Develop Reference

Android fragment lifecycle when bringing fragment back from background

Scenario: fragment is visible, user minimises the app and brings it back from background.
Why onCreateView onCreate is not being called and it jumps straight to calling onStart?
When is onCreate onCreateView called? How to restore fragment data if it jumps straight to onStart?

as stated here:
https://developer.android.com/guide/components/fragments#Lifecycle
"The fragment isn't visible. Either the host activity has been stopped or the fragment has been removed from the activity but added to the back stack. A stopped fragment is still alive (all state and member information is retained by the system). However, it is no longer visible to the user and is killed if the activity is killed."
And you can save the data using the OnSaveInstanceState(Bundle) on the onStart() method

how to call OnResume and Onpause methods in fragment?

i have two fragments A and B.here I am Replacing fragment B from A And then fragment A from B in between i am showing toast in onPause method and onResume method but some how its not working could any one explain me why with code ?

The fragments onResume() or onPause() will be called only when the Activities onResume() or onPause() is called. They are tightly coupled to the Activity.
Managing the lifecycle of a fragment is a lot like managing the lifecycle of an activity.
Resumed :->
The fragment is visible in the running activity.
Paused :->
Another activity is in the foreground and has focus, but the activity in which this fragment lives is still visible (the foreground activity is partially transparent or doesn't cover the entire screen).
Stopped :->
The fragment is not visible. Either the host activity has been stopped or the fragment has been removed from the activity but added to the back stack. A stopped fragment is still alive (all state and member information is retained by the system). However, it is no longer visible to the user and will be killed if the activity is killed.
for more information read from android docs

Will Activity onpause be called when switching between fragments

Right now I have 2 activities. When the second activity is running, the first activity onpause is clicked which means I have to unregister all the listeners (which is not what I want when the app is running, I just wanted them unregistered when the app is in the background).
So would it make sense for me to create 2 fragments with one activity. Then I can unregister the listener when the activity onpause is called (only when app goes to background) but it won't be called when fragments are switched.
Is my understanding correct?
Thank you

This totally depends on the activity that you have used to launch your fragment . If two fragments A and B belong to the same activity, then the moment you switch view from Fragment A to Fragment B, your activity does not go to a paused state, means onPause() won't be called, but is still running which is ideally providing the view for Fragment B.
So, you do not need to unregister the listener on change of Fragment in the same activity.
Please correct me if I am wrong.

Yups Activity onPause() would not be called when switching fragments.

onDetach not called for fragment?

I write an code to launch Activity A to Activity B. Both Activity A and B has fragment implementation.
Scenario: If Activity A frequently launch Activity B which contain Fragment, then most of times it missed Fragment.onDetach..I checked with log, normally it give me following override method log:
onAttach
List item
OnCreatView
onViewCreate then press device Back Button
onPause
onStop
onDestroyView
onDetach
now I press device Back button from Activity B which again launch Activity A then it launch Activity B and repeat same sequence frequently, then log sequence get change in following order:
onAttach
List item
OnCreatView
onViewCreate then press device Back Button
onPause
onStop
onDestroyView and repeat with
onAttach without onDetach
some times it repeat same behaviour after onPause also.
I am using
getSupportFragmentManager().beginTransaction()
.replace(R.id.fragment_container, fragment).addToBackStack(null).commitAllowingStateLoss(); to add fragment in Activity.
Is there anything I am missing..any suggestion ?

A fragment is detached after it is destroyed. what u have done is dettached directly after destroying view.
Remember destroying and destroying view are two different things in fragment.
So try onDestroyView, then onDestroy and then onDetach.

android -does calling finish from activity destroy hosted fragment?

I have an 'Activity A' which host a 'Fragment B'. Please confirm that if I call A.finish() then 'fragment B 'gets destroyed. The fragment B would already be added to the fragment manager. I realize that a fragment is a sub-activity but i want to know do i have to tell the fragment manager to release the fragment in Ondestroy or is it all taken care of ?

but i want to know do i have to tell the fragment manager to
release the fragment in Ondestroy or is it all taken care of ?
By default when you call finish in your activity it will automatically call onDestroy method of all the fragments that is attach to the activity thus destroying it, so no need to worry about destroying the fragment in onDestroy method of your activity.
From the documentation:
For example, when the activity is paused, so are all fragments in it,
and when the activity is destroyed, so are all fragments.

Fragments are the Subactivities of an activity. So whenever we will call the finish the fragment associated with it will also get destroyed without notifying FragmentManager.

Yes the fragment is destroyed. From the Android Fragment guide:
For example, when the activity is paused, so are all fragments in it,
and when the activity is destroyed, so are all fragments.