Callback to a Fragment from a DialogFragment

Question

Question  How does one create a callback from a DialogFragment to another Fragment   In my case  the Activity involved should be completely unaware of the DialogFragment   Consider I have  public class MyFragment extends Fragment implements OnClickListener   Then at some point I could do  DialogFragment dialogFrag   MyDialogFragment newInstance this   dialogFrag show getFragmentManager  null     Where MyDialogFragment looks like   protected OnClickListener listener  public static DialogFragment newInstance OnClickListener listener        DialogFragment fragment   new DialogFragment        fragment listener   listener      return fragment      But there is no guarantee that the listener will be around if the DialogFragment pauses and resumes through its lifecycle   The only guarantees in a Fragment are those passed in through a Bundle via setArguments and getArguments   There is a way to reference the activity if it should be the listener   public Dialog onCreateDialog Bundle bundle        OnClickListener listener    OnClickListener  getActivity                 return new AlertDialog Builder getActivity                              setAdapter adapter  listener           create        But I don t want the Activity to listen for events  I need a Fragment   Really  it could be any Java object that implements OnClickListener   Consider the concrete example of a Fragment that presents an AlertDialog via DialogFragment   It has Yes No buttons   How can I send these button presses back to the Fragment that created it

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According to the official documentation   Fragment setTargetFragment     Optional target for this fragment  This may be used  for example  if this fragment is being started by another  and when done wants to give a result back to the first  The target set here is retained across instances via FragmentManager putFragment    Fragment getTargetFragment     Return the target fragment set by setTargetFragment Fragment  int     So you can do this      In your fragment  public class MyFragment extends Fragment implements OnClickListener       private void showDialog             DialogFragment dialogFrag   MyDialogFragment newInstance this              Add this         dialogFrag setTargetFragment this  0           dialogFrag show getFragmentManager  null                       then  public class MyialogFragment extends DialogFragment        Override     public void onAttach Context context            super onAttach context              Then get it         Fragment fragment   getTargetFragment            if  fragment instanceof OnClickListener                listener    OnClickListener  fragment            else               throw new RuntimeException  you must implement OnClickListener

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I solved this in an elegant way with RxAndroid  Receive an observer in the constructor of the DialogFragment and suscribe to observable and push the value when the callback being called  Then  in your Fragment create an inner class of the Observer  create an instance and pass it in the constructor of the DialogFragment  I used WeakReference in the observer to avoid memory leaks  Here is the code   BaseDialogFragment java  import java lang ref WeakReference   import io reactivex Observer   public class BaseDialogFragment lt O gt  extends DialogFragment        protected WeakReference lt Observer lt O gt  gt  observerRef       protected BaseDialogFragment Observer lt O gt  observer            this observerRef   new WeakReference lt  gt  observer             protected Observer lt O gt  getObserver         return observerRef get              DatePickerFragment java  public class DatePickerFragment extends BaseDialogFragment lt Integer gt      implements DatePickerDialog OnDateSetListener     public DatePickerFragment Observer lt Integer gt  observer        super observer       Override public Dialog onCreateDialog Bundle savedInstanceState           Use the current date as the default date in the picker     final Calendar c   Calendar getInstance        int year   c get Calendar YEAR       int month   c get Calendar MONTH       int day   c get Calendar DAY OF MONTH           Create a new instance of DatePickerDialog and return it     return new DatePickerDialog getActivity    this  year  month  day       Override public void onDateSet DatePicker view  int year  int month  int dayOfMonth            if  getObserver      null                Observable just month  subscribe getObserver                         MyFragment java    Show the dialog fragment when the button is clicked  OnClick R id btn date  void onDateClick         DialogFragment newFragment   new DatePickerFragment new OnDateSelectedObserver         newFragment show getFragmentManager     datePicker         Observer inner class  private class OnDateSelectedObserver implements Observer lt Integer gt          Override     public void onSubscribe Disposable d                 Override     public void onNext Integer integer             Here you invoke the logic              Override     public void onError Throwable e                 Override     public void onComplete                You can see the source code here  https   github com andresuarezz26 carpoolingapp

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The Communicating with Other Fragments guide says the Fragments should communicate through the associated Activity      Often you will want one Fragment to communicate with another  for   example to change the content based on a user event  All   Fragment-to-Fragment communication is done through the associated   Activity  Two Fragments should never communicate directly

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Maybe a bit late  but may help other people with the same question like I did   You can use setTargetFragment on Dialog before showing  and in dialog you can call getTargetFragment to get the reference

