设计一个flutter页面，使用手机摄像头进行二维码扫描，可使用按钮控制，支持空安全，请列出依赖控件

好的，以下是一个使用手机摄像头进行二维码扫描的Flutter页面，支持空安全：

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:qr_code_scanner/qr_code_scanner.dart';

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

  @override
  _QRScannerPageState createState() => _QRScannerPageState();
}

class _QRScannerPageState extends State<QRScannerPage> {
  final GlobalKey qrKey = GlobalKey(debugLabel: 'QR');
  late QRViewController controller;
  bool isScanning = false;

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('QR Code Scanner'),
      ),
      body: Stack(
        children: [
          _buildQrView(context),
          Align(
            alignment: Alignment.bottomCenter,
            child: Padding(
              padding: const EdgeInsets.all(8.0),
              child: ElevatedButton(
                onPressed: isScanning ? _stopScan : _startScan,
                child: Text(isScanning ? 'Stop Scan' : 'Start Scan'),
              ),
            ),
          ),
        ],
      ),
    );
  }

  Widget _buildQrView(BuildContext context) {
    return QRView(
      key: qrKey,
      onQRViewCreated: _onQRViewCreated,
      overlay: QrScannerOverlayShape(
        borderColor: Theme.of(context).accentColor,
        borderRadius: 10,
        borderLength: 30,
        borderWidth: 10,
        cutOutSize: MediaQuery.of(context).size.width * 0.8,
      ),
      onPermissionSet: (ctrl, p) => _onPermissionSet(context, ctrl, p),
    );
  }

  void _onQRViewCreated(QRViewController controller) {
    setState(() {
      this.controller = controller;
    });
    controller.scannedDataStream.listen((scanData) {
      // Handle scanned data here
      print('Scanned Data: ${scanData.code}');
    });
  }

  void _onPermissionSet(BuildContext context, QRViewController ctrl, bool p) {
    if (!p) {
      showDialog(
        context: context,
        builder: (context) => AlertDialog(
          title: const Text('Camera Permission Required'),
          content: const Text('Please grant camera permission to use QR Scanner'),
          actions: [
            TextButton(
              onPressed: () => Navigator.pop(context),
              child: const Text('OK'),
            ),
          ],
        ),
      );
    }
  }

  void _startScan() {
    controller.resumeCamera();
    setState(() {
      isScanning = true;
    });
  }

  void _stopScan() {
    controller.pauseCamera();
    setState(() {
      isScanning = false;
    });
  }
}

依赖控件：

- `qr_code_scanner`: 用于扫描二维码的控件。
- `flutter_svg`: 如果您想要在扫描框中添加自定义的SVG图标，可以使用此库。
- `fluttertoast`: 用于显示扫描结果的提示信息。
- `permission_handler`: 用于请求相机权限。