Getting the current Fragment instance in the viewpager

Question

Below is my code which has 3 Fragment classes each embedded with each of the 3 tabs on ViewPager  I have a menu option  As shown in the onOptionsItemSelected    by selecting an option  I need to update the fragment that is currently visible  To update that I have to call a method which is in the fragment class  Can someone please suggest how to call that method   public class MainActivity  extends ActionBarActivity         ViewPager ViewPager       TabsAdapter TabsAdapter         Override         public void onCreate Bundle savedInstanceState                super onCreate savedInstanceState                ViewPager   new ViewPager this               ViewPager setId R id pager               setContentView ViewPager                final ActionBar bar   getSupportActionBar                 bar setNavigationMode ActionBar NAVIGATION MODE TABS                  Attaching the Tabs to the fragment classes and setting the tab title              TabsAdapter   new TabsAdapter this  ViewPager               TabsAdapter addTab bar newTab   setText  FragmentClass1                        FragmentClass1 class  null               TabsAdapter addTab bar newTab   setText  FragmentClass2                  FragmentClass2 class  null               TabsAdapter addTab bar newTab   setText  FragmentClass3                  FragmentClass3 class  null                 if  savedInstanceState    null                    bar setSelectedNavigationItem savedInstanceState getInt  tab   0                                       Override         public boolean onOptionsItemSelected MenuItem item                 switch  item getItemId                   case R id addText                   Here I need to call the method which exists in the currently visible Fragment class                        return true                              return super onOptionsItemSelected item                     Override      protected void onSaveInstanceState Bundle outState          super onSaveInstanceState outState               outState putInt  tab   getSupportActionBar   getSelectedNavigationIndex                   public static class TabsAdapter extends FragmentPagerAdapter       implements ActionBar TabListener  ViewPager OnPageChangeListener          private final Context mContext              private final ActionBar mActionBar              private final ViewPager mViewPager              private final ArrayList lt TabInfo gt  mTabs   new ArrayList lt TabInfo gt                  static final class TabInfo                   private final Class lt   gt  clss                  private final Bundle args                   TabInfo Class lt   gt   class  Bundle  args                        clss    class                      args    args                                         public TabsAdapter ActionBarActivity activity  ViewPager pager           super activity getSupportFragmentManager                     mContext   activity                  mActionBar   activity getSupportActionBar                    mViewPager   pager                  mViewPager setAdapter this                   mViewPager setOnPageChangeListener this                        public void addTab ActionBar Tab tab  Class lt   gt  clss  Bundle args                    TabInfo info   new TabInfo clss  args                   tab setTag info                   tab setTabListener this                   mTabs add info                   mActionBar addTab tab                   notifyDataSetChanged                           Override       public void onPageScrollStateChanged int state              TODO Auto-generated method stub                  Override       public void onPageScrolled int position  float positionOffset  int positionOffsetPixels              TODO Auto-generated method stub                  Override       public void onPageSelected int position              TODO Auto-generated method stub        mActionBar setSelectedNavigationItem position                   Override       public void onTabReselected Tab tab  FragmentTransaction ft              TODO Auto-generated method stub                  Override       public void onTabSelected Tab tab  FragmentTransaction ft           Object tag   tab getTag                    for  int i 0  i lt mTabs size    i                          if  mTabs get i     tag                            mViewPager setCurrentItem i                                                             tabPosition   tab getPosition                    Override       public void onTabUnselected Tab tab  FragmentTransaction ft              TODO Auto-generated method stub                  Override       public Fragment getItem int position           TabInfo info   mTabs get position                   return Fragment instantiate mContext  info clss getName    info args                   Override       public int getCount            return mTabs size                             Suppose below is the fragment class with the method updateList   I want to call    public class FragmentClass1       ArrayList lt String gt  originalData         Override          public View onCreateView LayoutInflater inflater  ViewGroup container             Bundle savedInstanceState               View fragmentView   inflater inflate R layout frag1  container  false              originalData   getOriginalDataFromDB               return fragmentView                    public void updateList String text               originalData add text            Here I could do other UI part that need to added

