android - After Animation JSON load -

i new in android development.

i developing app in have add intro slides after animation end problem is, have data(image , title) json , show in slides. getting data unable update slides.

i have tried call json class animationend() getting null object reference.

please me. thankfull.

here code.

mainactivity

    public class mainactivity extends appcompatactivity implements      animation.animationlistener {      imageview img;     animation animfadein;      stringbuffer finalstring = new stringbuffer();      private textview title1, title2, title3;       @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_main);           getwindow().setflags(windowmanager.layoutparams.flag_fullscreen, windowmanager.layoutparams.flag_fullscreen);          img = (imageview) findviewbyid(r.id.imageview);         animfadein = animationutils.loadanimation(getapplicationcontext(), r.anim.fade_in);           animfadein.setanimationlistener(this);          img.startanimation(animfadein);         //img.startanimation(animzoomin);          title1 = (textview) findviewbyid(r.id.txt_title1);         title2 = (textview) findviewbyid(r.id.txt_title2);         title3 = (textview) findviewbyid(r.id.txt_title3);          //new jsontask().execute("https://www.prepforsure.com/engine/admin/mobileapi.php?action=addinto_api");      }      @override     public void onanimationstart(animation animation) {          new jsontask().execute("https://www.prepforsure.com/engine/admin/mobileapi.php?action=addinto_api");     }      @override     public void onanimationend(animation animation) {          intent = new intent(this, introactivity.class);         startactivity(i);          new jsontask().execute("https://www.prepforsure.com/engine/admin/mobileapi.php?action=addinto_api");       }      @override     public void onanimationrepeat(animation animation) {      }       public class jsontask extends asynctask<string, string, string> {          @override         protected string doinbackground(string... params) {             httpurlconnection connection = null;             bufferedreader reader = null;              try {                 url url = new url(params[0]);                 connection = (httpurlconnection) url.openconnection();                 connection.connect();                  inputstream inputstream = connection.getinputstream();                  reader = new bufferedreader(new inputstreamreader(inputstream));                  string line = "";                  stringbuffer buffer = new stringbuffer();                  while ((line = reader.readline()) != null) {                      buffer.append(line);                 }                 string finaljson = buffer.tostring();                  //get json array                  jsonarray parentarray = new jsonarray(finaljson);                   (int = 0; < parentarray.length(); i++) {                     jsonobject firstobject = parentarray.getjsonobject(i);                      string title = firstobject.getstring("title");                      finalstring.append(title + "\n");                  }                 //return buffer.tostring();                 return finalstring.tostring();               } catch (malformedurlexception e) {                 e.printstacktrace();             } catch (ioexception e) {                 e.printstacktrace();             } catch (jsonexception e) {                 e.printstacktrace();             } {                 if (connection != null) {                     connection.disconnect();                 }                 try {                      if (reader != null) {                         reader.close();                     }                 } catch (ioexception e) {                     e.printstacktrace();                 }             }             return null;         }          @override         protected void onpostexecute(string result) {             super.onpostexecute(result);              //toast.maketext(getapplicationcontext(), result, toast.length_long).show();              title1 = (textview) findviewbyid(r.id.txt_title1);             title1.settext(result);          }     }  } 

introactivity

 public class introactivity extends appcompatactivity {      private viewpager viewpager;     private viewpageradapter viewpageradapter;     private linearlayout dotslayout;     private textview[] dots;     private int[] layouts;     private button btnskip, btnnext;       @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_intro);           getwindow().setflags(windowmanager.layoutparams.flag_fullscreen, windowmanager.layoutparams.flag_fullscreen);           viewpager = (viewpager) findviewbyid(r.id.intro_view_pager);         dotslayout = (linearlayout) findviewbyid(r.id.layoutdots);         btnskip = (button) findviewbyid(r.id.btn_skip);         btnnext = (button) findviewbyid(r.id.btn_next);          layouts = new int[]{                 r.layout.slide1,                 r.layout.slide2,                 r.layout.slide3};           // adding bottom dots         addbottomdots(0);          viewpageradapter = new viewpageradapter();         viewpager.setadapter(viewpageradapter);         viewpager.addonpagechangelistener(viewpagerpagechangelistener);      }      @override     protected void onstart() {         super.onstart();     }      public void btnskipclick(view v) {          launchhomescreen();      }      public void btnnextclick(view v) {         // checking last page         // if last page home screen launched           int current = getitem(1);         if (current < layouts.length) {             // move next screen             viewpager.setcurrentitem(current);           } else {             launchhomescreen();         }     }       viewpager.onpagechangelistener viewpagerpagechangelistener = new viewpager.onpagechangelistener() {          @override         public void onpageselected(int position) {             addbottomdots(position);              // changing next button text 'next' / 'got it'             if (position == layouts.length - 1) {                 // last page. make button text got                 btnnext.settext(getstring(r.string.start));                 btnskip.setvisibility(view.gone);             } else {                 // still pages left                 btnnext.settext(getstring(r.string.next));                 btnskip.setvisibility(view.visible);             }         }          @override         public void onpagescrolled(int arg0, float arg1, int arg2) {          }          @override         public void onpagescrollstatechanged(int arg0) {          }     };       private void addbottomdots(int currentpage) {         dots = new textview[layouts.length];          dotslayout.removeallviews();         (int = 0; < dots.length; i++) {             dots[i] = new textview(this);             dots[i].settext(html.fromhtml("&#8226;"));             dots[i].settextsize(35);             dots[i].settextcolor(getresources().getcolor(r.color.dot_inactive));             dotslayout.addview(dots[i]);         }          if (dots.length > 0)             dots[currentpage].settextcolor(getresources().getcolor(r.color.dot_active));     }       private int getitem(int i) {         return viewpager.getcurrentitem() + i;     }      private void launchhomescreen() {         startactivity(new intent(this, welcome_activity.class));         finish();     }      public class viewpageradapter extends pageradapter {         private layoutinflater layoutinflater;           public viewpageradapter() {          }          @override         public object instantiateitem(viewgroup container, int position) {             layoutinflater = (layoutinflater) getsystemservice(context.layout_inflater_service);              view view = layoutinflater.inflate(layouts[position], container, false);             container.addview(view);              return view;         }          @override         public int getcount() {             return layouts.length;         }          @override         public boolean isviewfromobject(view view, object obj) {             return view == obj;         }           @override         public void destroyitem(viewgroup container, int position, object object) {             view view = (view) object;             container.removeview(view);         }     }  }