[android-developers] ORMLite NullPointerException on dao's create method

Creation of database and tables pass successfulyl. My onCreate() of DatabaseHandler class: 

public void onCreate(SQLiteDatabase db, ConnectionSource connectionSource) 
    {
         try
         {  

            TableUtils.createTable(connectionSource, Category.class);
            TableUtils.createTable(connectionSource, Level.class);
            DataParsing a = new DataParsing();
            a.fillCategories();
            Log.i(DatabaseHandler.class.getName(), "created new entries in onCreate: " );
         }
         catch (SQLException e){
             Log.e(TAG, "error creating DB " + DATABASE_NAME);
             throw new RuntimeException(e);
         } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

  I get data JSON from web service and parse it with GSON. Data fill the class data successfully in fillcategories() method. Then I want to put all the data into ORMLite database in saveContacts() method:  

  
   public class DataParsing {
    private static String KEY_STATUS = "status";
    private static String KEY_MESSAGE = "message";
    private static String KEY_CATEGORIES = "categories";
    private static String KEY_DATA = "data";
    private DatabaseHandler databaseHandler;
    private Context _context;
    public void fillCategories() throws JSONException, SQLException
    {   UserFunctions userFunction  = new UserFunctions();
        JSONObject json = userFunction.loginUser("login@ukr.net", "123456");
        JSONObject data = json.getJSONObject(KEY_DATA);
        // getting categories
        JSONArray categories = new JSONArray();
        categories = data.getJSONArray(KEY_CATEGORIES);
        Gson gson = new Gson();
        JsonParser parser = new JsonParser();
        JsonArray array = parser.parse(categories.toString()).getAsJsonArray();
        Type listType = new TypeToken<List<Category>>() {}.getType();
        List<Category> tasks = new ArrayList<Category>();
        tasks = gson.fromJson(array.toString(), listType);

        saveContacts(tasks);

    }

    public void saveContacts(List<Category> contacts) throws SQLException
        {

            OrmLiteSqliteOpenHelper dbHelper= DatabaseHandler.getInstance(_context);
            Dao<Category, Integer> daoContact=dbHelper.getDao(Category.class);

            QueryBuilder<Category, Integer> queryBuilder = daoContact.queryBuilder();
            Log.i("dao",queryBuilder.selectColumns("title").prepare().toString());


            for (Category contact : contacts) {
                Log.i("dao",contact.toString());
                HelperFactory.GetHelper().getCategoryDao().create(contact);
            }
        }
}
  And get the set of exceptions on the  

HelperFactory.GetHelper().getCategoryDao().create(contact);
  row:    08-02 10:32:02.119: E/AndroidRuntime(1026): FATAL EXCEPTION: main  08-02 10:32:02.119: E/AndroidRuntime(1026): java.lang.NullPointerException  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at com.library.DataParsing.saveContacts(DataParsing.java:61)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at com.library.DataParsing.fillCategories(DataParsing.java:45)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at com.library.DatabaseHandler.onCreate(DatabaseHandler.java:85)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at com.j256.ormlite.android.apptools.OrmLiteSqliteOpenHelper.onCreate(OrmLiteSqliteOpenHelper.java:169)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:126)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at com.j256.ormlite.android.AndroidConnectionSource.getReadWriteConnection(AndroidConnectionSource.java:63)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at com.j256.ormlite.android.AndroidConnectionSource.getReadOnlyConnection(AndroidConnectionSource.java:51)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at com.j256.ormlite.stmt.StatementExecutor.buildIterator(StatementExecutor.java:202)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at com.j256.ormlite.stmt.StatementExecutor.query(StatementExecutor.java:155)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at com.j256.ormlite.stmt.StatementExecutor.queryForAll(StatementExecutor.java:113)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at com.j256.ormlite.dao.BaseDaoImpl.queryForAll(BaseDaoImpl.java:237)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at com.assignmentexpert.LoginActivity$3.onClick(LoginActivity.java:121)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at android.view.View.performClick(View.java:2485)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at android.view.View$PerformClick.run(View.java:9080)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at android.os.Handler.handleCallback(Handler.java:587)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at android.os.Handler.dispatchMessage(Handler.java:92)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at android.os.Looper.loop(Looper.java:123)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at android.app.ActivityThread.main(ActivityThread.java:3687)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at java.lang.reflect.Method.invokeNative(Native Method)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at java.lang.reflect.Method.invoke(Method.java:507)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)  08-02 10:32:02.119: E/AndroidRuntime(1026): 	at dalvik.system.NativeStart.main(Native Method)  

What's the problem, tell me please. List of objects, which I pass to the saveContacts() method is filling succesfully. Tables of the database with corresponding rows were created successfully too...

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