User · Answer

Best way to do this  just call CallingFragmentName fragment    CallingFragmentName  viewPager  getAdapter    instantiateItem viewPager  viewPager getCurrentItem     It will re-instantiate your calling Fragment  so that it will not throw null pointer exception and call any method of that fragment

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FragmentStatePagerAdapter has public method with the name instantiateItem that return your fragment based on specified parameter values  this method has two parameters ViewGroup  ViewPager  and position   public Object instantiateItem ViewGroup container  int position     Used this method to get specified position s fragment   Fragment fragment    Fragment  adaper instantiateItem mViewPager  position

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In my Activity I have   int currentPage   0   start at the first tab private SparseArray lt Fragment gt  fragments   list off fragments viewPager setOnPageChangeListener new OnPageChangeListener       Override public void onPageSelected int pos            currentPage   pos   update current page     Override public void onPageScrolled int arg0  float arg1  int arg2      Override public void onPageScrollStateChanged int arg0             Override public void onAttachFragment Fragment fragment        super onAttachFragment fragment       if fragment instanceof Fragment1          fragments put 0  fragment       if fragment instanceof Fragment2          fragments put 2  fragment       if fragment instanceof Fragment3          fragments put 3  fragment       if fragment instanceof Fragment4          fragments put 4  fragment      Then I have the following method for getting the current fragment  public Fragment getCurrentFragment         return fragments get currentPage

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You can define the PagerAdapter like this then you will able to get any Fragment in ViewPager   private class PagerAdapter extends FragmentPagerAdapter       private final List lt Fragment gt  mFragmentList   new ArrayList lt  gt          public PagerAdapter FragmentManager fm            super fm               Override     public Fragment getItem int position            return mFragmentList get position               Override     public int getCount             return mFragmentList size               public void addFragment Fragment fragment            mFragmentList add fragment             To get the current Fragment  Fragment currentFragment   mPagerAdapter getItem mViewPager getCurrentItem

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After reading all comments and answers I am going to explain an optimal solution for this problem  The best option is  rik s solution  so my improvement is base on his    Instead of having to ask each FragmentClass like  if FragmentClass1          if FragmentClass2              Create your own interface  and maker your child fragments implement it  something like  public interface MyChildFragment       void updateView int position       Then  you can do something like this to initiate and update your inner fragments   Fragment childFragment    Fragment  mViewPagerDetailsAdapter instantiateItem mViewPager mViewPager getCurrentItem      if  childFragment    null         MyChildFragment  childFragment  updateView        P S  Be careful where you put that code  if you call insatiateItem before the system actually create it the savedInstanceState of your child fragment will be null therefor  public void onCreate  Nullable Bundle savedInstanceState         super savedInstanceState      Will crash your app   Good luck

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This is the simplest hack   fun getCurrentFragment    Fragment        return if  count    0  null     else instantiateItem view pager  view pager currentItem  as  Fragment      kotlin code   Just call instantiateItem viewPager  viewPager getCurrentItem   and cast it to Fragment  Your item would already be instantiated  To be sure you can add a check for getCount   Works with both FragmentPagerAdapter and FragmentStatePagerAdapter

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I know its too late but I have really simple ways of doing it      for fragment at 0 possition    mFragment  viewPager getAdapter   instantiateItem viewPager  0   yourMethod

