Николай

public class DbHelper extends SQLiteOpenHelper {
    private static final String DB_NAME = "mydatabase.db";
    private static final String DB_DIRECTORY = "/data/data/com.example.sampleprogname/databases/";
    private static final String DB_FILEPATH = DB_DIRECTORY + DB_NAME;
    private static final int DB_VERSION = 4;

    private SQLiteDatabase db;
    private Context context;
    private static DbHelper dbHelper;

    public static DbHelper getInstance(Context context) {
        if (dbHelper == null) {
            // Хотя context приходит от конкретной активити, но это контекст application
            dbHelper = new DbHelper(context);
        }
        return dbHelper;
    }

    private DbHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
        this.context = context;

        if (dbExists()) {
            opendDb();
        } else {
            createDb();
        }
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }

    public void createDb() {
        if(!dbExists()) {
            this.getReadableDatabase();
            try {
                copyDbFromAssetsToDevice();
            } catch(IOException ex) {
                Log.e("db-copy", "Не удалось скопировать БД на устройство: " + ex.getMessage());
            }
        }
    }

    private void copyDbFromAssetsToDevice() throws IOException {
        try {
            InputStream istream = context.getAssets().open(DB_NAME);
            OutputStream ostream = new FileOutputStream(DB_FILEPATH);

            byte[] buffer = new byte[1024];
            int length;

            while ((length = istream.read(buffer)) > 0){
                ostream.write(buffer, 0, length);
            }

            ostream.flush();
            ostream.close();
            istream.close();
        } catch (Exception e) {
            Log.e("db-copy", e.getMessage());
        }
    }

    private boolean dbExists() {
        boolean dbExist = false;
        try {
            File dbfile = new File(DB_FILEPATH);
            dbExist = dbfile.exists();
        } catch(SQLiteException e) {
            Log.e("Database does not exists", e.getMessage());
        }
        return dbExist;
    }

    public void opendDb() throws SQLException {
        db = SQLiteDatabase.openDatabase(DB_FILEPATH, null, SQLiteDatabase.OPEN_READONLY);
    }

    public synchronized void closeDb() {
        if(db != null) {
            db.close();
        }
        super.close();
    }
}