android - How do I link child fragments to the MainActivity? -

i'm building simple nba app since i'm new this.

the mainactivity has listview 2 items. western teams , eastern teams. when user taps on item, shows teams of conference. these teams stored array items in strings.xml file.

here mainactivity:

    public class mainactivity extends actionbaractivity {  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);     if (savedinstancestate == null) {         getsupportfragmentmanager().begintransaction()                 .add(r.id.container, new placeholderfragment())                 .commit();     } }   @override public boolean oncreateoptionsmenu(menu menu) {     // inflate menu; adds items action bar if present.     getmenuinflater().inflate(r.menu.main, menu);     return true; }  @override public boolean onoptionsitemselected(menuitem item) {     // handle action bar item clicks here. action bar     // automatically handle clicks on home/up button, long     // specify parent activity in androidmanifest.xml.     int id = item.getitemid();      //noinspection simplifiableifstatement     if (id == r.id.action_settings) {         return true;     }      return super.onoptionsitemselected(item); }  /**  * placeholder fragment containing simple view.  */ public static class placeholderfragment extends fragment {      arrayadapter<string> mconferenceadapter;      public placeholderfragment() {     }      @override     public view oncreateview(layoutinflater inflater, viewgroup container,                              bundle savedinstancestate) {          string[] conferencearray = {                 "western conference",                 "eastern conference"         };         list<string> conferencelist = new arraylist<string>(arrays.aslist(conferencearray));          mconferenceadapter =                 new arrayadapter<string>(                         getactivity(), // current context (this activity)                         r.layout.list_item_conferences, // name of layout id.                         r.id.list_item_conference_textview, // id of textview populate.                         conferencelist);          view rootview = inflater.inflate(r.layout.fragment_main, container, false);          // reference listview, , attach adapter it.         listview listview = (listview) rootview.findviewbyid(r.id.listview_conferences);         listview.setadapter(mconferenceadapter);         listview.setonitemclicklistener(new adapterview.onitemclicklistener() {              @override             public void onitemclick(adapterview<?> adapterview, view view, int position, long l) {                 string forecast = mconferenceadapter.getitem(position);                 intent intent = new intent(getactivity(), westernconference.class)                         .putextra(intent.extra_text, forecast);                 startactivity(intent);             }         });          return rootview;     } } 

the issue have no matter selection choose shows western teams.

this snippet westconference.java:

    public static class placeholderfragment extends fragment {      arrayadapter<string> mconferenceadapter;       public placeholderfragment() {     }      @override     public view oncreateview(layoutinflater inflater, viewgroup container,                              bundle savedinstancestate) {          // create dummy data listview.  here's sample weekly forecast         string[] teams = getresources().getstringarray(r.array.westteams);          list<string> conferencelist = new arraylist<string>(arrays.aslist(teams));           // have dummy forecast data, create arrayadapter.         // arrayadapter take data source (like our dummy forecast) ,         // use populate listview it's attached to.         mconferenceadapter =                 new arrayadapter<string>(                         getactivity(), // current context (this activity)                         r.layout.list_item_conferences, // name of layout id.                         r.id.list_item_conference_textview, // id of textview populate.                         conferencelist);          view rootview = inflater.inflate(r.layout.fragment_main, container, false);          // reference listview, , attach adapter it.         listview listview = (listview) rootview.findviewbyid(r.id.listview_conferences);         listview.setadapter(mconferenceadapter);          return rootview;     } } 

how can make if click west, loads teams, , if click east, loads eastern teams?