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First of all keep track of all the  active  fragment pages  In this case  you keep track of the fragment pages in the FragmentStatePagerAdapter  which is used by the ViewPager    Override public Fragment getItem int index        Fragment myFragment   MyFragment newInstance        mPageReferenceMap put index  myFragment       return myFragment      To avoid keeping a reference to  inactive  fragment pages  you need to implement the FragmentStatePagerAdapter s destroyItem      method    Override public void destroyItem  ViewGroup container  int position  Object object        super destroyItem container  position  object       mPageReferenceMap remove position       and when you need to access the currently visible page  you then call   int index   mViewPager getCurrentItem    MyAdapter adapter     MyAdapter mViewPager getAdapter     MyFragment fragment   adapter getFragment index     Where the MyAdapter s getFragment int  method looks like this   public MyFragment getFragment int key        return mPageReferenceMap get key       Hope it may help

User · Answer

getSupportFragmentManager   getFragments   get viewPager getCurrentItem       Cast the instance retreived from above line to the fragment you want to work on with  Works perfectly fine   viewPager   is the pager instance managing the fragments

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by selecting an option  I need to update the fragment that is   currently visible    A simple way of doing this is using a trick related to the FragmentPagerAdapter implementation   case R id addText       Fragment page   getSupportFragmentManager   findFragmentByTag  android switcher     R id pager         ViewPager getCurrentItem             based on the current position you can then cast the page to the correct          class and call the method       if  ViewPager getCurrentItem      0  amp  amp  page    null                FragmentClass1 page  updateList  new item                 return true    Please rethink your variable naming convention  using as the variable name the name of the class is very confusing so no ViewPager ViewPager  use ViewPager mPager for example

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Override setPrimaryItem from your FragmentPagerAdapter  the object is the visible fragment     Override         public void setPrimaryItem ViewGroup container  int position  Object object                if  mCurrentFragment    object                    mCurrentFragment    LeggiCapitoloFragment  object                            super setPrimaryItem container  position  object

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Simply get the current item from pager and then ask your adapter to the fragment of that position    int currentItem   viewPager getCurrentItem        Fragment item   mPagerAdapter getItem currentItem       if  null    item  amp  amp  item isVisible               do whatever want to do with fragment after doing type checking         return

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If your pager is inside a Fragment then use this   private fun getPagerCurrentFragment    Fragment        return childFragmentManager findFragmentByTag  android switcher   R id myViewPagerId    myViewPager currentItem        Where R id myViewPagerId is the id of your ViewPager inside the xml Layout

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In my previous implementation I stored a list of child Fragments to be able to access them later  but this turned out to be a wrong implementation causing huge memory leaks   I end up using instantiateItem      method to get current Fragment   val currentFragment   adapter  instantiateItem viewPager  viewPager currentItem    Or to get any other Fragment on position   val position   0 val myFirstFragment  MyFragment     adapter  instantiateItem viewPager  position  as  MyFragment    From documentation      Create the page for the given position  The adapter is responsible for   adding the view to the container given here  although it only must   ensure this is done by the time it returns from   finishUpdate ViewGroup

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You can declare an Array of fragment as register fragments  class DashboardPagerAdapter fm  FragmentManager     FragmentStatePagerAdapter fm             CURRENT FRAGMENT     val registeredFragments   SparseArray lt Fragment gt         override fun instantiateItem container  ViewGroup  position  Int   Any           val fragment   super instantiateItem container  position  as Fragment         registeredFragments put position  fragment          return fragment            override fun getItem position  Int   Fragment           return when  position                0 - gt  HomeFragment newInstance               1 - gt  ConverterDashboardFragment newInstance               2 - gt  CartFragment newInstance               3 - gt  CustomerSupportFragment newInstance               4 - gt  ProfileFragment newInstance               else - gt  ProfileFragment newInstance                        override fun getCount    Int           return 5            Then you can use it as  adapter  let       val cartFragment   it registeredFragments 2  as CartFragment      cartFragment  myCartApi true

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I tried the following   int index   mViewPager getCurrentItem     List lt Fragment gt  fragments   getSupportFragmentManager   getFragments     View rootView   fragments get index  getView

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The scenario in question is better served by each Fragment adding its own menu items and directly handling onOptionsItemSelected    as described in official documentation   It is better to avoid undocumented tricks

