Android - save restore fragment state

Question

I have an Activity in which I go through several fragments  In every fragment I have several views  EditText  ListView  Map  etc    How can I save the instance of the fragment that is shown at that moment  I need it to work when the activity is onPause   -- gt  onResume    Also I need it to work when I return from another fragment  pop from backstack    From the main Activity I call the first fragment  then from the the fragment I call the next one   Code for my Activity   public class Activity Main extends FragmentActivity   public static Fragment 1 fragment 1  public static Fragment 2 fragment 2  public static Fragment 3 fragment 3  public static FragmentManager fragmentManager    Override  protected void onCreate Bundle savedInstanceState        super onCreate savedInstanceState       setContentView R layout main         fragment 1   new Fragment 1          fragment 2   new Fragment 2          fragment 3   new Fragment 3          fragmentManager   getSupportFragmentManager         FragmentTransaction transaction 1   fragmentManager beginTransaction         transaction 1 replace R id content frame  fragment 1        transaction 1 commit         Then here is the code for one of my fragments   public class Fragment 1 extends Fragment          private EditText title        private Button go next           Override       public View onCreateView final LayoutInflater inflater          ViewGroup container  Bundle savedInstanceState                 View rootView   inflater inflate R layout fragment 1              container  false                title    EditText  rootView findViewById R id title                go next    Button  rootView findViewById R id go next                image setOnClickListener new View OnClickListener                Override          public void onClick View v                      FragmentTransaction transaction 2   Activity Main fragmentManager                  beginTransaction                      transaction 2 replace R id content frame                    Activity Main fragment 2                    transaction 2 addToBackStack null                    transaction 2 commit                                    I have searched a lot of information but nothing clear  Can somebody give a clear solution and an example  please

User · Answer

When a fragment is moved to the backstack, it isn't destroyed. All the instance variables remain there. So this is the place to save your data. In onActivityCreated you check the following conditions:

Is the bundle != null? If yes, that's where the data is saved (probably orientation change).
Is there data saved in instance variables? If yes, restore your state from them (or maybe do nothing, because everything is as it should be).
Otherwise your fragment is shown for the first time, create everything anew.

Edit: Here's an example

public class ExampleFragment extends Fragment {
    private List<String> myData;

    @Override
    public void onSaveInstanceState(final Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putSerializable("list", (Serializable) myData);
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);

        if (savedInstanceState != null) {
            //probably orientation change
            myData = (List<String>) savedInstanceState.getSerializable("list");
        } else {
            if (myData != null) {
                //returning from backstack, data is fine, do nothing
            } else {
                //newly created, compute data
                myData = computeData();
            }
        }
    }
}

User · Answer

You can get current Fragment from fragmentManager  And if there are non of them in fragment manager you can create Fragment 1  public class MainActivity extends FragmentActivity         public static Fragment 1 fragment 1      public static Fragment 2 fragment 2      public static Fragment 3 fragment 3      public static FragmentManager fragmentManager         Override     protected void onCreate Bundle arg0            super onCreate arg0           setContentView R layout main            fragment 1    Fragment 1  fragmentManager findFragmentByTag  fragment1             fragment 2    Fragment 2  fragmentManager findFragmentByTag  fragment2             fragment 3    Fragment 3  fragmentManager findFragmentByTag  fragment3              if fragment 1  null  amp  amp  fragment 2  null  amp  amp  fragment 3  null                          fragment 1   new Fragment 1                          fragmentManager beginTransaction   replace R id content frame  fragment 1   fragment1   commit                            also you can use setRetainInstance to true what it will do it ignore onDestroy   method in fragment and your application going to back ground and os kill your application to allocate more memory you will need to save all data you need in onSaveInstanceState bundle   public class Fragment 1 extends Fragment         private EditText title      private Button go next        Override     public void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           setRetainInstance true     Will ignore onDestroy Method  Nested Fragments no need this if parent have it               Override     public View onCreateView LayoutInflater inflater  ViewGroup container              Bundle savedInstanceState            onRestoreInstanceStae savedInstanceState           return super onCreateView inflater  container  savedInstanceState                 Here you can restore saved data in onSaveInstanceState Bundle     private void onRestoreInstanceState Bundle savedInstanceState           if savedInstanceState  null               String SomeText   savedInstanceState getString  title                                       Here you Save your data      Override     public void onSaveInstanceState Bundle outState            super onSaveInstanceState outState           outState putString  title    Some Text

