How to implement OnFragmentInteractionListener

Question

I have a wizard generated app with navigation drawer in android studio 0 8 2  I have created a fragment and added it with newInstance   and I get this error      com domain myapp E AndroidRuntime  FATAL EXCEPTION  main       java lang ClassCastException  com domain myapp MainActivity 422fb8f0  must implement   OnFragmentInteractionListener   I can t find anywhere how to implement this OnFragmentInteractionListener    It cannot be found even in android sdk documentation   MainActivity java  import android app Activity   import android app ActionBar  import android app Fragment  import android app FragmentManager  import android os Bundle  import android view LayoutInflater  import android view Menu  import android view MenuItem  import android view View  import android view ViewGroup  import android support v4 widget DrawerLayout    public class MainActivity extends Activity     implements NavigationDrawerFragment NavigationDrawerCallbacks           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         private CharSequence mTitle    Override protected void onCreate Bundle savedInstanceState        super onCreate savedInstanceState       setContentView R layout activity main        mNavigationDrawerFragment    NavigationDrawerFragment              getFragmentManager   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   getFragmentManager         switch  position            case 0  fragmentManager beginTransaction                    replace R id container  PlaceholderFragment newInstance position   1                    commit    break           case 1  fragmentManager beginTransaction                     replace R id container  AboutFragment newInstance  test1    test2                     commit    break     this crashes the app         case 2  fragmentManager beginTransaction                    replace R id container  BrowseQuotesFragment newInstance  test1    test2                     commit    break     this crashes the app           public void onSectionAttached int number        switch  number            case 1              mTitle   getString R string title section1               break          case 2              mTitle   getString R string title section2               break          case 3              mTitle   getString R string title section3               break           public void restoreActionBar         ActionBar actionBar   getActionBar        actionBar setNavigationMode ActionBar NAVIGATION MODE STANDARD       actionBar setDisplayShowTitleEnabled true       actionBar setTitle mTitle        Override public boolean onCreateOptionsMenu Menu menu        if   mNavigationDrawerFragment isDrawerOpen                 Only show items in the action bar relevant to this screen            if the drawer is not showing  Otherwise  let the drawer            decide what to show in the action bar          getMenuInflater   inflate R menu main  menu           restoreActionBar            return true            return super onCreateOptionsMenu menu       Override public boolean onOptionsItemSelected MenuItem item           Handle action bar item clicks here  The action bar will        automatically handle clicks on the Home Up button  so long        as you specify a parent activity in AndroidManifest xml      int id   item getItemId        if  id    R id action settings            return true            return super onOptionsItemSelected item             A placeholder fragment containing a simple view      public static class PlaceholderFragment extends Fragment                  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 PlaceholderFragment newInstance int sectionNumber            PlaceholderFragment fragment   new PlaceholderFragment            Bundle args   new Bundle            args putInt ARG SECTION NUMBER  sectionNumber           fragment setArguments args           return fragment             public PlaceholderFragment                 Override     public View onCreateView LayoutInflater inflater  ViewGroup container              Bundle savedInstanceState            View rootView   inflater inflate R layout fragment main  container  false           return rootView              Override     public void onAttach Activity activity            super onAttach activity             MainActivity  activity  onSectionAttached                  getArguments   getInt ARG SECTION NUMBER

User · Answer

OnFragmentInteractionListener is the default implementation for handling fragment to activity communication  This can be implemented based on your needs  Suppose if you need a function in your activity to be executed during a particular action within your fragment  you may make use of this callback method  If you don t need to have this interaction between your hosting activity and fragment  you may remove this implementation   In short you should implement the listener in your fragment hosting activity if you need the fragment-activity interaction like this  public class MainActivity extends Activity implements  YourFragment OnFragmentInteractionListener        and your fragment should have it defined like this  public interface OnFragmentInteractionListener          TODO  Update argument type and name     void onFragmentInteraction Uri uri       also provide definition for void onFragmentInteraction Uri uri   in your activity  or else just remove the listener initialisation from your fragment s onAttach if you dont have any fragment-activity interaction

User · Answer

Just an addendum   OnFragmentInteractionListener handle communication between Activity and Fragment using an interface  OnFragmentInteractionListener  and is created by default by Android Studio  but if you dont need to communicate with your activity  you can just get ride of  it   The goal is that you can attach your fragment to multiple activities and still reuse the same communication approach  Every activity could have its own OnFragmentInteractionListener for each fragment    But and if im sure my fragment will be attached to only one type of activity and i want to communicate with that activity   Then  if you dont want to use OnFragmentInteractionListener because of its verbosity  you can access your activity methods using     MyActivityClass  getActivity    someMethod

User · Answer

For those of you who visit this page looking for further clarification on this error  in my case the activity making the call to the fragment needed to have 2 implements in this case  like this   public class MyActivity extends Activity implements      MyFragment OnFragmentInteractionListener       NavigationDrawerFragment NaviationDrawerCallbacks             rest of the code

