Setting image in android twitter integration -

i have app integrate android & twitter. application permission given while loading profile , fetching data profile, app stops responding. logcat shows nullpointerexception @ onpostexecution. so, have put image loading part of code under comments. can make change in comments app works image loading alongside it? here code profile fragment:

public class profilefragment extends fragment { textview prof_name; sharedpreferences pref; bitmap bitmap; imageview prof_img,tweet,signout,post_tweet; edittext tweet_text; progressdialog progress; dialog tdialog; string tweettext; @override public view oncreateview(layoutinflater inflater,viewgroup container, bundle args) {     view view = inflater.inflate(r.layout.profile_fragment, container, false);     prof_name = (textview)view.findviewbyid(r.id.prof_name);     pref = getactivity().getpreferences(0);     prof_img = (imageview)view.findviewbyid(r.id.prof_image);     tweet = (imageview)view.findviewbyid(r.id.tweet);     signout = (imageview)view.findviewbyid(r.id.signout);     signout.setonclicklistener(new signout());     tweet.setonclicklistener(new tweet());     new loadprofile().execute();     return view; } private class signout implements onclicklistener {      @override     public void onclick(view arg0) {         // todo auto-generated method stub         sharedpreferences.editor edit = pref.edit();         edit.putstring("access_token", "");         edit.putstring("access_token_secret", "");         edit.commit();           fragment login = new loginfragment();         fragmenttransaction ft = getactivity().getfragmentmanager().begintransaction();                        ft.replace(r.id.content_frame, login);         ft.settransition(fragmenttransaction.transit_fragment_fade);         ft.addtobackstack(null);         ft.commit();       }  } private class tweet implements onclicklistener {      @override     public void onclick(view v) {         // todo auto-generated method stub         tdialog = new dialog(getactivity());         tdialog.requestwindowfeature(window.feature_no_title);         tdialog.setcontentview(r.layout.tweet_dialog);         tweet_text = (edittext)tdialog.findviewbyid(r.id.tweet_text);         post_tweet = (imageview)tdialog.findviewbyid(r.id.post_tweet);         post_tweet.setonclicklistener(new view.onclicklistener() {              @override             public void onclick(view v) {                 // todo auto-generated method stub             new posttweet().execute();               }         });          tdialog.show();       }}  private class posttweet extends asynctask<string, string, string> {     @override         protected void onpreexecute() {             super.onpreexecute();             progress = new progressdialog(getactivity());             progress.setmessage("posting tweet ...");             progress.setprogressstyle(progressdialog.style_spinner);             progress.setindeterminate(true);             tweettext = tweet_text.gettext().tostring();             progress.show();      }        protected string doinbackground(string... args) {              configurationbuilder builder = new configurationbuilder();             builder.setoauthconsumerkey(pref.getstring("consumer_key", ""));             builder.setoauthconsumersecret(pref.getstring("consumer_secret", ""));                accesstoken accesstoken = new accesstoken(pref.getstring("access_token", ""), pref.getstring("access_token_secret", ""));             twitter twitter = new twitterfactory(builder.build()).getinstance(accesstoken);              try {                 twitter4j.status response = twitter.updatestatus(tweettext +" @learn2crack ");                 return response.tostring();             } catch (twitterexception e) {                 // todo auto-generated catch block                 e.printstacktrace();             }          return null;        }        protected void onpostexecute(string res) {            if(res != null){            progress.dismiss();            toast.maketext(getactivity(), "tweet sucessfully posted", toast.length_short).show();            tdialog.dismiss();            }else{                progress.dismiss();                toast.maketext(getactivity(), "error while tweeting !", toast.length_short).show();                tdialog.dismiss();            }         }    } private class loadprofile extends asynctask<string, string, bitmap> {     @override         protected void onpreexecute() {             super.onpreexecute();             progress = new progressdialog(getactivity());             progress.setmessage("loading profile ...");             progress.setprogressstyle(progressdialog.style_spinner);             progress.setindeterminate(true);             progress.show();      }        protected bitmap doinbackground(string... args) {          try {                bitmap = bitmapfactory.decodestream((inputstream)new url(pref.getstring("image_url", "")).getcontent());         } catch (exception e) {               e.printstacktrace();         }       return bitmap;        }        protected void onpostexecute(bitmap image) {           /* bitmap image_circle = bitmap.createbitmap(bitmap.getwidth(), bitmap.getheight(), bitmap.config.argb_8888);             bitmapshader shader = new bitmapshader (bitmap,  tilemode.clamp, tilemode.clamp);            paint paint = new paint();            paint.setshader(shader);            canvas c = new canvas(image_circle);            c.drawcircle(image.getwidth()/2, image.getheight()/2, image.getwidth()/2, paint);            prof_img.setimagebitmap(image_circle);*/            prof_name.settext("welcome " +pref.getstring("name", ""));             progress.hide();         }    } 

}