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I followed this simple steps to do this stuff    Create interface like DialogFragmentCallbackInterface with some method like callBackMethod Object data   Which you would calling to pass data  Now you can implement DialogFragmentCallbackInterface interface in your fragment like MyFragment implements DialogFragmentCallbackInterface  At time of DialogFragment creation set your invoking fragment MyFragment as target fragment who created DialogFragment use myDialogFragment setTargetFragment this  0  check setTargetFragment  Fragment fragment  int requestCode   MyDialogFragment dialogFrag   new MyDialogFragment    dialogFrag setTargetFragment this  1     Get your target fragment object into your DialogFragment by calling getTargetFragment   and cast it to DialogFragmentCallbackInterface Now you can use this interface to send data to your fragment   DialogFragmentCallbackInterface callback                DialogFragmentCallbackInterface  getTargetFragment    callback callBackMethod Object data     That s it all done  just make sure you have implemented this interface in your fragment

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Activity involved is completely unaware of the DialogFragment   Fragment class   public class MyFragment extends Fragment   int mStackLevel   0  public static final int DIALOG FRAGMENT   1    Override public void onCreate Bundle savedInstanceState        super onCreate savedInstanceState        if  savedInstanceState    null            mStackLevel   savedInstanceState getInt  level              Override public void onSaveInstanceState Bundle outState        super onSaveInstanceState outState       outState putInt  level   mStackLevel      void showDialog int type         mStackLevel         FragmentTransaction ft   getActivity   getFragmentManager   beginTransaction        Fragment prev   getActivity   getFragmentManager   findFragmentByTag  dialog        if  prev    null            ft remove prev             ft addToBackStack null        switch  type             case DIALOG FRAGMENT               DialogFragment dialogFrag   MyDialogFragment newInstance 123               dialogFrag setTargetFragment this  DIALOG FRAGMENT               dialogFrag show getFragmentManager   beginTransaction     dialog                 break            Override public void onActivityResult int requestCode  int resultCode  Intent data            switch requestCode                case DIALOG FRAGMENT                   if  resultCode    Activity RESULT OK                           After Ok code                    else if  resultCode    Activity RESULT CANCELED                          After Cancel code                                     break                         DialogFragment class   public class MyDialogFragment extends DialogFragment    public static MyDialogFragment newInstance int num        MyDialogFragment dialogFragment   new MyDialogFragment        Bundle bundle   new Bundle        bundle putInt  num   num       dialogFragment setArguments bundle        return dialogFragment       Override public Dialog onCreateDialog Bundle savedInstanceState         return new AlertDialog Builder getActivity                 setTitle R string ERROR               setIcon android R drawable ic dialog alert               setPositiveButton R string ok button                      new DialogInterface OnClickListener                             public void onClick DialogInterface dialog  int whichButton                                getTargetFragment   onActivityResult getTargetRequestCode    Activity RESULT OK  getActivity   getIntent                                                                                setNegativeButton R string cancel button  new DialogInterface OnClickListener                     public void onClick DialogInterface dialog  int whichButton                        getTargetFragment   onActivityResult getTargetRequestCode    Activity RESULT CANCELED  getActivity   getIntent                                                   create

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I am getting result to Fragment DashboardLiveWall calling fragment  from Fragment LiveWallFilterFragment receiving fragment   Like this      LiveWallFilterFragment filterFragment   LiveWallFilterFragment newInstance DashboardLiveWall this         getActivity   getSupportFragmentManager   beginTransaction      add R id frame container  filterFragment  addToBackStack     commit      where  public static LiveWallFilterFragment newInstance Fragment targetFragment String anyDummyData            LiveWallFilterFragment fragment   new LiveWallFilterFragment            Bundle args   new Bundle            args putString  dummyKey  anyDummyData           fragment setArguments args            if targetFragment    null              fragment setTargetFragment targetFragment  KeyConst LIVE WALL FILTER RESULT           return fragment          setResult back to calling fragment like  private void setResult boolean flag            if  getTargetFragment      null                Bundle bundle   new Bundle                bundle putBoolean  isWorkDone   flag               Intent mIntent   new Intent                mIntent putExtras bundle               getTargetFragment   onActivityResult getTargetRequestCode                        Activity RESULT OK  mIntent                     onActivityResult   Override     public void onActivityResult int requestCode  int resultCode  Intent data            super onActivityResult requestCode  resultCode  data            if  resultCode    Activity RESULT OK                if  requestCode    KeyConst LIVE WALL FILTER RESULT                     Bundle bundle   data getExtras                    if  bundle    null                         boolean isReset   bundle getBoolean  isWorkDone                        if  isReset                           else

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The correct way of setting a listener to a fragment is by setting it when it is attached  The problem I had was that onAttachFragment   was never called  After some investigation I realised that I had been using getFragmentManager instead of getChildFragmentManager  Here is how I do it   MyDialogFragment dialogFragment   MyDialogFragment newInstance  title    body    dialogFragment show getChildFragmentManager     SOME DIALOG      Attach it in onAttachFragment    Override public void onAttachFragment Fragment childFragment        super onAttachFragment childFragment        if  childFragment instanceof MyDialogFragment            MyDialogFragment dialog    MyDialogFragment  childFragment          dialog setListener new MyDialogFragment Listener                  Override             public void buttonClicked