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You can implement a BroadcastReceiver in the Fragment and send an Intent from anywhere   The fragment s receiver can listen for the specific action and invoke the instance s method   One caveat is making sure the View component is already instantiated and  and for some operations  such as scrolling a list  the ListView  must already be rendered

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Based on what he answered  chahat jain     When we use the viewPager  a good way to access the fragment instance in activity is instantiateItem viewpager index     index- index of fragment of which you want instance    If you want to do that in kotlin   val fragment    mv viewpager adapter   instantiateItem mv viewpager  0  as Fragment                 if   fragment is YourFragmentFragment                                           DO somthign                       0 to the fragment instance of 0                                                                                                               Example of uses                                                                                                                    Here is a complete example to get a losest vision about   here is  my veiewPager in the  xml file              lt android support v4 view ViewPager                 android id    id mv viewpager                  android layout width  match parent                  android layout height  match parent                  android layout margin  5dp   gt            And the home activity where i insert the tab       import kotlinx android synthetic main movie tab    class HomeActivity   AppCompatActivity          lateinit var  adapter HomeTabPagerAdapter      override fun onCreate savedInstanceState  Bundle                             override fun onCreateOptionsMenu menu  Menu   Boolean                           mSearchView setOnQueryTextListener object   SearchView OnQueryTextListener                              override fun onQueryTextChange newText  String   Boolean                    if  mv viewpager currentItem    0                                        val fragment    mv viewpager adapter   instantiateItem mv viewpager  0  as Fragment                     if   fragment is ListMoviesFragment                          fragment onQueryTextChange newText                                    else                                       val fragment    mv viewpager adapter   instantiateItem mv viewpager  1  as Fragment                     if   fragment is ListShowFragment                          fragment onQueryTextChange newText                                    return true                                  return super onCreateOptionsMenu menu

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by selecting an option  I need to update the fragment that is currently visible    To get a reference to currently visible fragment  assume you have a reference to ViewPager as mPager  Then following steps will get a reference to currentFragment    PageAdapter adapter   mPager getAdapter    int fragmentIndex   mPager getCurrentItem    FragmentStatePagerAdapter fspa    FragmentStatePagerAdapter adapter  Fragment currentFragment   fspa getItem fragmentIndex     The only cast used line 3 is valid usually  FragmentStatePagerAdapter is an useful adapter for a ViewPager

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This is the only way I don t get NullPointerException for the instance variables of that particular fragment classes  This might be helpful for others who stuck at the same thing  In the onOptionsItemSelected    I coded the below way   if viewPager getCurrentItem      0        FragmentClass1 frag1    FragmentClass1 viewPager                              getAdapter                                instantiateItem viewPager  viewPager getCurrentItem         frag1 updateList text      else if viewPager getCurrentItem      1        FragmentClass2 frag2    FragRecentApps viewPager                              getAdapter                                instantiateItem viewPager  viewPager getCurrentItem         frag2 updateList text

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This is more future-proof than the accepted answer   public class MyFragmentPagerAdapter extends FragmentPagerAdapter           ------------------------------------------------------------------------------------------           region Private attributes        private Context  context      private FragmentManager  fragmentManager      private Map lt Integer  String gt   fragmentsTags   new HashMap lt  gt             endregion        ------------------------------------------------------------------------------------------              ------------------------------------------------------------------------------------------           region Constructor        public MyFragmentPagerAdapter Context context  FragmentManager fragmentManager             super fragmentManager             context   context           fragmentManager   fragmentManager                endregion        ------------------------------------------------------------------------------------------              ------------------------------------------------------------------------------------------           region FragmentPagerAdapter methods         Override     public int getCount     return 2          Override     public Fragment getItem int position             if  fragmentsTags containsKey position                  return  fragmentManager findFragmentByTag  fragmentsTags get position                      else                switch  position                     case 0     return Fragment instantiate  context  Tab1Fragment class getName                       case 1     return Fragment instantiate  context  Tab2Fragment class getName                                        return null              Override     public Object instantiateItem ViewGroup container  int position                Instantiate the fragment and get its tag           Fragment result    Fragment  super instantiateItem container  position            fragmentsTags put position  result getTag              return result                endregion        ------------------------------------------------------------------------------------------

