android - unable to get data save in database in fragment containing recyclerview -

i'm working on integrating database save & contact information retrieved in fragment contain recyclerview. app directly crashing when started.

fatal exception: main process: com.example.admin.navigationdrawer_demo, pid: 15637 java.lang.runtimeexception: unable start activity componentinfo{com.example.admin.navigationdrawer_demo/com.example.admin.navigationdrawer_demo.mainactivity}: java.lang.nullpointerexception: attempt invoke virtual method 'android.database.sqlite.sqlitedatabase android.content.context.openorcreatedatabase(java.lang.string, int, android.database.sqlite.sqlitedatabase$cursorfactory, android.database.databaseerrorhandler)' on null object reference     @ android.app.activitythread.performlaunchactivity(activitythread.java:2416)     @ android.app.activitythread.handlelaunchactivity(activitythread.java:2476)     @ android.app.activitythread.-wrap11(activitythread.java)     @ android.app.activitythread$h.handlemessage(activitythread.java:1344)     @ android.os.handler.dispatchmessage(handler.java:102)     @ android.os.looper.loop(looper.java:148)     @ android.app.activitythread.main(activitythread.java:5417)     @ java.lang.reflect.method.invoke(native method)     @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:726)     @ com.android.internal.os.zygoteinit.main(zygoteinit.java:616) caused by: java.lang.nullpointerexception: attempt invoke virtual method 'android.database.sqlite.sqlitedatabase android.content.context.openorcreatedatabase(java.lang.string, int, android.database.sqlite.sqlitedatabase$cursorfactory, android.database.databaseerrorhandler)' on null object reference     @ android.database.sqlite.sqliteopenhelper.getdatabaselocked(sqliteopenhelper.java:223)     @ android.database.sqlite.sqliteopenhelper.getreadabledatabase(sqliteopenhelper.java:187)     @ com.example.admin.navigationdrawer_demo.person_db_openhelper.getallperson_mycontact(person_db_openhelper.java:149)     @ com.example.admin.navigationdrawer_demo.homefragment.filllistbirthdays(homefragment.java:64)     @ com.example.admin.navigationdrawer_demo.homefragment.oncreateview(homefragment.java:55)     @ android.support.v4.app.fragment.performcreateview(fragment.java:1974)     @ android.support.v4.app.fragmentmanagerimpl.movetostate(fragmentmanager.java:1067)     @ android.support.v4.app.fragmentmanagerimpl.movetostate(fragmentmanager.java:1252)     @ android.support.v4.app.backstackrecord.run(backstackrecord.java:742)     @ android.support.v4.app.fragmentmanagerimpl.execpendingactions(fragmentmanager.java:1617)     @ android.support.v4.app.fragmentcontroller.execpendingactions(fragmentcontroller.java:339)     @ android.support.v4.app.fragmentactivity.onstart(fragmentactivity.java:601)     @ android.app.instrumentation.callactivityonstart(instrumentation.java:1237)     @ android.app.activity.performstart(activity.java:6253)     @ android.app.activitythread.performlaunchactivity(activitythread.java:2379)     @ android.app.activitythread.handlelaunchactivity(activitythread.java:2476) 

i able create database

databasehelper.java:

