Retrieve a Fragment from a ViewPager

Question

I m using a ViewPager together with a FragmentStatePagerAdapter to host three different fragments     Fragment1   Fragment2   Fragment3    When I want to get Fragment1 from the ViewPager in the FragmentActivity    What is the problem  and how do I fix it

User · Answer

Best solution is to use the extension we created at CodePath called SmartFragmentStatePagerAdapter  Following that guide  this makes retrieving fragments and the currently selected fragment from a ViewPager significantly easier  It also does a better job of managing the memory of the fragments embedded within the adapter

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FragmentPagerAdapter is the factory of the fragments  To find a fragment based on its position if still in memory use this   public Fragment findFragmentByPosition int position        FragmentPagerAdapter fragmentPagerAdapter   getFragmentPagerAdapter        return getSupportFragmentManager   findFragmentByTag               android switcher     getViewPager   getId                               fragmentPagerAdapter getItemId position        Sample code for v4 support api

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In Fragment  public int getArgument       return mPage    public void update         In FragmentActivity  List lt Fragment gt  fragments   getSupportFragmentManager   getFragments    for Fragment f fragments       if  f instanceof PageFragment  amp  amp   f isDetached                PageFragment pf    PageFragment f               if pf getArgument    pager getCurrentItem   pf update

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In order to get current Visible fragment from ViewPager  I am using this simple statement and it s working fine          public Fragment getFragmentFromViewpager                      return   Fragment   mAdapter instantiateItem mViewPager  mViewPager getCurrentItem

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Fragment yourFragment   yourviewpageradapter getItem int index     index is the place of fragment in adapter like you added fragment1 first so retreive fragment1 pass index as 0 and so on for rest

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I implemented this easy with a bit different approach   My custom FragmentAdapter getItem method returned not new MyFragment    but the instance of MyFragment that was created in FragmentAdapter constructor    In my activity I then got the fragment from the adapter  check if it is instanceOf needed Fragment  then cast and use needed methods

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The main answer relies on a name being generated by the framework  If that ever changes  then it will no longer work   What about this solution  overriding instantiateItem   and destroyItem   of your Fragment State PagerAdapter   public class MyPagerAdapter extends FragmentStatePagerAdapter       SparseArray lt Fragment gt  registeredFragments   new SparseArray lt Fragment gt          public MyPagerAdapter FragmentManager fm            super fm               Override     public int getCount             return                  Override     public Fragment getItem int position            return MyFragment newInstance                    Override     public Object instantiateItem ViewGroup container  int position            Fragment fragment    Fragment  super instantiateItem container  position           registeredFragments put position  fragment           return fragment              Override     public void destroyItem ViewGroup container  int position  Object object            registeredFragments remove position           super destroyItem container  position  object              public Fragment getRegisteredFragment int position            return registeredFragments get position             This seems to work for me when dealing with Fragments that are available  Fragments that have not yet been instantiated  will return null when calling getRegisteredFragment  But I ve been using this mostly to get the current Fragment out of the ViewPager  adapater getRegisteredFragment viewPager getCurrentItem    and this won t return null   I m not aware of any other drawbacks of this solution  If there are any  I d like to know

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I know this has a few answers  but maybe this will help someone  I have used a relatively simple solution when I needed to get a Fragment from my ViewPager  In your Activity or Fragment holding the ViewPager  you can use this code to cycle through every Fragment it holds    FragmentPagerAdapter fragmentPagerAdapter    FragmentPagerAdapter  mViewPager getAdapter    for int i   0  i  lt  fragmentPagerAdapter getCount    i          Fragment viewPagerFragment   fragmentPagerAdapter getItem i       if viewPagerFragment    null               Do something with your Fragment            Check viewPagerFragment isResumed   if you intend on interacting with any views             If you know the position of your Fragment in the ViewPager  you can just call getItem knownPosition   If you don t know the position of your Fragment in the ViewPager  you can have your children Fragments implement an interface with a method like getUniqueId    and use that to differentiate them  Or you can cycle through all Fragments and check the class type  such as if viewPagerFragment instanceof FragmentClassYouWant        EDIT      I have discovered that getItem only gets called by a FragmentPagerAdapter when each Fragment needs to be created the first time  after that  it appears the the Fragments are recycled using the FragmentManager  This way  many implementations of FragmentPagerAdapter create new Fragments in getItem  Using my above method  this means we will create new Fragments each time getItem is called as we go through all the items in the FragmentPagerAdapter  Due to this  I have found a better approach  using the FragmentManager to get each Fragment instead  using the accepted answer   This is a more complete solution  and has been working well for me   FragmentPagerAdapter fragmentPagerAdapter    FragmentPagerAdapter  mViewPager getAdapter    for int i   0  i  lt  fragmentPagerAdapter getCount    i          String name   makeFragmentName mViewPager getId    i       Fragment viewPagerFragment   getChildFragmentManager   findFragmentByTag name          OR Fragment viewPagerFragment   getFragmentManager   findFragmentByTag name       if viewPagerFragment    null                Do something with your Fragment         if  viewPagerFragment isResumed                     Interact with any views data that must be alive                   else                  Flag something for update later  when this viewPagerFragment                returns to onResume                     And you will need this method   private static String makeFragmentName int viewId  int position        return  android switcher     viewId         position

