Null Object Reference Error: Android Studio using SQLite -

so i'm trying adapt tutorial: http://www.androidhive.info/2012/01/android-login-and-registration-with-php-mysql-and-sqlite/

to own project. basic register & login in android/java using sqlite & volley sql server via php. can tutorial written working no problem. however, upon transferring project encounter crash;

05-12 01:18:05.763    1965-1965/com.disclosure_scots.disclosure_scots e/androidruntime? fatal exception: main process: com.disclosure_scots.disclosure_scots, pid: 1965 java.lang.nullpointerexception: attempt invoke virtual method 'void com.disclosure_scots.disclosure_scots.appcontroller.addtorequestqueue(com.android.volley.request, java.lang.string)' on null object reference         @ com.disclosure_scots.disclosure_scots.registeractivity.registeruser(registeractivity.java:194)         @ com.disclosure_scots.disclosure_scots.registeractivity.access$300(registeractivity.java:34)         @ com.disclosure_scots.disclosure_scots.registeractivity$1.onclick(registeractivity.java:90)         @ android.view.view.performclick(view.java:4780)         @ android.view.view$performclick.run(view.java:19866)         @ android.os.handler.handlecallback(handler.java:739)         @ android.os.handler.dispatchmessage(handler.java:95)         @ android.os.looper.loop(looper.java:135)         @ android.app.activitythread.main(activitythread.java:5257)         @ java.lang.reflect.method.invoke(native method)         @ java.lang.reflect.method.invoke(method.java:372)         @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:903)         @ com.android.internal.os.zygoteinit.main(zygoteinit.java:698) 

the line within registeractivity refers is;

appcontroller.getinstance().addtorequestqueue(strreq, tag_string_req);     } 

the activities involved are;

