Swiss QR Bill Library

The QR Bill library is a Flutter library for use in the development of Swiss payment QR bills and payment slips.

Features

The library is composed of three classes:

• QRBill. The purpose of this class is as a data class, similar to a POJO, for the storing and transport of QR-bill data. Additionally, this class can validate that the data contained conforms to the Swiss Payment Standards (currently version 2.2).
• QRGenerator. This class allows the generation of the actual QR image used by a QR-bill, without the payment slip. Input is in the form of a QRBill, while output may be a Widget or PNG binary data.
• BillGenerator. This class will produce the full formatted QR-bill payment slip, outputted as PNG binary data for a single QR-bill or a PDF document containing one or more QR-bills (one per page). Input is in the form of a QRBill for single images and a QRBill list for PDF documents. Supported languages are English, German, French and Italian.

Usage

Typically the QRBill class must always be imported as it is used as an input with the other two classes - either QRGenerator (for QR code generation) or BillGenerator (for payment slip / invoice generation).

A QR-bill Widget can be generated as follows:

Future<Widget> getQRBillWidget(String rawQrCode, double size) async {
    QRBill qrBill = QRBill(data: rawQrCode);
    Widget? qrWidget;
    if (qrBill.isValid()) {
      QRGenerator qr = QRGenerator(qrBill);
      qrWidget = await qr.getWidget(size: size);
    }

    if (qrWidget == null) {
      return SizedBox(
        width: size,
        height: size,
        child: const Center(child: Text("QR data incorrectly formatted!")),
      );
    } else {
      return qrWidget;
    }
  }

To output a PDF document containing multiple QR payment slips:

import 'package:flutter/material.dart';
import 'package:qr_bill/qr_bill.dart';
import 'package:qr_bill/bill_generator.dart';

Future<File?> getInvoicesBinary(
      List<QRBill> qrBills, File fileToWrite) async {
  BillGenerator bills = BillGenerator(
    qrBills, 
    language: BillGenerator.german);
  Uint8List? bill = await bills.generateInvoices();
  return bill == null ? null : await fileToWrite.writeAsBytes(bill);
}

Quick API Reference

QRBill

• QRBill QRBill({String data = ""}) Basic constructor.
• QRBill QRBill.fromJson(Map<String, dynamic> json) Deserializes the QRBill object from a JSON format.
• Map<String, dynamic> toJson() Serializes the QRBill object to a JSON format.
• String toString() Returns the QRBill object as a raw String used as the QR code.
• bool isValid() Returns if the QRBill strictly follows the specification.
• List<QRBillException> qrExceptions Returns a list of errors if the QRBill does not strictly follow the specification and an empty list if it does.
• Numerous getters and setters for the various Swiss QR bill attributes are also included.

QRGenerator

• QRGenerator QRGenerator(QRBill data) Basic constructor.
• Future<Widget?> getWidget({required double size, double margin = 0.05}) Outputs a single QR code (via the constructor) as a Flutter widget.
• Future<ByteData?> getBinary({required double size, double margin = 0.05}) Outputs the binary data of a single QR code (via the constructor), in a PNG format.
• drawCanvas(ui.Canvas c, {double margin = 0.0, required double size, Offset offset = const Offset(0.0, 0.0)}) Draws a single QR code (via the constructor), to a paint canvas. Principally used by BillGenerator.

BillGenerator

• BillGenerator BillGenerator(this.qrBills, {this.language = BillGenerator.english}) Basic constructor. Sets a list of QRBills for output, as well as the language to be employed.
• Future<Uint8List?> getBinary(QRBill qrBill) Outputs the binary data of a single Swiss QR bill payment slip, in a PNG format.
• Future<Uint8List?> generateInvoices() Outputs the binary data of all QRBills added with the constructor as Swiss QR bill payment slips, in a PDF format, one per page.