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You don t need to call getItem   or some other method at later stage to get the reference of a Fragment hosted inside ViewPager  If you want to update some data inside Fragment then use this approach  Update ViewPager dynamically   Key is to set new data inside Adaper and call notifyDataSetChanged   which in turn will call getItemPosition    passing you a reference of your Fragment and giving you a chance to update it  All other ways require you to keep reference to yourself or some other hack which is not a good solution    Override public int getItemPosition Object object        if  object instanceof UpdateableFragment              UpdateableFragment  object  update xyzData               don t return POSITION NONE  avoid fragment recreation       return super getItemPosition object

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For my case  none of the above solutions worked   However since I am using the Child Fragment Manager in a Fragment  the following was used   Fragment f   getChildFragmentManager   getFragments   get viewPager getCurrentItem      This will only work if your fragments in the Manager correspond to the viewpager item

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I handled it by first making a list of all the fragments  List lt Fragment gt  fragments   that I was going to use then added them to the pager making it easier to handle the currently viewed fragment   So    Override onCreate          initialise the list of fragments     fragments   new Vector lt Fragment gt            fill up the list with out fragments     fragments add Fragment instantiate this  MainFragment class getName          fragments add Fragment instantiate this  MenuFragment class getName          fragments add Fragment instantiate this  StoresFragment class getName          fragments add Fragment instantiate this  AboutFragment class getName          fragments add Fragment instantiate this  ContactFragment class getName              Set up the pager     pager    ViewPager findViewById R id pager       pager setAdapter new MyFragmentPagerAdapter getSupportFragmentManager    fragments        pager setOffscreenPageLimit 4       so then this can be called   public Fragment getFragment ViewPager pager          Fragment theFragment   fragments get pager getCurrentItem         return theFragment      so then i could chuck it in an if statement that would only run if it was on the correct fragment  Fragment tempFragment   getFragment    if tempFragment    MyFragmentNo2 class       MyFragmentNo2 theFrag    MyFragmentNo2  tempFragment        then you can do whatever with the fragment     theFrag costomFunction        but thats just my hack and slash approach but it worked for me  I use it do do relevent changes to my currently displayed fragment when the back button is pushed

User · Answer

Easy way to iterate over fragments in fragment manager  Find viewpager  that has section position argument  placed in  public static PlaceholderFragment newInstance int sectionNumber    public PlaceholderFragment getFragmentByPosition Integer pos       for Fragment f getChildFragmentManager   getFragments             if f getId    R id viewpager  amp  amp  f getArguments   getInt  SECTNUM   - 1    pos                return  PlaceholderFragment  f                      return null

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Must extends FragmentPagerAdapter into your ViewPager adapter class  If you use FragmentStatePagerAdapter then you will not able to find your Fragment by its ID  public static String makeFragmentName int viewPagerId  int index      return  android switcher     viewPagerId         index      How to use this method  -  Fragment mFragment     FragmentActivity  getContext    getSupportFragmentManager   findFragmentByTag         AppMethodUtils makeFragmentName mViewPager getId    i     InterestViewFragment newFragment    InterestViewFragment  mFragment

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in TabLayout there are multiple tab for Fragment  you can find the fragment by Tag using the index of the fragment   For ex  the index for Fragment1 is 0  so in findFragmentByTag   method  pass the tag for the Viewpager after using fragmentTransaction you can add replace the fragment   String tag    android switcher     R id viewPager         0   Fragment1 f    Fragment1  getSupportFragmentManager   findFragmentByTag tag