User · Answer

Answers posted here did not help  but the following link did   http   developer android com training basics fragments communicating html  Define an Interface  public class HeadlinesFragment extends ListFragment       OnHeadlineSelectedListener mCallback          Container Activity must implement this interface     public interface OnHeadlineSelectedListener           public void onArticleSelected int position               Override     public void onAttach Activity activity            super onAttach activity               This makes sure that the container activity has implemented            the callback interface  If not  it throws an exception         try               mCallback    OnHeadlineSelectedListener  activity            catch  ClassCastException e                throw new ClassCastException activity toString                           must implement OnHeadlineSelectedListener                                 For example  the following method in the fragment is called when the user clicks on a list item  The fragment uses the callback interface to deliver the event to the parent activity    Override public void onListItemClick ListView l  View v  int position  long id           Send the event to the host activity     mCallback onArticleSelected position       Implement the Interface  For example  the following activity implements the interface from the above example   public static class MainActivity extends Activity         implements HeadlinesFragment OnHeadlineSelectedListener               public void onArticleSelected int position               The user selected the headline of an article from the HeadlinesFragment            Do something here to display that article             Update for API 23  8 31 2015  Overrided method onAttach Activity activity  is now deprecated in android app Fragment  code should be upgraded to onAttach Context context    Override public void onAttach Context context        super onAttach context        Override public void onStart         super onStart        try           mListener    OnFragmentInteractionListener  getActivity          catch  ClassCastException e            throw new ClassCastException getActivity   toString                       must implement OnFragmentInteractionListener

User · Answer

I d like to add the destruction of the listener when the fragment is detached from the activity or destroyed    Override public void onDetach         super onDetach        mListener   null      and when using the new onStart   method with Context   Override public void onDestroy         super onDestroy        mListener   null

User · Answer

Just go to your fragment Activity and remove all method     instead on on createview method   your fragment has only on method oncreateview that s it     only this method implement other method delete    Override public View onCreateView LayoutInflater inflater  ViewGroup container          Bundle savedInstanceState        View rootView   inflater inflate R layout fragment main  container  false       return rootView      and make sure your layout it is demo for u

User · Answer

See your auto-generated Fragment created by Android Studio   When you created the new Fragment  Studio stubbed a bunch of code for you   At the bottom of the auto-generated template there is an inner interface definition called OnFragmentInteractionListener   Your Activity needs to implement this interface   This is the recommended pattern for your Fragment to notify your Activity of events so it can then take appropriate action  such as load another Fragment   See this page for details  look for the  Creating event callbacks for the Activity  section  http   developer android com guide components fragments html

User · Answer

You should try removing the following code from your fragments      try           mListener    OnFragmentInteractionListener  activity        catch  ClassCastException e            throw new ClassCastException activity toString                       must implement OnFragmentInteractionListener            The interface listener is a default created so that your activity and fragments can communicate easier

User · Answer

For those of you who still don t understand after reading  meda answer  here is my concise and complete explanation for this issue   Let s say you have 2 Fragments  Fragment A and Fragment B which are auto-generated from the app  On the bottom part of your generated fragments  you re going to find this code   public class Fragment A extends Fragment          rest of the code is omitted      public interface OnFragmentInteractionListener              TODO  Update argument type and name         public void onFragmentInteraction Uri uri            public class Fragment B extends Fragment          rest of the code is omitted      public interface OnFragmentInteractionListener              TODO  Update argument type and name         public void onFragmentInteraction Uri uri             To overcome the issue  you have to add onFragmentInteraction method into your activity  which in my case is named MainActivity2  After that  you need to implements all fragments in the MainActivity like this   public class MainActivity2 extends ActionBarActivity         implements Fragment A OnFragmentInteractionListener                      Fragment B OnFragmentInteractionListener                      NavigationDrawerFragment NavigationDrawerCallbacks         rest code is omitted       Override     public void onFragmentInteraction Uri uri             you can leave it empty           P S   In short  this method could be used for communicating between fragments  For those of you who want to know more about this method  please refer to this link

User · Answer

With me it worked delete this code    Override     public void onAttach Context context            super onAttach context           if  context instanceof OnFragmentInteractionListener                mListener    OnFragmentInteractionListener  context            else               throw new RuntimeException context toString                           must implement OnFragmentInteractionListener                      Ending like this    Override public void onAttach Context context        super onAttach context

User · Answer

In addition to  user26409021  s answer  If you have added a ItemFragment  The message in the ItemFragment is   Activities containing this fragment MUST implement the   link OnListFragmentInteractionListener  interface    And You should add in your activity   public class MainActivity extends AppCompatActivity     implements NavigationView OnNavigationItemSelectedListener  ItemFragment OnListFragmentInteractionListener      the code is omitted   public void onListFragmentInteraction DummyContent DummyItem uri         you can leave it empty     Here the dummy item is what you have on the bottom of your ItemFragment

User · Answer

Instead of Activity use context It works for me    Override     public void onAttach Context context            super onAttach context           try               mListener    OnFragmentInteractionListener  context            catch  ClassCastException e                throw new ClassCastException context toString                           must implement OnFragmentInteractionListener

[android] How to implement OnFragmentInteractionListener

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