registeractivity

    package com.disclosure_scots.disclosure_scots;  import android.app.progressdialog; import android.content.intent; import android.support.v7.app.actionbaractivity; import android.os.bundle; import android.util.log; import android.view.menu; import android.view.menuitem;  import com.disclosure_scots.disclosure_scots.appconfig; import com.disclosure_scots.disclosure_scots.appcontroller; import com.disclosure_scots.disclosure_scots.sqlitehandler; import com.disclosure_scots.disclosure_scots.sessionmanager;  import org.json.jsonexception; import org.json.jsonobject;  import java.util.hashmap; import java.util.map;  import android.view.view; import android.widget.button; import android.widget.checkbox; import android.widget.edittext; import android.widget.toast;  import com.android.volley.request.method; import com.android.volley.response; import com.android.volley.volleyerror; import com.android.volley.toolbox.stringrequest;   public class registeractivity extends actionbaractivity {      private static final string tag = registeractivity.class.getsimplename();     private button btnregister;     private edittext inputfullname;     private edittext inputemail;     private edittext inputpassword;     private edittext inputtel_no;     private edittext inputhome_add;     private edittext inputpostcode;     private checkbox inputpostal;     private progressdialog pdialog;     private sessionmanager session;     private sqlitehandler db;      @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_register);          inputfullname = (edittext) findviewbyid(r.id.edittextname);         inputemail = (edittext) findviewbyid(r.id.edittextemail);         inputpassword = (edittext) findviewbyid(r.id.edittextpass);         inputtel_no = (edittext) findviewbyid(r.id.edittextphone);         inputhome_add = (edittext) findviewbyid(r.id.edittextpost);         inputpostcode = (edittext) findviewbyid(r.id.edittextpostcode);         inputpostal = (checkbox) findviewbyid(r.id.postalcheckbox);         btnregister = (button) findviewbyid(r.id.btnregister);          // progress dialog         pdialog = new progressdialog(this);         pdialog.setcancelable(false);          // session manager         session = new sessionmanager(getapplicationcontext());          // sqlite database handler         db = new sqlitehandler(getapplicationcontext());          // check if user logged in or not         if (session.isloggedin()) {             // user logged in. take him legal disclaimer activity             intent intent = new intent(registeractivity.this,                     legaldiscactivity.class);             startactivity(intent);             finish();         }          // register button click event         btnregister.setonclicklistener(new view.onclicklistener() {             public void onclick(view view) {                 string name = inputfullname.gettext().tostring();                 string email = inputemail.gettext().tostring();                 string password = inputpassword.gettext().tostring();                  if (!name.isempty() && !email.isempty() && !password.isempty()) {                     registeruser(name, email, password);                 } else {                     toast.maketext(getapplicationcontext(),                             "please enter details!", toast.length_long)                             .show();                 }             }         });          // link login screen         /*btnlinktologin.setonclicklistener(new view.onclicklistener() {              public void onclick(view view) {                 intent = new intent(getapplicationcontext(),                         loginactivity.class);                 startactivity(i);                 finish();             }         });*/      }      /**      * function store user in mysql database post params(tag, name,      * email, password) register url      * */     private void registeruser(final string name, final string email,                               final string password) {         // tag used cancel request         string tag_string_req = "req_register";          pdialog.setmessage("registering ...");         showdialog();          stringrequest strreq = new stringrequest(method.post,                 appconfig.url_register, new response.listener<string>() {              @override             public void onresponse(string response) {                 log.d(tag, "register response: " + response.tostring());                 hidedialog();                  try {                     jsonobject jobj = new jsonobject(response);                     boolean error = jobj.getboolean("error");                     if (!error) {                         // user stored in mysql                         // store user in sqlite                         string uid = jobj.getstring("uid");                          jsonobject user = jobj.getjsonobject("user");                         string name = user.getstring("name");                         string email = user.getstring("email");                         string created_at = user                                 .getstring("created_at");                          // inserting row in users table                         db.adduser(name, email, uid, created_at);                          // launch login activity                         intent intent = new intent(                                 registeractivity.this,                                 loginactivity.class);                         startactivity(intent);                         finish();                     } else {                          // error occurred in registration. error                         // message                         string errormsg = jobj.getstring("error_msg");                         toast.maketext(getapplicationcontext(),                                 errormsg, toast.length_long).show();                     }                 } catch (jsonexception e) {                     e.printstacktrace();                 }              }         }, new response.errorlistener() {              @override             public void onerrorresponse(volleyerror error) {                 log.e(tag, "registration error: " + error.getmessage());                 toast.maketext(getapplicationcontext(),                         error.getmessage(), toast.length_long).show();                 hidedialog();             }         }) {              @override             protected map<string, string> getparams() {                 // posting params register url                 map<string, string> params = new hashmap<string, string>();                 params.put("tag", "register");                 params.put("name", name);                 params.put("email", email);                 params.put("password", password);                  return params;             }          };          // adding request request queue         appcontroller.getinstance().addtorequestqueue(strreq, tag_string_req);     }      private void showdialog() {         if (!pdialog.isshowing())             pdialog.show();     }      private void hidedialog() {         if (pdialog.isshowing())             pdialog.dismiss();     }       @override     public boolean oncreateoptionsmenu(menu menu) {         // inflate menu; adds items action bar if present.         getmenuinflater().inflate(r.menu.menu_register, menu);         return true;     }      @override     public boolean onoptionsitemselected(menuitem item) {         // handle action bar item clicks here. action bar         // automatically handle clicks on home/up button, long         // specify parent activity in androidmanifest.xml.         int id = item.getitemid();          //noinspection simplifiableifstatement         if (id == r.id.action_settings) {             return true;         }          return super.onoptionsitemselected(item);     } } 

appcontroller class

    package com.disclosure_scots.disclosure_scots;  /**  * created administrator on 09/05/2015.  */ import android.app.application; import android.text.textutils;  import com.android.volley.request; import com.android.volley.requestqueue; import com.android.volley.toolbox.volley;  public class appcontroller extends application {      public static final string tag = appcontroller.class.getsimplename();      private requestqueue mrequestqueue;      private static appcontroller minstance;      @override     public void oncreate() {         super.oncreate();         minstance = this;     }      public static synchronized appcontroller getinstance() {         return minstance;     }      public requestqueue getrequestqueue() {         if (mrequestqueue == null) {             mrequestqueue = volley.newrequestqueue(getapplicationcontext());         }          return mrequestqueue;     }      public <t> void addtorequestqueue(request<t> req, string tag) {         req.settag(textutils.isempty(tag) ? tag : tag);         getrequestqueue().add(req);     }      public <t> void addtorequestqueue(request<t> req) {         req.settag(tag);         getrequestqueue().add(req);     }      public void cancelpendingrequests(object tag) {         if (mrequestqueue != null) {             mrequestqueue.cancelall(tag);         }     } } 

i've been on number of times cannot tell why getting null object in copied version while original works fine. appreciated.

this because didn't register appcontroller in manifest getinstance returns null.