Android how to integrate an AsyncTask -

hi have app downloads json feed , starting become leggy know need use asynctask i'm not sure how integrate code know whats best way integrate it.

heres original code far

public class homeactivity extends listactivity {      private mergeadapter adapter=null;     private arrayadapter<string> arrayadapter=null;     private arrayadapter<string> arrayadapter2=null;     private lazyadapter arrayadapter3=null;     private static final string apikey = "7668hhf74hhd3dhhs";      private static final string apiuser = "androiduser";     private static string chosenleagueid = null;     private static string chosenmethod = null;      private static string chosenteamid = null;      public string fulldata = null;     public string newsfeedrequest = null;     public string newsfeedurl = null;     public string resultsfeedurl = null;     public string lastmonth = null;     public string hometeam = null;     public string awayteam = null;     public string homescore = null;     public string awayscore = null;     public string attendance = null;     public string division = null;     public string homescorers = null;     public string awayscorers = null;             public string resultsfeedrequest = null;     public string chosenleagueid = "40";     public list<string> newslist = null;     public list<string> newslist2 = null;     public list<string> newslist3 = null;     public list<string> imagelist = null;     public jsonobject resultsdict = null;     public view resultsview = null;        public int newsamount = 0;      long unixtimestamp = system.currenttimemillis() / 1000l;      //add time stamp url     //public string chosenmethod;      public class posttask extends asynctask<void, string, boolean> {          @override         protected boolean doinbackground(void... params) {             boolean result = false;          checkpreferences();               publishprogress("progress");             return result;         }          protected void onprogressupdate(string... progress) {             stringbuilder str = new stringbuilder();                 (int = 1; < progress.length; i++) {                     str.append(progress[i] + " ");                 }          }      }      static string buildhmacsignature(string pkey, string pstringtosign)     {       string lsignature = "none";       try       {         mac lmac = mac.getinstance("hmacsha256");         secretkeyspec lsecret = new secretkeyspec(pkey.getbytes(), "hmacsha256");         lmac.init(lsecret);          byte[] ldigest = lmac.dofinal(pstringtosign.getbytes());         biginteger lhash = new biginteger(1, ldigest);         lsignature = lhash.tostring(16);         if ((lsignature.length() % 2) != 0) {           lsignature = "0" + lsignature;         }       }       catch (nosuchalgorithmexception lex)       {         throw new runtimeexception("problems calculating hmac", lex);       }       catch (invalidkeyexception lex)       {         throw new runtimeexception("problems calculating hmac", lex);       }        return lsignature;     }          public void checkpreferences(){          sharedpreferences preferences = getsharedpreferences("prefs", context.mode_private);         chosenmethod = preferences.getstring("chosenmethod", chosenmethod);         chosenleagueid = preferences.getstring("chosenleagueid", chosenleagueid);         chosenteamid = preferences.getstring("chosenteamid", chosenteamid);                  log.v("lc", "newsurl" + newsfeedurl);           log.v("myapp", "chosenmethod home = " + chosenmethod);         log.v("myapp", "chosenleagueid home = " + chosenleagueid);         log.v("myapp", "chosenteamid home = " + chosenteamid);           if (chosenmethod.equals("team")) {              setcontentview(r.layout.homeactteam2);              newsamount = 5;              loaddata();             } else {              setcontentview(r.layout.homeact);              newsamount = 10;              loaddataleague();          }  }       public void loadresults(){      resultsfeedrequest = "1.0/league-website/" + chosenleagueid + "/results?