android - nullPointerException on SQLiteDatabase db = dbHelper.getWritableDatabase(); insert method of ContentProvider -

i got nullpointerexception on line, listview.setadapter(adapter); in main activity class, cannot figure out causing it, ideas?

oncreate method of mainactivity class

 public class mainactivity extends activity implements loadermanager.loadercallbacks<cursor>{  private simplecursoradapter adapter; private loadermanager loadermanager; private cursorloader cursorloader; private listview listview; private int primarykey; private string primarykeystring; private string testtitle; private string testtext; private static final int loader_id = 1;  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);      primarykey = 0;     testtitle = "test title";     testtext = "test text";      primarykeystring = string.valueof(primarykey);     getloadermanager().initloader(loader_id, null, this);     adapter = new simplecursoradapter(this, r.layout.row_layout, null,             new string[]{primarykeystring, testtitle, testtext}, new int[]{r.id.textview1, r.id.textview2, r.id.textview3},             adapter.no_selection);     listview = (listview) findviewbyid(r.id.listview1);     listview.setadapter(adapter);      // load database test values     loaddatabase();  }  // load database test data public void loaddatabase(){     uri mnewuri;      contentvalues mnewvalues = new contentvalues();     mnewvalues.put(providerexample.noteitems.title, "test title");     mnewvalues.put(providerexample.noteitems.text, "test text value");      mnewuri = getcontentresolver().insert(providerexample.noteitems.content_uri, mnewvalues);  } 

the content provider class

 public class providerexample extends contentprovider {  public static final string database_name = "notes.db"; public static final int database_version = 1; public static final string table_name = "notes"; public static final string authority = "com.example.contentproviderexample.providerexample"; public static final urimatcher surimatcher; private static final int notes = 1; private static final int notes_id = 2; private static hashmap<string, string> notesprojectionmap;   static {         surimatcher = new urimatcher(urimatcher.no_match);         surimatcher.adduri(authority, table_name, notes);         surimatcher.adduri(authority, table_name + "/#", notes_id);     }   public static interface noteitems extends basecolumns {          // notes in content_uri plural actual table name singular version of word         public static final uri content_uri = uri.parse("content://" + authority + "/notes");         public static final string _id = "_id";         public static final string title = "title";         public static final string text = "text";         public static final string content_type = contentresolver.cursor_dir_base_type + "/vnd.example.providerexample";         // static final string single_record = "vnd.android.cursor.item/vnd.example.providerexample";         public static final string content_item_type = contentresolver.cursor_item_base_type + "/vnd.example.providerexample";         // static final string multiple_records = "vnd.android.cursor.dir/vnd.example.providerexample";          public static final string[] projection_all = {_id, title, text};         public static final string sort_order_default = title + " asc";   } // end lentitems interface   private static class databasehelper extends sqliteopenhelper{       databasehelper(context context){          super(context, database_name, null, database_version);      }       @override      public void oncreate(sqlitedatabase db) {      db.execsql("create table if not exists " + table_name + " (" + noteitems._id + "id integer primary key autoincrement, " +                noteitems.title + " text, " + noteitems.text + " text);");       }       @override      public void onupgrade(sqlitedatabase db, int previousversion, int newversion) {      db.execsql("drop table if exists " + table_name);      oncreate(db);      }   }  private databasehelper dbhelper;   @override public uri insert(uri uri, contentvalues initialvalues) {     if(surimatcher.match(uri)!=notes){     throw new illegalargumentexception("unknown uri" + uri);     }     contentvalues values;     if(initialvalues!=null){         values = new contentvalues(initialvalues);     }else{         values = new contentvalues();     }   sqlitedatabase db = dbhelper.getwritabledatabase(); // <--- nullpointerexception here     long rowid = db.insert(table_name, null, values);  if(rowid > 0){     uri noteuri = contenturis.withappendedid(noteitems.content_uri, rowid);     getcontext().getcontentresolver().notifychange(noteuri, null);     return noteuri; } throw new sqlexception("failed insert row " + uri);  } 

edit: nullpointerexception has changed sqlitedatabase db = dbhelper.getwritabledatabase(); of insert method

stakctrace:

androidruntime(19638): fatal exception: main androidruntime(19638): java.lang.runtimeexception: unable start activity componentinfo{com.example.contentproviderexample/com.example.contentproviderexample.mainactivity}: java.lang.nullpointerexception androidruntime(19638): caused by: java.lang.nullpointerexception androidruntime(19638):  @ com.example.contentproviderexample.providerexample.insert(providerexample.java:104) androidruntime(19638):  @ android.content.contentprovider$transport.insert(contentprovider.java:189) androidruntime(19638):  @ android.content.contentresolver.insert(contentresolver.java:730) androidruntime(19638):  @ com.example.contentproviderexample.mainactivity.loaddatabase(mainactivity.java:76) /androidruntime(19638):     @ com.example.contentproviderexample.mainactivity.oncreate(mainactivity.java:47) 

hard tell without stacktrace, seems null pointer isn't adapter, listview. looks haven't called setcontentview(), findviewbyid() method returning null, , you're trying set adapter null object.