   2 replace means that you are replacing the fragment with another fragment at the given frame  getFragmentManager beginTransaction replace R id contentframe Fragment1 newInstance   null   The Main utility between the two is that when you are back stacking the replace will refresh the fragment but add will not refresh previous fragment

User · Answer

Although it is an old question already answered, maybe those next examples can complement the accepted answer and they can be useful for some new programmers in Android as I am.

Option 1 - "addToBackStack()" is never used

Case 1A - adding, removing, and clicking Back button

Activity :      onCreate() - onStart() - onResume()                             Activity is visible
add Fragment A :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment A is visible
add Fragment B :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment B is visible
add Fragment C :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment C is visible
remove Fragment C :     onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               Fragment B is visible
(Back button clicked)
Activity :      onPause() - onStop() - onDestroy()
Fragment A :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()
Fragment B :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               App is closed, nothing is visible

Case 1B - adding, replacing, and clicking Back button

Activity :      onCreate() - onStart() - onResume()                             Activity is visible
add Fragment A :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment A is visible
add Fragment B :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment B is visible
(replace Fragment C)    
Fragment B :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               
Fragment A :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()
Fragment C :        onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment C is visible
(Back button clicked)
Activity :      onPause() - onStop() - onDestroy()
Fragment C :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               App is closed, nothing is visible

Option 2 - "addToBackStack()" is always used

Case 2A - adding, removing, and clicking Back button

Activity :      onCreate() - onStart() - onResume()                             Activity is visible
add Fragment A :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment A is visible
add Fragment B :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment B is visible
add Fragment C :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment C is visible
remove Fragment C :     onPause() - onStop() - onDestroyView()                              Fragment B is visible
(Back button clicked)
Fragment C :        onCreateView() - onActivityCreated() - onStart() - onResume()                   Fragment C is visible
(Back button clicked)
Fragment C :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               Fragment B is visible
(Back button clicked)
Fragment B :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               Fragment A is visible
(Back button clicked)
Fragment A :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               Activity is visible
(Back button clicked)
Activity :      onPause() - onStop() - onDestroy()                              App is closed, nothing is visible

Case 2B - adding, replacing, removing, and clicking Back button

Activity :      onCreate() - onStart() - onResume()                             Activity is visible
add Fragment A :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment A is visible
add Fragment B :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment B is visible
(replace Fragment C)    
Fragment B :        onPause() - onStop() - onDestroyView()  
Fragment A :        onPause() - onStop() - onDestroyView() 
Fragment C :        onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment C is visible
remove Fragment C :     onPause() - onStop() - onDestroyView()                              Activity is visible
(Back button clicked)
Fragment C :        onCreateView() - onActivityCreated() - onStart() - onResume()                   Fragment C is visible
(Back button clicked)
Fragment C :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               
Fragment A :        onCreateView() - onActivityCreated() - onStart() - onResume()   
Fragment B :        onCreateView() - onActivityCreated() - onStart() - onResume()                   Fragment B is visible
(Back button clicked)
Fragment B :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               Fragment A is visible
(Back button clicked)
Fragment A :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               Activity is visible
(Back button clicked)
Activity :      onPause() - onStop() - onDestroy()                              App is closed, nothing is visible

Option 3 - "addToBackStack()" is not used always (in the below examples, w/o indicates that it is not used)

Case 3A - adding, removing, and clicking Back button

Activity :      onCreate() - onStart() - onResume()                             Activity is visible
add Fragment A :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment A is visible
add Fragment B w/o:     onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment B is visible
add Fragment C w/o:     onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment C is visible
remove Fragment C :     onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               Fragment B is visible
(Back button clicked)
Fragment B :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               
Fragment A :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               Activity is visible
(Back button clicked)
Activity :      onPause() - onStop() - onDestroy()                              App is closed, nothing is visible

Case 3B - adding, replacing, removing, and clicking Back button

Activity :      onCreate() - onStart() - onResume()                             Activity is visible
add Fragment A :    onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment A is visible
add Fragment B w/o:     onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment B is visible
(replace Fragment C)    
Fragment B :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()   
Fragment A :        onPause() - onStop() - onDestroyView() 
Fragment C :        onAttach() - onCreate() - onCreateView() - onActivityCreated() - onStart() - onResume()     Fragment C is visible
remove Fragment C :     onPause() - onStop() - onDestroyView()                              Activity is visible
(Back button clicked)
Fragment C :        onCreateView() - onActivityCreated() - onStart() - onResume()                   Fragment C is visible
(Back button clicked)
Fragment C :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               
Fragment A :        onCreateView() - onActivityCreated() - onStart() - onResume()                   Fragment A is visible
(Back button clicked)
Fragment A :        onPause() - onStop() - onDestroyView() - onDestroy() - onDetach()               Activity is visible
(Back button clicked)
Activity :      onPause() - onStop() - onDestroy()                              App is closed, nothing is visible

[android] Difference between add(), replace(), and addToBackStack()

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