如何获取二维码的字符串值并将其存储到firebase中，以便链接到特定用户

我正在尝试通过QR扫描制作忠诚度应用程序，不确定如何获取生成给每个用户的QR码的字符串值，然后将其存储在firebase中，以便它链接到特定用户，然后更新链接到用户集合的子集合中扫描用户QR码的次数

QrImage(
                        data: '${user?.uid}',
                        version: QrVersions.auto,
                        size: 300,
                        errorStateBuilder: (cxt, err) {
                          return Container(
                            child: Center(
                              child: Text('Error',
                              textAlign: TextAlign.center,
                              style: new TextStyle(color: Colors.red),
                              ),
                              ),
                          );
                        },
                      ),

Future scan() async {
    try {
      String barcode = await BarcodeScanner.scan();
      setState(() => this.barcode = barcode);
    } on PlatformException catch (e) {
      if (e.code == BarcodeScanner.CameraAccessDenied) {
        setState(() {
          this.barcode = 'The user did not grant the camera permission!';
        });
      } else {
        setState(() => this.barcode = 'Unknown error: $e');
      }
    } on FormatException{
      setState(() => this.barcode = 'null (User returned using the "back"-button before scanning anything. Result)');
    } catch (e) {
      setState(() => this.barcode = 'Unknown error: $e');
    }
  }

这是我的QRImage，它为每个用户生成QR代码，但我不确定如何将数据值链接到firestore集合

QrImage(
                        data: '${user?.uid}',
                        version: QrVersions.auto,
                        size: 300,
                        errorStateBuilder: (cxt, err) {
                          return Container(
                            child: Center(
                              child: Text('Error',
                              textAlign: TextAlign.center,
                              style: new TextStyle(color: Colors.red),
                              ),
                              ),
                          );
                        },
                      ),

Future scan() async {
    try {
      String barcode = await BarcodeScanner.scan();
      setState(() => this.barcode = barcode);
    } on PlatformException catch (e) {
      if (e.code == BarcodeScanner.CameraAccessDenied) {
        setState(() {
          this.barcode = 'The user did not grant the camera permission!';
        });
      } else {
        setState(() => this.barcode = 'Unknown error: $e');
      }
    } on FormatException{
      setState(() => this.barcode = 'null (User returned using the "back"-button before scanning anything. Result)');
    } catch (e) {
      setState(() => this.barcode = 'Unknown error: $e');
    }
  }

这是我的扫描功能，在另一页上

用户集合

积分收集 试试这个

Future scan() async {
    try {
      String barcode = await BarcodeScanner.scan();
      setState(() => this.barcode = barcode);
      print("scanned sucsessfully");

      //plus one to points when scanned
      String userId = (await FirebaseAuth.instance.currentUser()).uid;
      final CollectionReference pointsCollection = Firestore.instance.collection("users");
      await pointsCollection.document(userId).collection('points').document(userId)
      .updateData({
        "points": FieldValue.increment(1),
        "transactions": FieldValue.increment(-1)
        });

    } on PlatformException catch (e) {
      if (e.code == BarcodeScanner.CameraAccessDenied) {
        setState(() {
          this.barcode = 'The user did not grant the camera permission!';
        });
      } else {
        setState(() => this.barcode = 'Unknown error: $e');
      }
    } on FormatException{
      setState(() => this.barcode = 'null (User returned using the "back"-button before scanning anything. Result)');
    } catch (e) {
      setState(() => this.barcode = 'Unknown error: $e');
    }
  }

试试这个

Future scan() async {
    try {
      String barcode = await BarcodeScanner.scan();
      setState(() => this.barcode = barcode);
      print("scanned sucsessfully");

      //plus one to points when scanned
      String userId = (await FirebaseAuth.instance.currentUser()).uid;
      final CollectionReference pointsCollection = Firestore.instance.collection("users");
      await pointsCollection.document(userId).collection('points').document(userId)
      .updateData({
        "points": FieldValue.increment(1),
        "transactions": FieldValue.increment(-1)
        });

    } on PlatformException catch (e) {
      if (e.code == BarcodeScanner.CameraAccessDenied) {
        setState(() {
          this.barcode = 'The user did not grant the camera permission!';
        });
      } else {
        setState(() => this.barcode = 'Unknown error: $e');
      }
    } on FormatException{
      setState(() => this.barcode = 'null (User returned using the "back"-button before scanning anything. Result)');
    } catch (e) {
      setState(() => this.barcode = 'Unknown error: $e');
    }
  }