&team_id=" + chosenteamid + "&limit=31&timestamp=" + unixtimestamp;     resultsfeedurl = "https://www.website.com/_services/api/" + resultsfeedrequest;       string myhash = buildhmacsignature(apikey, resultsfeedurl);      httpclient client = new defaulthttpclient();     httppost post = new httppost(resultsfeedurl);      list<namevaluepair> pairs = new arraylist<namevaluepair>();     pairs.add(new basicnamevaluepair("requesttoken", myhash));     pairs.add(new basicnamevaluepair("apiuser", apiuser));      try {         post.setentity (new urlencodedformentity(pairs));         httpresponse response = client.execute(post);         bufferedreader reader = new bufferedreader(new inputstreamreader(response.getentity().getcontent(), "utf-8"));         string json = reader.readline();         fulldata = string.valueof(json);         log.v("myapp","resultsdata" + fulldata);          newslist = new arraylist<string>();         newslist2 = new arraylist<string>();         newslist3 = new arraylist<string>();         imagelist = new arraylist<string>();           jsonobject obj = new jsonobject(json);             jsonobject objdata = obj.getjsonobject("data");         jsonarray jarray = objdata.getjsonarray("results");           if(jarray.length() < 1){              loadlastresults();          }else{              log.v("lc", "this month has results");          }   //       //         for(int t = 0; t < newsamount; t++){ //             jsonobject newstitledict = jarray.getjsonobject(t); //             imagelist.add(newstitledict.getstring("image_small")); //           newslist3.add(newstitledict.getstring("title")); //              //         } //       //         for(int t = 0; t < 1; t++){ //             jsonobject newstitledict = jarray.getjsonobject(t); //               //           newslist.add(newstitledict.getstring("title")); //           newslist2.add(newstitledict.getstring("title")); //              //         } //                } catch (clientprotocolexception e) {         // todo auto-generated catch block         e.printstacktrace();     } catch (ioexception e) {         // todo auto-generated catch block         e.printstacktrace();     } catch (jsonexception e) {         // todo auto-generated catch block         e.printstacktrace();     }   }       public void loadlastresults(){  resultsfeedrequest = "1.0/league-website/" + chosenleagueid + "/results?month=04&team_id=" + chosenteamid + "&limit=31&timestamp=" + unixtimestamp; resultsfeedurl = "https://www.website.com/_services/api/" + resultsfeedrequest;   string myhash = buildhmacsignature(apikey, resultsfeedurl);  date anothercurdate = new date();   simpledateformat formatter = new simpledateformat("mm");   string curmonth = formatter.format(anothercurdate);    int int = integer.parseint(curmonth);  int monthint = int -1;      curmonth = (string) (string.valueof(monthint));    if (curmonth.equals("1")){      lastmonth = "12";  }      else {     if(curmonth.length() < 2){         lastmonth = "0" + curmonth;     } else {         lastmonth = curmonth;     } }      log.v("lc","month= " + curmonth); log.v("lc","lastmonth= " + lastmonth);       httpclient client = new defaulthttpclient();     httppost post = new httppost(resultsfeedurl);      list<namevaluepair> pairs = new arraylist<namevaluepair>();     pairs.add(new basicnamevaluepair("requesttoken", myhash));     pairs.add(new basicnamevaluepair("apiuser", apiuser));      try {         post.setentity (new urlencodedformentity(pairs));         httpresponse response = client.execute(post);         bufferedreader reader = new bufferedreader(new inputstreamreader(response.getentity().getcontent(), "utf-8"));         string json = reader.readline();         fulldata = string.valueof(json);         log.v("myapp","resultsdata" + fulldata);          newslist = new arraylist<string>();         newslist2 = new arraylist<string>();         newslist3 = new arraylist<string>();         imagelist = new arraylist<string>();           jsonobject obj = new jsonobject(json);             jsonobject objdata = obj.getjsonobject("data");         jsonarray jarray = objdata.getjsonarray("results");              for(int t = 0; t < 1; t++){                 resultsdict = jarray.getjsonobject(t);               hometeam = resultsdict.getstring("hometeam");               awayteam = resultsdict.getstring("awayteam");               homescore = resultsdict.getstring("homescore");               awayscore = resultsdict.getstring("awayscore");               attendance = resultsdict.getstring("attendance");               division = resultsdict.getstring("division");                 log.v("lc","hometeam" + hometeam);               log.v("lc","awayteam" + awayteam);              }             resultsview = layoutinflater.from(getbasecontext()).inflate(r.layout.resultscell,                      null);             textview hometeam = (textview) resultsview.findviewbyid(r.id.hometeam);            hometeam.settext(hometeam);             textview awayteam = (textview) resultsview.findviewbyid(r.id.awayteam);            awayteam.settext(awayteam);             textview homescore = (textview) resultsview.findviewbyid(r.id.homescore);            homescore.settext(homescore);             textview awayscore = (textview) resultsview.findviewbyid(r.id.awayscore);            awayscore.settext(awayscore);             textview attendance = (textview) resultsview.findviewbyid(r.id.attendence);            attendance.settext("att:" + attendance);             textview division = (textview) resultsview.findviewbyid(r.id.division);            division.settext(division);                 log.v("lc", "resultsdict" + resultsdict);          } catch (clientprotocolexception e) {         // todo auto-generated catch block         e.printstacktrace();     } catch (ioexception e) {         // todo auto-generated catch block         e.printstacktrace();     } catch (jsonexception e) {         // todo auto-generated catch block         e.printstacktrace();     }   }            public void loadnews(){           newsfeedrequest = "1.0/league-website/" + chosenleagueid + "/news?timestamp=" + unixtimestamp;          newsfeedurl = "https://www.website.com/_services/api/" + newsfeedrequest;        string myhash = buildhmacsignature(apikey, newsfeedurl);        log.v("lc" , "resultsurl=" + resultsfeedurl);     httpclient client = new defaulthttpclient();     httppost post = new httppost(newsfeedurl);      list<namevaluepair> pairs = new arraylist<namevaluepair>();     pairs.add(new basicnamevaluepair("requesttoken", myhash));     pairs.add(new basicnamevaluepair("apiuser", apiuser));      try {         post.setentity (new urlencodedformentity(pairs));         httpresponse response = client.execute(post);         bufferedreader reader = new bufferedreader(new inputstreamreader(response.getentity().getcontent(), "utf-8"));         string json = reader.readline();         fulldata = string.valueof(json);         log.v("myapp","newsdata" + fulldata);          newslist = new arraylist<string>();         newslist2 = new arraylist<string>();         newslist3 = new arraylist<string>();         imagelist = new arraylist<string>();           jsonobject obj = new jsonobject(json);             jsonobject objdata = obj.getjsonobject("data");         jsonarray jarray = objdata.getjsonarray("news");         log.v("lc","newsamount= " + newsamount);             for(int t = 0; t < newsamount; t++){                jsonobject newstitledict = jarray.getjsonobject(t);                imagelist.add(newstitledict.getstring("image_small"));              newslist3.add(newstitledict.getstring("title"));             }             for(int t = 0; t < 1; t++){                jsonobject newstitledict = jarray.getjsonobject(t);           newslist.add(newstitledict.getstring("title")); //           newslist2.add(newstitledict.getstring("title"));             }        } catch (clientprotocolexception e) {         // todo auto-generated catch block         e.printstacktrace();     } catch (ioexception e) {         // todo auto-generated catch block         e.printstacktrace();     } catch (jsonexception e) {         // todo auto-generated catch block         e.printstacktrace();     }   }  public void mergeadaptersetup(){           arrayadapter = new arrayadapter<string>(this, r.layout.single_item, newslist);     arrayadapter2 = new arrayadapter<string>(this, r.layout.resultscell, newslist2);     //arrayadapter3 = new arrayadapter(this, r.layout.complex_item, newslist3);         string[] mstrings = (string[]) imagelist.toarray(new string[imagelist.size()]);      string[] news = (string[]) newslist3.toarray(new string[newslist3.size()]);          arrayadapter3 = new lazyadapter(this, mstrings, news);           listview list = getlistview();            list.settextfilterenabled(true);             layoutinflater inflater = (layoutinflater) this.getsystemservice(context.layout_inflater_service );             view header = inflater.inflate( r.layout.homeheader, list, false);             view header2 = inflater.inflate( r.layout.homeheader2, list, false);             view header3 = inflater.inflate( r.layout.homeheader3, list, false);       //setlistadapter (arrayadapter);           adapter = new mergeadapter();         adapter.addview(header);         adapter.addadapter(arrayadapter);         adapter.addview(header2);         adapter.addview(resultsview);         adapter.addview(header3);         adapter.addadapter(arrayadapter3);         setlistadapter(adapter); }  public void loaddataleague(){      string myhash = buildhmacsignature(apikey, newsfeedurl);       httpclient client = new defaulthttpclient();     httppost post = new httppost(newsfeedurl);      list<namevaluepair> pairs = new arraylist<namevaluepair>();     pairs.add(new basicnamevaluepair("requesttoken", myhash));     pairs.add(new basicnamevaluepair("apiuser", apiuser));      try {         post.setentity (new urlencodedformentity(pairs));         