You have to first check th database in databases folder(there is nothing )
then you have to copy the .db or .sqlite to data/data/databases folder
and than only u can open data base 
here is my sample code to do that:
public void createDataBase() throws IOException {
     boolean dbExist = checkDataBase();
     //boolean dbExist = false;
    if (dbExist) {
        // do nothing - database already exist
    } else {
        this.getReadableDatabase();
        try {
            copyDataBase();
        } catch (IOException e) {
            throw new Error("Error copying database");
        }
    }
}
// this method will check the existance of database
private boolean checkDataBase() {
    SQLiteDatabase checkDB = null;
    String myPath = DB_PATH + DB_NAME;
    try {
        checkDB = SQLiteDatabase.openDatabase(myPath, null,
                SQLiteDatabase.OPEN_READONLY);
    } catch (Exception e) {
    }
    if (checkDB != null) {
        checkDB.close();
    }
    return checkDB != null ? true : false;
}
// copy the database file from asset folder to the DDMS database folder
private void copyDataBase() throws IOException {
    // Open your local db as the input stream
    InputStream myInput = _context.getAssets().open(DB_NAME);
    // Path to the just created empty db
    String outFileName = DB_PATH + DB_NAME;
    // Open the empty db as the output stream
    OutputStream myOutput = new FileOutputStream(outFileName);
    // transfer bytes from the inputfile to the outputfile
    byte[] buffer = new byte[1024];
    int length;
    while ((length = myInput.read(buffer)) > 0) {
        myOutput.write(buffer, 0, length);
    }
    // Close the streams
    myOutput.flush();
    myOutput.close();
    myInput.close();
}
// open the database
public boolean openDataBase() throws SQLException {
    String mPath = DB_PATH + DB_NAME;
    // Log.v("mPath", mPath);
    db = SQLiteDatabase.openDatabase(mPath, null,
            SQLiteDatabase.CREATE_IF_NECESSARY);
    return db != null;
}