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Create integer resource id in  values integers xml   lt integer name  page1  gt 1 lt  integer gt   lt integer name  page2  gt 2 lt  integer gt   lt integer name  page3  gt 3 lt  integer gt    Then in PagerAdapter getItem function   public Fragment getItem int position             Fragment fragment   null           if  position    0                fragment   FragmentOne newInstance                mViewPager setTag R integer page1 fragment                      else if  position    1                 fragment   FragmentTwo newInstance                mViewPager setTag R integer page2 fragment              else if  position    2                 fragment   FragmentThree newInstance                mViewPager setTag R integer page3 fragment                       return fragment              Then in activity write this function to get fragment reference   private Fragment getFragmentByPosition int position        Fragment fragment   null       switch  position            case 0              fragment    Fragment  mViewPager getTag R integer page1               break           case 1               fragment    Fragment  mViewPager getTag R integer page2               break           case 2              fragment    Fragment  mViewPager getTag R integer page3               break                             return fragment          Get the fragment reference by calling the above function and then cast it to your custom fragment   Fragment fragment   getFragmentByPosition position            if  fragment    null                        FragmentOne fragmentOne    FragmentOne  fragment

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For grabbing fragments out of a ViewPager there are a lot of answers on here and on other related SO threads   blogs  Everyone I have seen is broken  and they generally seem to fall into one of the two types listed below  There are some other valid solutions if you only want to grab the current fragment  like this other answer on this thread   If using FragmentPagerAdapter see below  If using FragmentStatePagerAdapter its worth looking at this  Grabbing indexes that are not the current one in a FragmentStateAdapter is not as useful as by the nature of it these will be completely torn down went out of view   out of offScreenLimit bounds   THE UNHAPPY PATHS  Wrong  Maintain your own internal list of fragments  added to when FragmentPagerAdapter getItem   is called   Usually using a SparseArray or Map Not one of the many examples I have seen accounts for lifecycle events so this solution is fragile  As getItem is only called the first time a page is scrolled to  or obtained if your ViewPager setOffscreenPageLimit x    0  in the ViewPager  if the hosting Activity   Fragment is killed or restarted then the internal SpaseArray will be wiped out when the custom FragmentPagerActivity is recreated  but behind the scenes the ViewPagers internal fragments will be recreated  and getItem will NOT be called for any of the indexes  so the ability to get a fragment from index will be lost forever  You can account for this by saving out and restoring these fragment references via FragmentManager getFragment   and  putFragment but this starts to get messy IMHO    Wrong  Construct your own tag id matching what is used under the hood in FragmentPagerAdapter and use this to retrieve the page Fragments from the FragmentManager   This is better insomuch as it copes with the losing-fragment-references problem in the first internal-array solution  but as rightly pointed out in the answers above and elsewhere on the net - it feels hacky as its a private method internal to ViewPager that could change at any time or for any OS version    The method thats recreated for this solution is   private static String makeFragmentName int viewId  long id        return  android switcher     viewId         id      A HAPPY PATH  ViewPager instantiateItem    A similar approach to getItem   above but non-lifecycle-breaking is to this is to hook into instantiateItem   instead of getItem   as the former will be called everytime that index is created   accessed  See this answer  A HAPPY PATH  Construct your own FragmentViewPager  Construct your own FragmentViewPager class from the source of the latest support lib and change the method used internally to generate the fragment tags  You can replace it with the below  This has the advantage that you know the tag creation will never change and your not relying on a private api   method  which is always dangerous           param containerViewId the ViewPager this adapter is being supplied to     param id pass in getItemId position  as this is whats used internally in this class     return the tag used for this pages fragment     public static String makeFragmentName int containerViewId  long id        return  android switcher     containerViewId         id      Then as the doc says  when you want to grab a fragment used for an index just call something like this method  which you can put in the custom FragmentPagerAdapter or a subclass  being aware the result may be null if getItem has not yet been called for that page i e  its not been created yet           return may return null if the fragment has not been instantiated yet for that position - this depends on if the fragment has been viewed    yet OR is a sibling covered by   link android support v4 view ViewPager setOffscreenPageLimit int    Can use this to call methods on    the current positions fragment      public  Nullable Fragment getFragmentForPosition int position        String tag   makeFragmentName mViewPager getId    getItemId position        Fragment fragment   getSupportFragmentManager   findFragmentByTag tag       return fragment      This is a simple solution and solves the issues in the other two solutions found everywhere on the web