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Kotlin guys here we go   So the problem we have is that we created an activity  MainActivity  on that activity we created a fragment  FragmentA and now we want to create a dialog fragment on top of FragmentA call it FragmentB  How do we get the results from FragmentB back to FragmentA without going through MainActivity   Note    FragmentA is a child fragment of MainActivity  To manage fragments created in FragmentA we will use childFragmentManager which does that  FragmentA is a parent fragment of FragmentB  to access FragmentA from inside FragmentB we will use parenFragment    Having said that  inside FragmentA   class FragmentA   Fragment    UpdateNameListener       override fun onSave name  String            toast  Running save with  name                 call this function somewhere in a clickListener perhaps     private fun startUpdateNameDialog             FragmentB   show childFragmentManager   started name dialog             Here is the dialog fragment FragmentB   class FragmentB   DialogFragment          private lateinit var listener  UpdateNameListener      override fun onAttach context  Context            super onAttach context          try               listener   parentFragment as UpdateNameListener           catch  e  ClassCastException                throw ClassCastException   context must implement UpdateNameListener                        override fun onCreateDialog savedInstanceState  Bundle    Dialog           return activity  let               val builder   AlertDialog Builder it              val binding   UpdateNameDialogFragmentBinding inflate LayoutInflater from context               binding btnSave setOnClickListener                   val name   binding name text toString                   listener onSave name                  dismiss                             builder setView binding root              return builder create                throw IllegalStateException  Activity can not be null             Here is the interface linking the two   interface UpdateNameListener       fun onSave name  String      That s it

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TargetFragment solution doesn t seem the best option for dialog fragments because it may create IllegalStateException after application get destroyed and recreated  In this case FragmentManager couldn t find the target fragment and you will get an IllegalStateException with a message like this       Fragment no longer exists for key android target state  index 1    It seems like Fragment setTargetFragment   is not meant for communication between a child and parent Fragment  but rather for communication between sibling-Fragments   So alternative way is to create dialog fragments like this by using the ChildFragmentManager of the parent fragment  rather then using the activities FragmentManager   dialogFragment show ParentFragment this getChildFragmentManager     dialog fragment      And by using an Interface  in onCreate method of the DialogFragment you can get the parent fragment    Override public void onCreate Bundle savedInstanceState        super onCreate savedInstanceState       try           callback    Callback  getParentFragment          catch  ClassCastException e            throw new ClassCastException  Calling fragment must implement Callback interface              Only thing left is to call your callback method after these steps   For more information about the issue  you can check out the link  https   code google com p android issues detail id 54520

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Updated   I made a library based on my gist code that generates those casting for you by using  CallbackFragment and  Callback   https   github com zeroarst callbackfragment   And the example give you the example that send a callback from a fragment to another fragment   Old answer   I made a BaseCallbackFragment and annotation  FragmentCallback  It currently extends Fragment  you can change it to DialogFragment and will work  It checks the implementations with the following order  getTargetFragment     getParentFragment     context  activity    Then you just need to extend it and declare your interfaces in your fragment and give it the annotation  and the base fragment will do the rest  The annotation also has a parameter mandatory for you to determine whether you want to force the fragment to implement the callback   public class EchoFragment extends BaseCallbackFragment        private FragmentInteractionListener mListener        FragmentCallback     public interface FragmentInteractionListener           void onEcho EchoFragment fragment  String echo             https   gist github com zeroarst 3b3f32092d58698a4568cdb0919c9a93

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You should define an interface in your fragment class and implement that interface in its parent activity   The details are outlined here http   developer android com guide components fragments html EventCallbacks    The code would look similar to   Fragment   public static class FragmentA extends DialogFragment        OnArticleSelectedListener mListener          Container Activity must implement this interface     public interface OnArticleSelectedListener           public void onArticleSelected Uri articleUri               Override     public void onAttach Activity activity            super onAttach activity           try               mListener    OnArticleSelectedListener  activity            catch  ClassCastException e                throw new ClassCastException activity toString       must implement OnArticleSelectedListener                        Activity   public class MyActivity extends Activity implements OnArticleSelectedListener                Override     public void onArticleSelected Uri articleUri

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I was facing a similar problem  The solution that I found out was     Declare an interface in your DialogFragment just like James McCracken has explained above  Implement the interface in your activity  not fragment  That is not a good practice   From the callback method in your activity  call a required public function in your fragment which does the job that you want to do    Thus  it becomes a two-step process   DialogFragment -  Activity and then Activity -  Fragment

[android] Callback to a Fragment from a DialogFragment

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