User · Answer

I m not quite sure if this question is still bothering you  since it has been several months  But I would like to share how I dealt with this  Here is the source code   int FLAG   0  private View rootView  private LinearLayout parentView          The fragment argument representing the section number for this fragment      private static final String ARG SECTION NUMBER    section number           Returns a new instance of this fragment for the given section number      public static Fragment2 newInstance Bundle bundle        Fragment2 fragment   new Fragment2        Bundle args   bundle      fragment setArguments args       return fragment     public Fragment2          Override public View onCreateView LayoutInflater inflater  ViewGroup container  Bundle savedInstanceState        super onCreateView inflater  container  savedInstanceState       Log e  onCreateView   onCreateView        if FLAG  12321           rootView   inflater inflate R layout fragment create new album  container  false           changeFLAG 12321                    parentView new LinearLayout getActivity         parentView addView rootView        return parentView         non-Javadoc      see android support v4 app Fragment onDestroy        Override public void onDestroy            TODO Auto-generated method stub     super onDestroy        Log e  onDestroy   onDestroy           non-Javadoc      see android support v4 app Fragment onStart        Override public void onStart            TODO Auto-generated method stub     super onStart        Log e  onstart   onstart           non-Javadoc      see android support v4 app Fragment onStop        Override public void onStop            TODO Auto-generated method stub     super onStop        if false           Bundle savedInstance getArguments            LinearLayout viewParent           viewParent   LinearLayout  rootView getParent            viewParent removeView rootView              parentView removeView rootView        Log e  onStop   onstop       Override public void onPause         super onPause        Log e  onpause   onpause        Override public void onResume         super onResume        Log e  onResume   onResume        And here is the MainActivity          Fragment managing the behaviors  interactions and presentation of the    navigation drawer      private NavigationDrawerFragment mNavigationDrawerFragment          Used to store the last screen title  For use in      link  restoreActionBar          public static boolean fragment2InstanceExists false  public static Fragment2 fragment2 null    Override protected void onCreate Bundle savedInstanceState        super onCreate savedInstanceState       setRequestedOrientation ActivityInfo SCREEN ORIENTATION PORTRAIT       setContentView R layout activity main        mNavigationDrawerFragment    NavigationDrawerFragment  getSupportFragmentManager                findFragmentById R id navigation drawer       mTitle   getTitle            Set up the drawer      mNavigationDrawerFragment setUp R id navigation drawer               DrawerLayout  findViewById R id drawer layout        Override public void onNavigationDrawerItemSelected int position           update the main content by replacing fragments     FragmentManager fragmentManager   getSupportFragmentManager        FragmentTransaction fragmentTransaction fragmentManager beginTransaction        switch position       case 0          fragmentTransaction addToBackStack null           fragmentTransaction replace R id container  Fragment1 newInstance position 1   commit            break      case 1           Bundle bundle new Bundle            bundle putInt  source of create  CommonMethods CREATE FROM ACTIVITY            if  fragment2InstanceExists               fragment2 Fragment2 newInstance bundle               fragment2InstanceExists true                    fragmentTransaction addToBackStack null           fragmentTransaction replace R id container  fragment2  commit             break      case 2          fragmentTransaction addToBackStack null           fragmentTransaction replace R id container  FolderExplorerFragment newInstance position 1   commit            break      default           break            The parentView is the keypoint   Normally  when onCreateView  we just use return rootView  But now  I add rootView to parentView  and then return parentView  To prevent  The specified child already has a parent  You must call removeView   on the      error  we need to call parentView removeView rootView   or the method I supplied is useless   I also would like to share how I found it  Firstly  I set up a boolean to indicate if the instance exists  When the instance exists  the rootView will not be inflated again  But then  logcat gave the child already has a parent thing  so I decided to use another parent as a intermediate Parent View  That s how it works    Hope it s helpful to you