httpresponse response = client.execute(post);         bufferedreader reader = new bufferedreader(new inputstreamreader(response.getentity().getcontent(), "utf-8"));         string json = reader.readline();         fulldata = string.valueof(json);         log.v("myapp","newsdata" + fulldata);          newslist = new arraylist<string>();         newslist2 = new arraylist<string>();         newslist3 = new arraylist<string>();         imagelist = new arraylist<string>();           jsonobject obj = new jsonobject(json);             jsonobject objdata = obj.getjsonobject("data");         jsonarray jarray = objdata.getjsonarray("news");         log.v("lc","newsamount= " + newsamount);             for(int t = 0; t < newsamount; t++){                jsonobject newstitledict = jarray.getjsonobject(t);                imagelist.add(newstitledict.getstring("image_small"));              newslist3.add(newstitledict.getstring("title"));             }             for(int t = 0; t < 1; t++){                jsonobject newstitledict = jarray.getjsonobject(t);               newslist.add(newstitledict.getstring("title"));              newslist2.add(newstitledict.getstring("title"));             }        } catch (clientprotocolexception e) {         // todo auto-generated catch block         e.printstacktrace();     } catch (ioexception e) {         // todo auto-generated catch block         e.printstacktrace();     } catch (jsonexception e) {         // todo auto-generated catch block         e.printstacktrace();     }       arrayadapter = new arrayadapter<string>(this, r.layout.single_item, newslist);     arrayadapter2 = new arrayadapter<string>(this, r.layout.single_item, newslist2);     //arrayadapter3 = new arrayadapter(this, r.layout.complex_item, newslist3);       string[] mstrings = (string[]) imagelist.toarray(new string[imagelist.size()]);      string[] news = (string[]) newslist3.toarray(new string[newslist3.size()]);        arrayadapter3 = new lazyadapter(this, mstrings, news);           listview list = getlistview();            list.settextfilterenabled(true);             layoutinflater inflater = (layoutinflater) this.getsystemservice(context.layout_inflater_service );             view header3 = inflater.inflate( r.layout.homeheader3, list, false);       //setlistadapter (arrayadapter);           adapter = new mergeadapter();         adapter.addview(header3);         adapter.addadapter(arrayadapter3);         setlistadapter(adapter);      }         public void loaddata(){         loadresults();          loadnews();         mergeadaptersetup();     }      @override     protected void oncreate(bundle savedinstancestate) {         // todo auto-generated method stub         super.oncreate(savedinstancestate);          posttask jsontask;         jsontask = new posttask();         jsontask.execute();              button backbtn = (button) findviewbyid(r.id.backbtn);          //listening button event         backbtn.setonclicklistener(new view.onclicklistener() {              public void onclick(view arg0) {                 //starting new intent                 intent previousscreen = new intent(getapplicationcontext(), chooseteamactivity.class);                 chosenmethod = "null";                 sharedpreferences preferences = getsharedpreferences("prefs", context.mode_private);                 sharedpreferences.editor editor = preferences.edit();                 editor.putstring("chosenmethod", chosenmethod);                             editor.commit();                 previousscreen.putextra("fulldata", fulldata);                 startactivity(previousscreen);               }         });      }  @override public boolean oncreateoptionsmenu(menu menu) {     menuinflater inflater = getmenuinflater();     inflater.inflate(r.menu.menu, menu);     return true; }  @override public boolean onoptionsitemselected(menuitem item) {      if (item.getitemid() == r.id.home) {          startactivity(new intent(homeactivity.this, homeactivity.class));          return(true);   }       if (item.getitemid() == r.id.match) {          startactivity(new intent(homeactivity.this, matchactivity.class));          return(true);   }        if (item.getitemid() == r.id.teams) {          startactivity(new intent(homeactivity.this, teamsactivity.class));          return(true);   }        if (item.getitemid() == r.id.twitter) {          startactivity(new intent(homeactivity.this, twitteractivity.class));          return(true);   }      if (item.getitemid() == r.id.info) {          startactivity(new intent(homeactivity.this, infoactivity.class));          return(true);   }       return(super.onoptionsitemselected(item));   }   } 

