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xue_hua_qr_code

Out-of-the-box QR code widget for Flutter. Pure Dart — no native dependencies, no platform channels.

XueHuaQrCode(value: 'https://example.com')

That is all you need: a scannable black-on-white QR code that adapts to its parent constraints.

Features

• One required parameter — pass value, get a standard QR code with sensible defaults
• Styling — square / circle / rounded modules, colors, gradients, proportional corner radius and gaps
• Center logo — ImageProvider based, sized as a fraction of the QR code, identical in widget and export
• Automatic mask selection — the best of 8 mask patterns is chosen per ISO/IEC 18004 penalty rules
• Robust error handling — empty / oversized content falls back to errorBuilder; a failing logo (e.g. network error) degrades to a plain, still-scannable QR code
• Export — XueHuaQrCode.toImage() and XueHuaQrCode.toPngBytes() share the exact painter used on screen

Installation

dependencies:
  xue_hua_qr_code: ^lasted_version

Basic usage

import 'package:xue_hua_qr_code/xue_hua_qr_code.dart';

// Adapts to the parent's shortest bounded side.
XueHuaQrCode(value: 'https://example.com')

// Fixed size.
XueHuaQrCode(value: 'https://example.com', size: 240)

Advanced usage

Custom style

XueHuaQrCode(
  value: 'https://example.com',
  size: 240,
  style: const QrStyle(
    shape: QrModuleShape.roundedSquare,
    moduleRadius: 0.4,          // fraction of a module, 0~0.5
    moduleGap: 0.15,            // fraction of a module, 0~0.5
    gradient: LinearGradient(colors: [Colors.pink, Colors.blue]),
    padding: EdgeInsets.all(12), // quiet zone
  ),
)

With a logo

XueHuaQrCode(
  value: 'https://example.com',
  size: 240,
  style: const QrStyle(shape: QrModuleShape.roundedSquare),
  logo: const QrLogo(
    image: AssetImage('assets/logo.png'), // NetworkImage / MemoryImage also work
    scale: 0.22,      // fraction of the QR side, max 0.35
    padding: 6,
    borderRadius: 8,
  ),
  // Error correction is automatically raised to `high` when a logo is present.
)

If the logo fails to load (missing asset, network error), the widget renders the full QR code without the logo — it never leaves an unscannable hole.

Error handling

XueHuaQrCode(
  value: userInput, // may be empty or too long
  errorBuilder: (context, error, stackTrace) => const Icon(Icons.error),
)

Export

// PNG bytes — save to a file or show with Image.memory.
final bytes = await XueHuaQrCode.toPngBytes(
  'https://example.com',
  size: 512,
  style: const QrStyle(shape: QrModuleShape.circle),
);

// dart:ui Image.
final image = await XueHuaQrCode.toImage('https://example.com', size: 512);

API reference

XueHuaQrCode

Parameter	Type	Default	Description
value	String	required	Content to encode
size	double?	null	Fixed side length; null adapts to parent constraints
style	QrStyle	QrStyle()	Visual style
logo	QrLogo?	null	Center logo
errorCorrectionLevel	QrErrorLevel?	auto	medium normally, high when a logo is set
errorBuilder	ImageErrorWidgetBuilder?	null	Fallback UI when encoding fails
semanticsLabel	String?	'QR code'	Accessibility label

QrStyle

Parameter	Type	Default	Description
shape	QrModuleShape	square	square / circle / roundedSquare
color	Color	black	Foreground color (ignored when gradient is set)
backgroundColor	Color	white	Background; pass Colors.transparent explicitly if needed
gradient	Gradient?	null	Foreground gradient (any Flutter Gradient)
moduleRadius	double?	per shape	Corner radius as a fraction of module size, 0~0.5
moduleGap	double?	per shape	Gap between modules as a fraction of module size, 0~0.5
padding	EdgeInsets	EdgeInsets.all(8)	Quiet zone around the code

QrLogo

Parameter	Type	Default	Description
image	ImageProvider	required	Logo image
scale	double	0.2	Logo side as a fraction of the QR side, max 0.35
padding	double	4	Backdrop padding around the logo (logical px)
backgroundColor	Color?	style background	Backdrop color
borderRadius	double	0	Backdrop corner radius (logical px)

QrErrorLevel

low (~7%), medium (~15%), quartile (~25%), high (~30%) — the approximate share of data that can be recovered.

Export

Method	Returns	Description
XueHuaQrCode.toImage(value, {size, style, logo, errorCorrectionLevel})	Future<ui.Image>	Render to a dart:ui image
XueHuaQrCode.toPngBytes(value, {size, style, logo, errorCorrectionLevel})	Future<Uint8List>	Render to PNG bytes

Both use the same painter as the widget — what you see is what you export.

Example app

cd example
flutter run

Five tabs demonstrate basic, circle, rounded, gradient, and logo styles, plus PNG export.

License

MIT — encoding internals ported from qrcode-kotlin.