android - Refresh tab fragment page on scroll -

i have 3 fragment tabs in viewpager.

fragment1 contains listfragment , fragment2 contains listfragment.

after clicking item in fragment2, should go fragment1 , refresh list. (the list populated via web service using gson). fragment2 passes value fragment1 can reload according parameter carried along.

i've tried many ways refresh/update state of list in fragment1 including reloading whole fragment1 oncreateview, using fragmenttransaction , calling host activity within itself. still couldn't find way make it.

also noticed upon scrolling tab 3 , tab 1, refreshes it. doesn't refresh list tab 2 tab 1. read solution in suggests set viewpager.setoffscreenpagelimit(0);, still problem persists.

here code currently.

in host activity (usershopactivity), i've implemented interface listener fragment2 (usercategoriesfragment) obtain category_id passed fragment1 (useritemsfragment):

public class usershopactivity extends fragmentactivity implements         usercategoriesfragment.onusercategoriesselectedlistener {  ...      @override     public void onusercategoriesselected(string category_id) {          settabuseritems(category_id);         string useritemsfragment = gettabuseritems();         useritemsfragment uif = (useritemsfragment) this.getsupportfragmentmanager().findfragmentbytag("android:switcher:"+r.id.pager+":0");          if (uif == null) {             setsavetouseritems(category_id);             log.d("useritemfragment: ", "null");         } else {             setsavetouseritems(category_id);             uif.updatecat(category_id);             log.d("cat id sent: ", useritemsfragment);              mviewpager.setcurrentitem(0);         }     }  } 

i have passed category_id. upon calling setcurrentitem(0), goes fragment1. want reload list. how?

in tabadapter, i've implemented viewpager.onpagechangelistener , override onpageselected method. believe should put refresh coding.

i've tried refresh fragment2 in method so:

@override public void onpageselected(int i) {     log.d("onpageselected: ", + "");     mactionbar.setselectednavigationitem(i);      if(i == 0) {        useritemsfragment uif = new useritemsfragment();        uif.reload();     } } 

and in reload() like:

public void reload(){    // re-call fragment within } 

however, got nullpointerexception error :(

can point me did wrong?

try this:

@override public void onpageselected(int i) {     log.d("onpageselected: ", + "");     mactionbar.setselectednavigationitem(i);      if(i == 0) {         useritemsfragment frg = (useritemsfragment)madapter.instantiateitem(viewpager, i);         frg.reload();     } }