android fragment- How to save states of views in a fragment when another fragment is pushed on top of it

Question

In android  a fragment  say FragA  gets added to the backstack and another fragment  say FragB  comes to the top  Now on hitting back FragA comes to the top and the onCreateView   is called  Now I had FragA in a particular state before FragB got pushed on top of it    My Question is how can I restore FragA to its previous state   Is there a way to save state  like say in a Bundle  and if so then which method should I override

User · Answer

The Best Solution I found is below   onSavedInstanceState    always called inside fragment when activity is going to shut down Move activity from one to another or config changes    So if we are calling multiple fragments on same activity then We have to use the following approach   Use OnDestroyView   of the fragment and save the whole object inside that method  Then OnActivityCreated    Check that if object is null or not Because this method calls every time   Now restore state of an object here   Its works always

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I used a hybrid approach for fragments containing a list view  It seems to be performant since I don t replace the current fragment but rather add the new fragment and hide the current one  I have the following method in the activity that hosts my fragments   public void addFragment Fragment currentFragment  Fragment targetFragment  String tag        FragmentManager fragmentManager   getSupportFragmentManager        FragmentTransaction transaction   fragmentManager beginTransaction        transaction setCustomAnimations 0 0 0 0       transaction hide currentFragment          use a fragment tag  so that later on we can find the currently displayed fragment     transaction add R id frame layout  targetFragment  tag               addToBackStack tag               commit        I use this method in my fragment  containing the list view  whenever a list item is clicked tapped  and thus I need to launch display the details fragment    FragmentManager fragmentManager   getActivity   getSupportFragmentManager    SearchFragment currentFragment    SearchFragment  fragmentManager findFragmentByTag getFragmentTags   0    DetailsFragment detailsFragment   DetailsFragment newInstance  some object containing some details      MainActivity  getActivity    addFragment currentFragment  detailsFragment   Details      getFragmentTags   returns an array of strings that I use as tags for different fragments when I add a new fragment  see transaction add method in addFragment method above    In the fragment containing the list view  I do this in its onPause   method    Override public void onPause            keep the list view s state in memory   save  it          before adding a new fragment or replacing current fragment with a new one     ListView lv     ListView  getActivity   findViewById R id listView       mListViewState   lv onSaveInstanceState        super onPause        Then in onCreateView of the fragment  actually in a method that is invoked in onCreateView   I restore the state      Restore previous state  including selected item index and scroll position  if mListViewState    null        Log d TAG   Restoring the listview s state         lv onRestoreInstanceState mListViewState

User · Answer

A simple way of keeping the values of fields in different fragments in an activity  Create the Instances of fragments and add instead of replace and remove      FragA  fa  new FragA        FragB  fb  new FragB        FragC  fc  new FragB        fragmentManager   getSupportFragmentManager        fragmentTransaction   fragmentManager beginTransaction        fragmentTransaction add R id fragmnt container  fa       fragmentTransaction add R id fragmnt container  fb       fragmentTransaction add R id fragmnt container  fc       fragmentTransaction show fa       fragmentTransaction hide fb       fragmentTransaction hide fc       fragmentTransaction commit      Then just show and hide the fragments instead of adding and removing those again      fragmentTransaction   fragmentManager beginTransaction        fragmentTransaction hide fa       fragmentTransaction show fb       fragmentTransaction hide fc       fragmentTransaction commit

User · Answer

I worked with an issue very similar to this  Since I knew I would frequently be returning back to a previous fragment  I checked to see whether the fragment  isAdded   was true  and if so  rather than doing a transaction replace   I just do a transaction show     This keeps the fragment from being recreated if it s already on the stack - no state saving needed   Fragment target    lt my fragment gt   FragmentTransaction transaction   getFragmentManager   beginTransaction    transaction setTransition FragmentTransaction TRANSIT FRAGMENT OPEN   if target isAdded          transaction show target     else       transaction addToBackStack button id    stack item        transaction replace R id page fragment  target     transaction commit      Another thing to keep in mind is that while this preserves the natural order for fragments themselves  you might still need to handle the activity itself being destroyed and recreated on orientation  config  change   To get around this in AndroidManifest xml for your  node   android configChanges  orientation screenSize    In Android 3 0 and higher  the screenSize is apparently required   Good luck

User · Answer

Just inflate your View for once    Exemple follows   public class AFragment extends Fragment    private View mRootView   Nullable  Override public View onCreateView LayoutInflater inflater  ViewGroup container  Bundle savedInstanceState        if mRootView  null           mRootView   inflater inflate R id fragment a  container  false                              return mRootView