User · Answer

Android fragment has some advantages and some disadvantages  The most disadvantage of the fragment is that when you want to use a fragment you create it ones   When you use it  onCreateView of the fragment is called for each time  If you want to keep state of the components in the fragment you must save fragment state and yout must load its state in the next shown  This make fragment view a bit slow and weird   I have found a solution and I have used this solution   Everything is great  Every body can try    When first time onCreateView is being run  create view as a global variable  When second time you call this fragment onCreateView is called again you can return this global view  The fragment component state will be kept   View view    Override public View onCreateView LayoutInflater inflater           Nullable ViewGroup container   Nullable Bundle savedInstanceState        setActionBar null       if  view    null            if   ViewGroup view getParent      null                ViewGroup view getParent    removeView view           return view             view   inflater inflate R layout mylayout  container  false

User · Answer

As stated here  Why use Fragment setRetainInstance boolean    you can also use fragments method setRetainInstance true  like this   public class MyFragment extends Fragment         Override     public void onCreate Bundle savedInstanceState            super onCreate savedInstanceState              keep the fragment and all its data across screen rotation         setRetainInstance true

User · Answer

Try this      Override protected void onPause         super onPause        if  getSupportFragmentManager   findFragmentByTag  MyFragment      null          getSupportFragmentManager   findFragmentByTag  MyFragment   setRetainInstance true       Override protected void onResume         super onResume        if  getSupportFragmentManager   findFragmentByTag  MyFragment      null          getSupportFragmentManager   findFragmentByTag  MyFragment   getRetainInstance        Hope this will help   Also you can write this to activity tag in menifest file      android configChanges  orientation screenSize    Good luck

User · Answer

In order to save the Fragment state you need to implement onSaveInstanceState     Also like an activity  you can retain the state of a fragment using a Bundle  in case the activity s process is killed and you need to restore the fragment state when the activity is recreated  You can save the state during the fragment s onSaveInstanceState   callback and restore it during either onCreate    onCreateView    or onActivityCreated    For more information about saving state  see the Activities document    http   developer android com guide components fragments html Lifecycle

User · Answer

If you using bottombar and insted of viewpager you want to set custom fragment replacement logic with retrieve previously save state you can do using below code  String current frag tag   null   String prev frag tag   null          Override     public void onTabSelected TabLayout Tab tab                 switch  tab getPosition                  case 0                   replaceFragment new Fragment1     quot Fragment1 quot                    break               case 1                  replaceFragment new Fragment2     quot Fragment2 quot                    break               case 2                  replaceFragment new Fragment3     quot Fragment3 quot                    break               case 3                 replaceFragment new Fragment4     quot Fragment4 quot                    break               default                  replaceFragment new Fragment1     quot Fragment1 quot                    break                  public void replaceFragment Fragment fragment  String tag            if  current frag tag    null                prev frag tag   current frag tag                     current frag tag   tag            FragmentManager manager   null          try               manager   requireActivity   getSupportFragmentManager                FragmentTransaction ft   manager beginTransaction                 if  manager findFragmentByTag current frag tag     null       No fragment in backStack with same tag                   ft add R id viewpagerLayout  fragment  current frag tag                    if  prev frag tag    null                        try                           ft hide Objects requireNonNull manager findFragmentByTag prev frag tag                           catch  NullPointerException e                            e printStackTrace                                                          ft show manager findFragmentByTag current frag tag                    ft addToBackStack current frag tag                   ft commit                   else                    try                       ft hide Objects requireNonNull manager findFragmentByTag prev frag tag                                 show Objects requireNonNull manager findFragmentByTag current frag tag    commit                      catch  NullPointerException e                        e printStackTrace                                              catch  Exception e                e printStackTrace                          Inside Child Fragments you can access fragment is visible or not using below method note  you have to implement below method in child fragment   Override     public void onHiddenChanged boolean hidden            super onHiddenChanged hidden            try               if hidden                   adapter getFragment mainVideoBinding viewPagerVideoMain getCurrentItem    onPause                 else                  adapter getFragment mainVideoBinding viewPagerVideoMain getCurrentItem    onResume                           catch  Exception e

[android] Android - save/restore fragment state

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