Android ViewPager Frame Listview Crash -

i trying make tablayout (viewpager) app 3 fragments. in 1 of tabs, want display json parsed custom list view. custom list view , tab layout works fine individually (codes tutorial). when combine these two, app crashes immediately, couldn't figure out going wrong. hope guys can help

thank sam_0829....you saved me

the problems 1. instead of mainactivity, getmessages must in fragment

2. view empty while calling onviewcreated, declared private view variable

   private view v;

   //then oncreate

   view v = inflater.inflate(r.layout.message_tab, container, false);

   and passed

onviewcreated public void onviewcreated(view v, @nullable bundle savedinstancestate) { super.onviewcreated(v, savedinstancestate); contactlist = new arraylist<>();

    lv = (listview) v.findviewbyid(r.id.list);      new getmessages().execute(); } 

and life became awesome

thank yo sam taught me trouble shoot via logs...something never trusted before

message fragment (solved code) ->

    package com.example.user.newton;   public class messagetab extends fragment {     private string tag = mainactivity.class.getsimplename();      private progressdialog pdialog;     private listview lv;     private view v;     // url messages json      private static string url = "http://myjson.com/17oyz5";      arraylist<hashmap<string, string>> contactlist;     private mainactivity.sectionspageradapter msectionspageradapter;     @override     public view oncreateview(layoutinflater inflater, viewgroup container,                              bundle savedinstancestate) {         // inflate layout fragment         view v =  inflater.inflate(r.layout.message_tab, container, false);         return v;     }     private class getmessages extends asynctask<void, void, void> {          @override         protected void onpreexecute() {             super.onpreexecute();             // showing progress dialog             pdialog = new progressdialog(getactivity());             pdialog.setmessage("please wait...");             pdialog.setcancelable(false);             pdialog.show();          }          @override         protected void doinbackground(void... arg0) {             httphandler sh = new httphandler();              // making request url , getting response             string jsonstr = sh.makeservicecall(url);              log.e(tag, "response url: " + jsonstr);              if (jsonstr != null) {                 try {                     jsonobject jsonobj = new jsonobject(jsonstr);                      // getting json array node                     jsonarray messages = jsonobj.getjsonarray("messages");                      // looping through messages                     (int = 0; < messages.length(); i++) {                         jsonobject c = messages.getjsonobject(i);                          string message= c.getstring("message");                         string sender= c.getstring("sender");                         string mtime= c.getstring("time");                          hashmap<string, string> contact = new hashmap<>();                          // adding each child node hashmap key => value                         contact.put("message", message);                         contact.put("sender", sender);                         contact.put("mtime", mtime);                          contactlist.add(contact);                     }                 } catch (final jsonexception e) {                     log.e(tag, "json parsing error: " + e.getmessage());                     getactivity().runonuithread(new runnable() {                         @override                         public void run() {                             toast.maketext(getactivity(),                                     "json parsing error: " + e.getmessage(),                                     toast.length_long)                                     .show();                         }                     });                  }             } else {                 log.e(tag, "couldn't json server.");                 getactivity().runonuithread(new runnable() {                     @override                     public void run() {                         toast.maketext(getactivity(),                                 "couldn't json server. check logcat possible errors!",                                 toast.length_long)                                 .show();                     }                 });              }              return null;         }          @override         protected void onpostexecute(void result) {             super.onpostexecute(result);             // dismiss progress dialog             if (pdialog.isshowing())                 pdialog.dismiss();             /**              * updating parsed json data listview              * */             listadapter adapter = new simpleadapter(                     getactivity(), contactlist,                     r.layout.custom_layout, new string[]{"message", "sender",                     "mtime"}, new int[]{r.id.name,                     r.id.email, r.id.mobile});              lv.setadapter(adapter);         }      }      @override     public void onviewcreated(view v, @nullable bundle savedinstancestate) {         super.onviewcreated(v, savedinstancestate);         contactlist = new arraylist<>();          lv = (listview) v.findviewbyid(r.id.list);          new getmessages().execute();     } } 

messagefragment layout

<?xml version="1.0" encoding="utf-8"?> <linearlayout xmlns:android="http://schemas.android.com/apk/res/android"     android:orientation="vertical" android:layout_width="match_parent"     android:layout_height="match_parent">      <listview         android:id="@+id/list"         android:layout_width="match_parent"         android:layout_height="match_parent" /> </linearlayout> 

please change

pdialog = new progressdialog(getapplicationcontext()); 

to

pdialog = new progressdialog(mainactivity.this); 

& try.