Android Sqlite Databases static/non static etc

I have a question regarding the the usage of sqlite databases on Android. The main problem I have is the error 'Cannot be referenced from a static context'

Basically I have different classes which would require access to the database therefore I figured the database should be static. The question is then how do I initialise the database in MainActivity?

public class MainActivity extends BlunoLibrary {

//start db//

public static StoredValuesDBHelper StoredValuesDB =  new StoredValuesDBHelper(this);
public static SQLiteDatabase db = StoredValuesDB.getWritableDatabase();
....
}

where my database class is (essentially from the google sql tutorial)

package com.example.healthcare;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.provider.BaseColumns;


public class StoredValuesDBHelper extends SQLiteOpenHelper {
    // If you change the database schema, you must increment the database version. 
    public static final int DATABASE_VERSION = 1;
    public static final String DATABASE_NAME = "StoredValues.db";
    private static final String TEXT_TYPE = " TEXT";
    private static final String COMMA_SEP = ",";


    public static abstract class ValueEntry implements BaseColumns {
        public static final String TABLE_NAME = "storedvalue";
        public static final String COLUMN_NAME_ENTRY_ID = "entryid";
        public static final String COLUMN_NAME_CONTENT = "content";
    }
    private static final String SQL_CREATE_ENTRIES =
            "CREATE TABLE " + ValueEntry.TABLE_NAME + " (" +
                ValueEntry.COLUMN_NAME_ENTRY_ID + TEXT_TYPE + COMMA_SEP +
                ValueEntry.COLUMN_NAME_CONTENT + TEXT_TYPE + COMMA_SEP +")";
    private static final String SQL_DELETE_ENTRIES =
            "DROP TABLE IF EXISTS " + ValueEntry.TABLE_NAME;

    public StoredValuesDBHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }


    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(SQL_CREATE_ENTRIES);

    }

    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // This database is only a cache for online data, so its upgrade policy is
        // to simply to discard the data and start over
        db.execSQL(SQL_DELETE_ENTRIES);
        onCreate(db);
    }
   public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        onUpgrade(db, oldVersion, newVersion);
    }
}

Any help is much appreciated!

I have near zero experience in java and android programming