我正在使用 qr_code_scanner 在 flutter 中扫描二维码。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();
}
}
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();
}
试试这个一定能解决问题!
@override
Widget build(BuildContext context) {
if (controller != null && mounted) {
controller!.pauseCamera();
controller!.resumeCamera();
}
如果您使用手电筒功能,请使用以下代码!
class QRScanner extends StatefulWidget {
const QRScanner({Key? key}) : super(key: key);
@override
State<StatefulWidget> createState() => _QRScannerState();
}
class _QRScannerState extends State<QRScanner> {
Barcode? result;
QRViewController? controller;
final GlobalKey qrKey = GlobalKey(debugLabel: 'QR');
bool isflash = false;
// 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();
controller!.resumeCamera();
}
controller!.resumeCamera();
}
@override
Widget build(BuildContext context) {
if (controller != null && mounted && !isflash) {
controller!.pauseCamera();
controller!.resumeCamera();
}
return Scaffold(
appBar:
appBar(context, backbutton: true, icon: true, notifications: true),
body: Stack(
children: <Widget>[
_buildQrView(context),
Column(
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
// if (result != null)
// Text(
// 'Barcode Type: ${describeEnum(result!.format)} Data: ${result!.code}',
// style: const TextStyle(color: Colors.white),
// )
// else
// const Text('Scan a code'),
Row(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
GestureDetector(
onTap: () async {
isflash = !isflash;
await controller?.toggleFlash();
setState(() {});
},
child: Container(
margin: const EdgeInsets.all(8),
child: FutureBuilder(
future: controller?.getFlashStatus(),
builder: (context, snapshot) {
return snapshot.data == false
? const Icon(
Icons.flash_off,
color: Colors.white,
)
: const Icon(Icons.flash_on, color: Colors.white);
},
),
),
),
GestureDetector(
onTap: () async {
await controller?.flipCamera();
setState(() {});
},
child: Container(
margin: const EdgeInsets.all(8),
child: FutureBuilder(
future: controller?.getCameraInfo(),
builder: (context, snapshot) {
if (snapshot.data != null) {
return const Icon(Icons.cameraswitch_rounded,
color: Colors.white);
} else {
return const SizedBox();
}
},
),
),
)
],
),
],
)
],
),
);
}
Widget _buildQrView(BuildContext context) {
var scanArea = (Get.width < 400 || Get.height < 400) ? 230.0 : 330.0;
return QRView(
key: qrKey,
onQRViewCreated: _onQRViewCreated,
overlay: QrScannerOverlayShape(
borderColor: buttonColor,
borderRadius: 2,
borderLength: 35,
borderWidth: 6,
cutOutSize: scanArea),
onPermissionSet: (ctrl, p) => _onPermissionSet(context, ctrl, p),
);
}
void _onQRViewCreated(QRViewController controller) {
setState(() {
this.controller = controller;
});
controller.scannedDataStream.listen((scanData) {
if (scanData != null) {
setState(() {
result = scanData;
});
Get.find<QRService>().updateResult(scanData.code);
// Get.defaultDialog(
// content: Text("${scanData.code}"),
// );
Get.back();
// Get.offAll(() => const QRmainScreen());
}
});
}
void _onPermissionSet(BuildContext context, QRViewController ctrl, bool p) {
log('${DateTime.now().toIso8601String()}_onPermissionSet $p');
if (!p) {
ScaffoldMessenger.of(context).showSnackBar(
const SnackBar(content: Text('no Permission')),
);
}
}
@override
void dispose() {
controller?.dispose();
super.dispose();
}
}
将恢复相机从初始状态移除
@override
void initState() {
super.initState();
//controller?.resumeCamera();
}
对我来说同样的问题。使用 qr_code_scanner 包。能够在调试时运行和扫描。但是当我进行发布构建时,我的页面上出现空屏幕。请帮忙。