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Another simple solution       public class MyPagerAdapter extends FragmentPagerAdapter           private Fragment mCurrentFragment           public Fragment getCurrentFragment                 return mCurrentFragment                               Override         public void setPrimaryItem ViewGroup container  int position  Object object                if  getCurrentFragment      object                    mCurrentFragment     Fragment  object                             super setPrimaryItem container  position  object

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Hey I have answered this question here  Basically  you need to override      public Object instantiateItem ViewGroup container  int position    method of FragmentStatePagerAdapter

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This is based on Steven s answer above  This will return actual instance of the fragment which is already attached to the parent activity                       FragmentPagerAdapter fragmentPagerAdapter    FragmentPagerAdapter  mViewPager getAdapter        for int i   0  i  lt  fragmentPagerAdapter getCount    i               Fragment viewPagerFragment    Fragment  mViewPager getAdapter   instantiateItem mViewPager  i           if viewPagerFragment    null  amp  amp  viewPagerFragment isAdded                   if  viewPagerFragment instanceof FragmentOne                   FragmentOne oneFragment    FragmentOne  viewPagerFragment                  if  oneFragment    null                       oneFragment update       your custom method                                 else if  viewPagerFragment instanceof FragmentTwo                   FragmentTwo twoFragment    FragmentTwo  viewPagerFragment                   if  twoFragment    null                       twoFragment update       your custom method

User · Answer

I couldn t find a simple  clean way to do this  However  the ViewPager widget is just another ViewGroup   which hosts your fragments  The ViewPager has these fragments as immediate children  So you could just iterate over them  using  getChildCount   and  getChildAt      and see if the fragment instance that you re looking for is currently loaded into the ViewPager and get a reference to it  E g  you could use some static unique ID field to tell the fragments apart   Note that the ViewPager may not have loaded the fragment you re looking for since it s a virtualizing container like ListView

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Ok for the adapter FragmentStatePagerAdapter I fund a solution    in your FragmentActivity    ActionBar mActionBar   getSupportActionBar     mActionBar addTab mActionBar newTab   setText  TAB1   setTabListener this  setTag Fragment instantiate this  MyFragment1 class getName       mActionBar addTab mActionBar newTab   setText  TAB2   setTabListener this  setTag Fragment instantiate this  MyFragment2 class getName       mActionBar addTab mActionBar newTab   setText  TAB3   setTabListener this  setTag Fragment instantiate this  MyFragment3 class getName        viewPager    STViewPager  super findViewById R id viewpager   mPagerAdapter   new MyPagerAdapter getSupportFragmentManager    mActionBar   viewPager setAdapter this mPagerAdapter     and create a methode in your class FragmentActivity - So that method give you access to your Fragment  you just need to give it the position of the fragment you want   public Fragment getActiveFragment int position    String name   MyPagerAdapter makeFragmentName position   return getSupportFragmentManager   findFragmentByTag name       in your Adapter     public class MyPagerAdapter extends FragmentStatePagerAdapter    private final ActionBar actionBar  private final FragmentManager fragmentManager   public MyPagerAdapter FragmentManager fragmentManager  com actionbarsherlock app ActionBarActionBar mActionBar   super fragmentManager   this actionBar   mActionBar  this fragmentManager   fragmentManager      Override public Fragment getItem int position    getSupportFragmentManager   beginTransaction   add mTchatDetailsFragment  makeFragmentName position   commit    return  Fragment this actionBar getTabAt position       Override public int getCount     return this actionBar getTabCount        Override public CharSequence getPageTitle int position    return this actionBar getTabAt position  getText       private static String makeFragmentName int viewId  int index    return  android fragment     index

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The easiest and the most concise way  If all your fragments in ViewPager are of different classes you may retrieve and distinguish them as following   public class MyActivity extends Activity         Override     public void onAttachFragment Fragment fragment            super onAttachFragment fragment           if  fragment getClass      MyFragment class                mMyFragment    MyFragment  fragment

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Add next methods to your FragmentPagerAdapter   public Fragment getActiveFragment ViewPager container  int position    String name   makeFragmentName container getId    position   return  mFragmentManager findFragmentByTag name      private static String makeFragmentName int viewId  int index        return  android switcher     viewId         index      getActiveFragment 0  has to work    Here is the solution implemented into ViewPager https   gist github com jacek-marchwicki d6320ba9a910c514424d  If something fail you will see good crash log

[android] Retrieve a Fragment from a ViewPager

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