User · Answer

In the end after trying many of these complicated solutions as I only needed to save restore a single value in my Fragment  the content of an EditText   and although it might not be the most elegant solution  creating a SharedPreference and storing my state there worked for me

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private ViewPager viewPager  viewPager    ViewPager  findViewById R id pager   mAdapter   new TabsPagerAdapter getSupportFragmentManager     viewPager setAdapter mAdapter   viewPager setOnPageChangeListener new ViewPager OnPageChangeListener               Override         public void onPageSelected int position                   on changing the page                make respected tab selected             actionBar setSelectedNavigationItem position                       Override         public void onPageScrolled int arg0  float arg1  int arg2                        Override         public void onPageScrollStateChanged int arg0                          Override public void onTabReselected Tab tab  FragmentTransaction ft        Override public void onTabSelected Tab tab  FragmentTransaction ft           on tab selected        show respected fragment view     viewPager setCurrentItem tab getPosition         Override public void onTabUnselected Tab tab  FragmentTransaction ft

User · Answer

In fragment guide FragmentList example you can find    Override public void onSaveInstanceState Bundle outState        super onSaveInstanceState outState       outState putInt  curChoice   mCurCheckPosition       Which you can use later like this    Override public void onActivityCreated Bundle savedInstanceState        super onActivityCreated savedInstanceState       if  savedInstanceState    null               Restore last state for checked position          mCurCheckPosition   savedInstanceState getInt  curChoice   0             I m a beginner in Fragments but it seems like solution of your problem    OnActivityCreated is invoked after fragment returns from back stack

User · Answer

if you are handling the config changes in your fragment activity specified in android manifest like this   lt activity     android name   courses posts EditPostActivity      android configChanges  keyboardHidden orientation      android screenOrientation  unspecified    gt    then the onSaveInstanceState of the fragment will not be invoked and the savedInstanceState object will always be null

User · Answer

i donot think onSaveInstanceState is a good solution  it just use for activity which had been destoryed   From android 3 0 the Fragmen has been manager by FragmentManager  the condition is  one activity mapping manny fragments  when the fragment is added not replace  it will recreated  in backStack  the view will be destored  when back to the last one  it will display as before   So i think the fragmentManger and transaction is good enough to handle it

User · Answer

Just notice that if you work with Fragments using ViewPager  it s pretty easy  You only need to call this method  setOffscreenPageLimit     Accordign to the docs      Set the number of pages that should be retained to either side of the current page in the view hierarchy in an idle state  Pages beyond this limit will be recreated from the adapter when needed    Similar issue here

User · Answer

Fragment s onSaveInstanceState Bundle outState  will never be called unless fragment s activity call it on itself and attached fragments  Thus this method won t be called until something  typically rotation  force activity to SaveInstanceState and restore it later   But if you have only one activity and large set of fragments inside it  with intensive usage of replace   and application runs only in one orientation activity s onSaveInstanceState Bundle outState  may not be called for a long time   I know three possible workarounds   The first   use fragment s arguments to hold important data   public class FragmentA extends Fragment       private static final String PERSISTENT VARIABLE BUNDLE KEY    persistentVariable        private EditText persistentVariableEdit       public FragmentA             setArguments new Bundle                 Override     public View onCreateView LayoutInflater inflater  ViewGroup container  Bundle savedInstanceState            View view   inflater inflate R layout fragment a  null            persistentVariableEdit    EditText  view findViewById R id editText            TextView proofTextView    TextView  view findViewById R id textView            Bundle mySavedInstanceState   getArguments            String persistentVariable   mySavedInstanceState getString PERSISTENT VARIABLE BUNDLE KEY            proofTextView setText persistentVariable             view findViewById R id btnPushFragmentB  setOnClickListener new View OnClickListener                  Override             public void onClick View v                    getFragmentManager                            beginTransaction                            replace R id frameLayout  new FragmentB                             addToBackStack null                           commit                                       return view              Override     public void onPause             super onPause            String persistentVariable   persistentVariableEdit getText   toString             getArguments   putString PERSISTENT VARIABLE BUNDLE KEY  persistentVariable             The second but less pedantic way - hold variables in singletons   The third - don t replace   fragments but add   show   hide   them instead

[android] android fragment- How to save states of views in a fragment when another fragment is pushed on top of it

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