qhd-prevention-flutter/lib/pages/home/scan_page.dart

import 'dart:io';
import 'dart:math' as math;

import 'package:flutter/material.dart';
import 'package:mobile_scanner/mobile_scanner.dart';
import 'package:qhd_prevention/pages/my_appbar.dart';
import 'package:image_picker/image_picker.dart';

class ScanPage extends StatefulWidget {
  const ScanPage({Key? key}) : super(key: key);

  @override
  State<ScanPage> createState() => _ScanPageState();
}

class _ScanPageState extends State<ScanPage> {
  final MobileScannerController _controller = MobileScannerController();
  bool _torchOn = false;

  @override
  void initState() {
    super.initState();
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  Future<void> _scanFromGallery() async {
    final picker = ImagePicker();
    final XFile? image = await picker.pickImage(source: ImageSource.gallery);
    if (image == null) return;

    try {
      // ★ 新版：返回 BarcodeCapture?
      final capture = await _controller.analyzeImage(image.path);
      if (capture != null && capture.barcodes.isNotEmpty) {
        final code = capture.barcodes.first.rawValue ?? '';
        _showResult(code);
      } else {
        _showResult('未识别到二维码/条码');
      }
    } catch (e) {
      _showResult('扫描失败：$e');
    }
  }

  void _showResult(String code) {
    showDialog(
      context: context,
      builder: (_) => AlertDialog(
        title: const Text('扫描结果'),
        content: Text(code),
        actions: [
          TextButton(
            onPressed: () {
              Navigator.of(context).pop();
              _controller.start(); // 恢复扫码
            },
            child: const Text('确定'),
          ),
        ],
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    // 中心扫描框大小
    const double scanSize = 250;
    final Size screen = MediaQuery.of(context).size;
    final double left = (screen.width - scanSize) / 2;
    final double top = (screen.height - scanSize) / 3 - kToolbarHeight;
    // 因为 SafeArea + AppBar 占了高度，所以减去 toolbar 高度
    const double cornerSize = 20.0; // 角标正方形区域大小
    const double strokeWidth = 4.0; // 边线宽度
    return Scaffold(
      appBar: MyAppbar(
        title: "二维码/条码扫描",
        actions: [
          TextButton(
            onPressed: _scanFromGallery,
            child: const Text(
              "相册",
              style: TextStyle(color: Colors.white, fontSize: 16),
            ),
          ),
        ],
      ),
      body: Stack(
        children: [
          // 1. 摄像头预览
          MobileScanner(
            controller: _controller,
            onDetect: (capture) {
              for (final barcode in capture.barcodes) {
                final code = barcode.rawValue;
                if (code != null && mounted) {
                  _controller.stop();
                  _showResult(code);
                  break;
                }
              }
            },
          ),

          // 2. 半透明遮罩
          // 顶部
          // 1. 顶部遮罩
          Positioned(
            left: 0, right: 0, top: 0,
            height: top,                  // 从顶到底部到扫描框上边缘
            child: Container(color: Colors.black54),
          ),

          // 2. 底部遮罩
          Positioned(
            left: 0, right: 0,
            top: top + scanSize,          // 从扫描框下边缘开始
            bottom: 0,
            child: Container(color: Colors.black54),
          ),

          // 3. 左侧遮罩
          Positioned(
            left: 0,
            top: top,
            width: left,                  // 从屏幕左侧到扫描框左边缘
            height: scanSize,             // 和扫描框一样高
            child: Container(color: Colors.black54),
          ),

          // 4. 右侧遮罩
          Positioned(
            left: left + scanSize,
            top: top,
            right: 0,
            height: scanSize,             // 和扫描框一样高
            child: Container(color: Colors.black54),
          ),

          // 3. 扫描框四个角
          // 左上
          Positioned(
            left: left,
            top: top,
            child: _corner(size: cornerSize, stroke: strokeWidth),
          ),
          // 右上
          Positioned(
            left: left + scanSize - cornerSize,
            top: top,
            child: _corner(size: cornerSize, stroke: strokeWidth, rotation: 1),
          ),
          // 左下
          Positioned(
            left: left,
            top: top + scanSize - cornerSize,
            child: _corner(size: cornerSize, stroke: strokeWidth, rotation: 3),
          ),
          // 右下
          Positioned(
            left: left + scanSize - cornerSize,
            top: top + scanSize - cornerSize,
            child: _corner(size: cornerSize, stroke: strokeWidth, rotation: 2),
          ),

          // 闪光灯按钮
          Positioned(
            left: (screen.width - 40) / 2,
            top: top + scanSize - 60,
            child: IconButton(
              iconSize: 32,
              color: Colors.white,
              icon: Icon(_torchOn ? Icons.flashlight_off_outlined : Icons.flashlight_on_outlined),
              onPressed: () {
                _controller.toggleTorch();
                setState(() {
                _torchOn = !_torchOn;
                });
              },
            ),
          ),
        ],
      ),
    );
  }

  /// 角装饰：一个 L 形的蓝色粗边
  Widget _corner({
    double size = 20,
    double stroke = 4,
    int rotation = 0, // 0=左上, 1=右上, 2=右下, 3=左下
  }) {
    return Transform.rotate(
      angle: rotation * math.pi / 2,
      child: Container(
        width: size,
        height: size,
        decoration: BoxDecoration(
          border: Border(
            top: BorderSide(color: Colors.blue, width: stroke),
            left: BorderSide(color: Colors.blue, width: stroke),
          ),
        ),
      ),
    );
  }

}