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Android - How the state of views are preserved during Fragment Transforamtion

This confuses me a lot.
I had two fragments, and I use FragmentTransaction.replace() the swap the two fragments. State of some input controls like RadioGroup and checkbox is always preserved when I switch to the other fragments and switch back again.
.
I set break point on my OnCreateView() of Fragment, and every swap seems to trigger the method and new views are created each time. The savedInstanceBundle is always null as well. Since the new views are created, how do they get the state of the old views?
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_fieldsetup_marking, container, false);
// ...
return v;
}
This effect is fine for my app, but I just want to know how it is implemented.
where are the states stored?
Where is the android SDK code to restore this (I can not find any in the class FragmentTransection).

Android, return to specific fragment after a phone call made from the same fragment programatically

I have an activity with few fragments, out of which one fragment has a button which can be used to make a phone call from the app. Every thing is fine till this part, but what if I want to return the user to the same fragment in the app, with the same state as before the phone call, is it possible? I did have a look at one discussion on the stackoverflow. Here is the link
Link to answer for slightly similar question
It seems fine if I am making a call from activity and then return to that activity, but what can be done in case of fragments?

You should think of an Activity as a wrapper for your Fragments, so you just need to keep track of your currentfragment in your Activity and it's not an accident that built-in FragmentManager does this for you. So you only need to make sure that you will reuse previous Activity and not starting a new one.
You should be able to do that with Intent.FLAG_ACTIVITY_CLEAR_TOP

you can return same flagment.
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
// save flagment position
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
// set flagment position
}

Fragment save the state of a listener

In an Android Fragment, which is a part of a ViewPager, there is a ListView with EditText for filtering.
filterEditText = (EditText) view.findViewById(R.id.filter_friends);
filterEditText. addTextChangedListener(textWatcher);
When I navigate to another Fragment ondestroyview is called and then when I navigate back to this fragment onCreateView is called and the filtering doesn't work anymore, though the instance variables still exist.
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
view = inflater.inflate(R.layout.fragment_new_game_facebook, container,
false);
return view;
}
How this situation should be handled correctly?

You are probably using a FragmentStatePagerAdapter, which will destroy all non-active fragments to save memory. This is helpful for when you do not know how many fragments you will use until runtime, but is overly aggressive if you know which fragments will be in the pager. Try using a FragmentPagerAdapter instead, which will not destroy the fragments as soon as you navigate away from them, so you will not need to manually persist the state of each fragment and reload it.

Problems with views when reloading fragment

this is bit when i'm creating view,
public static int a=0;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
a++;
View view = inflater.inflate(R.layout.fragment_layout, container, false);
editText = (EditText) view.findViewById(R.id.amount);
TextView tv = (TextView) view.findViewById(R.id.textView1);
Button button = (Button) view.findViewById(R.id.addTransaction);
button.setOnClickListener(this); ///fragments implements OnClickListener
editText.setText(""+a);
tv.setText(""+a);
return view;
}
when i load this fragment first time, my editText is empty, but when i load fragment again, value in the editText is same like in previous execution.
Is anyone has idea what i'm doing wrong? And how i can fix it?
** EDIT
i modified little bit my code, now each time when i'm loading fragment a is incremented. and io noticed weird behaviour. tv has has actual value of a, while editText still has old value

You need to move the settext ( and probably some other stuff) into a later method in the fragment life cycle e.g. onActivityCreated.

Before adding the fragment try to get the fragment by calling FindFragmentByTag("tag"), i think you are adding new fragments on top of each other. Also add your fragment transaction to back state and then to check if more than one fragments are added, press back button. I had similar problem, and the reason was i kept adding new fragments in activity

Fragments are tied to activities, so my guess is that the activity is not being destroyed, which means your fragment is not being destroyed and instead "resumed". Perhaps you want that code in the onResume callback? Take a look at the Fragment lifecycle: Android Fragments

Access Activity within Fragment

Im making an App. And I want to access my 3 main activities into 3 different fragments. i use viewpager to swap activities but it only show layouts do not work on its functionality. Then i used Fragment to use functions. but my problem is same its only show layouts not is functions.
i made 3 different fragment for 3 activities and use
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.settings, container, false);
return v;
}
method.
idont know how to use onActivityCreated() method or getActivity(). please help me..
i search all of it about it but cannot done yet.. :(

To access Widget Of layout just use this
View.findViewById();