Basic communication between two fragments

Question

I have one activity - MainActivity. Within this activity I have two fragments, both of which I created declaratively within the xml.

I am trying to pas

Answer 1

I give my activity an interface that all the fragments can then use. If you have have many fragments on the same activity, this saves a lot of code re-writing and is a cleaner solution / more modular than making an individual interface for each fragment with similar functions. I also like how it is modular. The downside, is that some fragments will have access to functions they don't need.

    public class MyActivity extends AppCompatActivity
    implements MyActivityInterface {

        private List mData; 

        @Override
        public List getData(){return mData;}

        @Override
        public void setData(List data){mData = data;}
    }


    public interface MyActivityInterface {

        List getData(); 
        void setData(List data);
    }

    public class MyFragment extends Fragment {

         private MyActivityInterface mActivity; 
         private List activityData; 

         public void onButtonPress(){
              activityData = mActivity.getData()
         }

        @Override
        public void onAttach(Context context) {
            super.onAttach(context);
            if (context instanceof MyActivityInterface) {
                mActivity = (MyActivityInterface) context;
            } else {
                throw new RuntimeException(context.toString()
                        + " must implement MyActivityInterface");
            }
        }

        @Override
        public void onDetach() {
            super.onDetach();
            mActivity = null;
        }
    }