public class person_db_openhelper extends sqliteopenhelper {      string tag="database";     public static string db_name="community_image.db";     public static int db_version=1;     public static string table_name="person_detail_image";          public static string col_id="_id";     private static final string col_key_image = "image";     public static string col_first_name="first_name";     public static string col_middle_name="middle_name";     public static string col_last_name="last_name";     public static string col_dob_string="date_of_birth_string";      public static string col_date="date";     public static string col_month="month";      public static string col_email_id_mandatory="email_id_mandatory";     public static string col_email_id="email_id";     public static string col_postal_address="postal_address";     public static string col_office_address="office_address";     public static string col_messanger_address="messanger_address";          private string create_table= "create table "+table_name+" (  "+             col_id+" integer primary key autoincrement, "+             col_key_image+" blob, "+             col_first_name+" text, "+             col_middle_name+" text, "+             col_last_name+" text, "+             col_dob_string+" text, "+             col_date+" long, "+             col_month+" long, "+             col_email_id+" text, "+             col_postal_address+" text, "+             col_office_address+" text, "+             col_messanger_address+" text);";             public person_db_openhelper(context context) {                 super(context,db_name,null,db_version);     }          @override     public void oncreate(sqlitedatabase db) {         log.d("create","table");         db.execsql(create_table);         }      @override     public void onupgrade(sqlitedatabase db, int i, int i1) {         db.execsql("drop table if exists " + table_name);         oncreate(db);         }          public long insertperson(person person)     {         sqlitedatabase database=getwritabledatabase();         contentvalues contentvalues=new contentvalues();          contentvalues.put(col_key_image,person.get_image());         contentvalues.put(col_first_name,person.getfirst_name());         contentvalues.put(col_middle_name,person.getmiddle_name());         contentvalues.put(col_last_name,person.getlast_name());         contentvalues.put(col_dob_string,person.getdob());          contentvalues.put(col_date,person.getdate1());         contentvalues.put(col_month,person.getmonth());         contentvalues.put(col_year,person.getyear());          contentvalues.put(col_doa,person.getdoa());             contentvalues.put(col_member_type,person.getmember_type());         contentvalues.put(col_phone_mandatory,person.getphone_mandatory());         contentvalues.put(col_phone,person.getphone());         contentvalues.put(col_land_line_number,person.getland_line_number());         contentvalues.put(col_email_id_mandatory,person.getemail_id_mandatory());         contentvalues.put(col_email_id,person.getemail_id());         contentvalues.put(col_postal_address,person.getpostal_address());         contentvalues.put(col_office_address,person.getoffice_address());         contentvalues.put(col_messanger_address,person.getmessanger_address());         log.d("object:","person"+person);              long inserted_record_row_id=database.insert(table_name,null,contentvalues);         return inserted_record_row_id;         }     // public cursor getallperson_mycontact()     public list<person> getallperson_mycontact()     {         list <person> listmycontacts=new arraylist<>();         sqlitedatabase database=getreadabledatabase();         cursor cursor_all_record=database.query(table_name,new string[]{col_id,col_first_name,col_middle_name,col_last_name,col_phone_mandatory},null,null,null,null,null);       //cursor cursor_all_record=database.query(table_name,new string[]{col_middle_name},null,null,null,null,null,null);         log.d(tag,"cursor  "+cursor_all_record.getcount());         while (cursor_all_record.movetonext())         {             person p=new person();              string name=cursor_all_record.getstring(1);             p.setfirst_name(name);            //  log.d("database", "name:- "+name);             listmycontacts.add(p);         }         //return cursor_all_record;             return listmycontacts;     }      @targetapi(build.version_codes.n)    

homefragment.java:

public class homefragment extends fragment     {     private context context;    // context context=getcontext();     person_db_openhelper person_db_openhelper=new person_db_openhelper(context);   //  event_db_openhelper event_db_openhelper=new event_db_openhelper(context);     private list<person> birthdays=new arraylist<>();     private list<event> events=new arraylist<>();     private list<person> aniversaries=new arraylist<>();      public homefragment() {     }      public static homefragment newinstance()     {         homefragment fragment = new homefragment();         return fragment;     }      public void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);     }      @override     public view oncreateview(layoutinflater inflater, viewgroup container, bundle savedinstancestate) {         view view = inflater.inflate(r.layout.fragment_main, container, false);         //context context = view.getcontext();         recyclerview recyclerview = (recyclerview) view;         filllistevents();         filllistbirthdays();         filllistaniversaries();          recyclerview.setlayoutmanager(new linearlayoutmanager(context));        recyclerview.setadapter(new homeadapter(birthdays,aniversaries,events));         return view;     }      private void filllistbirthdays() {         birthdays=person_db_openhelper.getallperson_mycontact();        /* birthday birthday;         (int = 0; < 2; i++) {             birthday = new birthday("birthday " + (i + 1));             birthdays.add(birthday);         }*/     }