Flutter qr_code_scanner 显示黑屏而不是扫描仪

Question

我正在使用 qr_code_scanner 扫描 flutter 中的二维码。这里的要点是它显示黑屏而不是扫描仪。我似乎无法启动 qr 阅读器。但假设我退出应用程序，就像将应用程序放在后台，然后再次进入应用程序，相机突然启动。似乎无法找到为什么相机无法在应用程序启动时启动。

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

  @override
  State<Home> createState() => _HomeState();
}

class _HomeState extends State<Home> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: QrScan(),
    );
  }
}

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

  @override
  State<QrScan> createState() => _QrScanState();
}

class _QrScanState extends State<QrScan> {
  final GlobalKey qrKey = GlobalKey(debugLabel: 'QR');
  Barcode? result;
  QRViewController? controller;

  @override
  void initState() {
    super.initState();
    controller?.resumeCamera();
  }

  // In order to get hot reload to work we need to pause the camera if the platform
  // is android, or resume the camera if the platform is iOS.
  @override
  void reassemble() {
    super.reassemble();
    if (Platform.isAndroid) {
      controller?.pauseCamera();
    } else if (Platform.isIOS) {
      controller?.resumeCamera();
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        children: <Widget>[
          Expanded(
            flex: 5,
            child: QRView(
              key: qrKey,
              onQRViewCreated: _onQRViewCreated,
              overlay: QrScannerOverlayShape(
                  borderRadius: 10, borderWidth: 5, borderColor: Colors.white),
            ),
          ),
          Expanded(
            flex: 1,
            child: Center(
              child: (result != null)
                  ? Text(
                      'Barcode Type: ${describeEnum(result!.format)}   Data: ${result?.code}')
                  : Text('Scan a code'),
            ),
          )
        ],
      ),
    );
  }

  void _onQRViewCreated(QRViewController controller) {
    this.controller = controller;
    controller.scannedDataStream.listen((scanData) {
      setState(() {
        result = scanData;
      });
    });
  }

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

Answer 1

尝试在 _onQRViewCreated 中暂停和恢复相机：

void _onQRViewCreated(QRViewController controller) {
    this.controller = controller;
    controller.scannedDataStream.listen((scanData) {
      setState(() {
        result = scanData;
      });
    });
    controller.pauseCamera();
    controller.resumeCamera();
  }