error

java.lang.nullpointerexception     06-07 12:56:34.338: e/androidruntime(2688):     @ android.app.activitythread.performlaunchactivity(activitythread.java:1821)     06-07 12:56:34.338: e/androidruntime(2688):     @ android.app.activitythread.handlelaunchactivity(activitythread.java:1842)     06-07 12:56:34.338: e/androidruntime(2688):     @ android.app.activitythread.access$1500(activitythread.java:132)     06-07 12:56:34.338: e/androidruntime(2688):     @ android.app.activitythread$h.handlemessage(activitythread.java:1038)     06-07 12:56:34.338: e/androidruntime(2688):     @ android.os.handler.dispatchmessage(handler.java:99)     06-07 12:56:34.338: e/androidruntime(2688):     @ android.os.looper.loop(looper.java:143)     06-07 12:56:34.338: e/androidruntime(2688):     @ android.app.activitythread.main(activitythread.java:4263)     06-07 12:56:34.338: e/androidruntime(2688):     @ java.lang.reflect.method.invokenative(native method)     06-07 12:56:34.338: e/androidruntime(2688):     @ java.lang.reflect.method.invoke(method.java:507)     06-07 12:56:34.338: e/androidruntime(2688):     @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:839)     06-07 12:56:34.338: e/androidruntime(2688):     @ com.android.internal.os.zygoteinit.main(zygoteinit.java:597)     06-07 12:56:34.338: e/androidruntime(2688):     @ dalvik.system.nativestart.main(native method)     06-07 12:56:34.338: e/androidruntime(2688): caused by: java.lang.nullpointerexception     06-07 12:56:34.338: e/androidruntime(2688):     @ homeactivity.oncreate(homeactivity.java:637)     06-07 12:56:34.338: e/androidruntime(2688):     @ android.app.instrumentation.callactivityoncreate(instrumentation.java:1072)     06-07 12:56:34.338: e/androidruntime(2688):     @ android.app.activitythread.performlaunchactivity(activitythread.java:1785) 

hers example of async task, should put in async task because in android 3.0 > there rules not...

you need put in async task, not run in main thread in 3.0 >

use this:

public class jsontask extends asynctask<void, string, boolean> {          @override         protected boolean doinbackground(void... params) {             boolean result = false;              //all code goes in here               //if want on ui use progress update              publishprogress("progress");             return result;         }          protected void onprogressupdate(string... progress) {             stringbuilder str = new stringbuilder();                 (int = 1; < progress.length; i++) {                     str.append(progress[i] + " ");                 }          }     } 

you need reference outside async task

jsontask jsontask; 

then need start it

jsontask = new jsontask(); jsontask.execute(); 

i had exact same problem while ago, goodluck