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When we use the viewPager  a good way to access the fragment instance in activity is instantiateItem viewpager index     index- index of fragment of which you want instance   for example I am accessing the fragment instance of 1 index-   Fragment fragment    Fragment  viewPageradapter instantiateItem viewPager  1    if  fragment    null  amp  amp  fragment instanceof MyFragment             MyFragment  fragment  callYourFunction

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I had the same issue and solved it using this code   MyFragment fragment    MyFragment  thisActivity getFragmentManager   findFragmentById R id container     Just replace the name MyFragment with the name of your fragment and add the id of your fragment container

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I have used the following    int index   vpPager getCurrentItem     MyPagerAdapter adapter     MyPagerAdapter vpPager getAdapter      MyFragment suraVersesFragment    MyFragment adapter getRegisteredFragment index

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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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Current Fragment   This works if you created a project with the fragments tabbar template   Fragment f   mSectionsPagerAdapter getItem mViewPager getCurrentItem       Note that this works with the default tabbed activity template implementation

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There are a lot of answers here that don t really address the basic fact that there s really NO WAY to do this predictably  and in a way that doesn t result you shooting yourself in the foot at some point in the future   FragmentStatePagerAdapter is the only class that knows how to reliably access the fragments that are tracked by the FragmentManager - any attempt to try and guess the fragment s id or tag is not reliable  long-term  And attempts to track the instances manually will likely not work well when state is saved restored  because FragmentStatePagerAdapter may well not call the callbacks when it restores the state   About the only thing that I ve been able to make work is copying the code for FragmentStatePagerAdapter and adding a method that returns the fragment  given a position  mFragments get pos    Note that this method assumes that the fragment is actually available  i e  it was visible at some point    If you re particularly adventurous  you can use reflection to access the elements of the private mFragments list  but then we re back to square one  the name of the list is not guaranteed to stay the same

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To get current fragment - get position in ViewPager at public void onPageSelected final int position   and then  public PlaceholderFragment getFragmentByPosition Integer pos       for Fragment f getChildFragmentManager   getFragments             if f getId    R viewpager  amp  amp  f getArguments   getInt  SECTNUM   - 1    pos                return  PlaceholderFragment  f                      return null      SECTNUM - position argument assigned in public static PlaceholderFragment newInstance int sectionNumber   of Fragment  getChildFragmentManager   or getFragmentManager   - depends on how created SectionsPagerAdapter

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FragmentStatePagerAdapter has a private instance variable called mCurrentPrimaryItem of type Fragment  One can only wonder why Android devs did not supplied it with a getter  This variable is instantiated in setPrimaryItem   method  So  override this method in such a way for you to get the reference to this variable  I simply ended up with declaring my own mCurrentPrimaryItem and copying the contents of setPrimaryItem   to my override   In your implementation of FragmentStatePagerAdapter   private Fragment mCurrentPrimaryItem   null    Override public void setPrimaryItem ViewGroup container  int position  Object object        Fragment fragment    Fragment object      if  fragment    mCurrentPrimaryItem            if  mCurrentPrimaryItem    null                mCurrentPrimaryItem setMenuVisibility false               mCurrentPrimaryItem setUserVisibleHint false                     if  fragment    null                fragment setMenuVisibility true               fragment setUserVisibleHint true                     mCurrentPrimaryItem   fragment           public TasksListFragment getCurrentFragment         return  YourFragment  mCurrentPrimaryItem

[android] Getting the current Fragment instance in the viewpager

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