added functionality to scan qr- and barcodes

lib/bottom_navigation_bar_buttons/event/barwidget.dart

-import 'package:deggendorf_app/bottom_navigation_bar_buttons/event/qr_scanner.dart';
 import 'package:flutter/material.dart';
 import 'package:deggendorf_app/bottom_navigation_bar_buttons/event/imageslides.dart';
 import 'package:deggendorf_app/bottom_navigation_bar_buttons/event/infobox_text.dart';
+import 'package:deggendorf_app/bottom_navigation_bar_buttons/event/qr_scanner.dart';
 
 class BarWidget extends StatefulWidget {
   const BarWidget({Key? key, required this.barName}) : super(key: key);
@@ -33,7 +33,10 @@ class _BarWidgetState extends State<BarWidget> {
             )),
         floatingActionButton: FloatingActionButton(
           onPressed: () {
-            QrScanner();
+            Navigator.push(
+              context,
+              MaterialPageRoute(builder: (context) => QRViewExample()),
+            );
           },
           backgroundColor: Colors.green,
           child: Icon(Icons.qr_code_scanner),

lib/bottom_navigation_bar_buttons/event/qr_scanner.dart

-import 'package:flutter/cupertino.dart';
+
+import 'dart:developer';
+
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
+import 'package:qr_code_scanner/qr_code_scanner.dart';
 
+/*
 class QrScanner extends StatefulWidget {
   const QrScanner({Key? key}) : super(key: key);
 
@@ -14,3 +19,169 @@ class _QrScannerState extends State {
     return Scaffold(body: Container(color: Colors.greenAccent));
   }
 }
+ */
+
+
+
+class QRViewExample extends StatefulWidget {
+  const QRViewExample({Key? key}) : super(key: key);
+
+  @override
+  State<StatefulWidget> createState() => _QRViewExampleState();
+}
+
+class _QRViewExampleState extends State<QRViewExample> {
+  Barcode? result;
+  QRViewController? controller;
+  final GlobalKey qrKey = GlobalKey(debugLabel: 'QR');
+
+  // 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();
+
+      controller!.pauseCamera();
+
+
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: Column(
+        children: <Widget>[
+          Expanded(flex: 4, child: _buildQrView(context)),
+          Expanded(
+            flex: 1,
+            child: FittedBox(
+              fit: BoxFit.contain,
+              child: Column(
+                mainAxisAlignment: MainAxisAlignment.spaceEvenly,
+                children: <Widget>[
+                  if (result != null)
+                    Text(
+                        'Barcode Type: ${describeEnum(result!.format)}   Data: ${result!.code}')
+                  else
+                    const Text('Scan a code'),
+                  Row(
+                    mainAxisAlignment: MainAxisAlignment.center,
+                    crossAxisAlignment: CrossAxisAlignment.center,
+                    children: <Widget>[
+                      Container(
+                        margin: const EdgeInsets.all(8),
+                        child: ElevatedButton(
+                            onPressed: () async {
+                              await controller?.toggleFlash();
+                              setState(() {});
+                            },
+                            child: FutureBuilder(
+                              future: controller?.getFlashStatus(),
+                              builder: (context, snapshot) {
+                                return Text('Flash: ${snapshot.data}');
+                              },
+                            )),
+                      ),
+                      Container(
+                        margin: const EdgeInsets.all(8),
+                        child: ElevatedButton(
+                            onPressed: () async {
+                              await controller?.flipCamera();
+                              setState(() {});
+                            },
+                            child: FutureBuilder(
+                              future: controller?.getCameraInfo(),
+                              builder: (context, snapshot) {
+                                if (snapshot.data != null) {
+                                  return Text(
+                                      'Camera facing ${describeEnum(snapshot.data!)}');
+                                } else {
+                                  return const Text('loading');
+                                }
+                              },
+                            )),
+                      )
+                    ],
+                  ),
+                  Row(
+                    mainAxisAlignment: MainAxisAlignment.center,
+                    crossAxisAlignment: CrossAxisAlignment.center,
+                    children: <Widget>[
+                      Container(
+                        margin: const EdgeInsets.all(8),
+                        child: ElevatedButton(
+                          onPressed: () async {
+                            await controller?.pauseCamera();
+                          },
+                          child: const Text('pause',
+                              style: TextStyle(fontSize: 20)),
+                        ),
+                      ),
+                      Container(
+                        margin: const EdgeInsets.all(8),
+                        child: ElevatedButton(
+                          onPressed: () async {
+                            await controller?.resumeCamera();
+                          },
+                          child: const Text('resume',
+                              style: TextStyle(fontSize: 20)),
+                        ),
+                      )
+                    ],
+                  ),
+                ],
+              ),
+            ),
+          )
+        ],
+      ),
+    );
+  }
+
+  Widget _buildQrView(BuildContext context) {
+    // For this example we check how width or tall the device is and change the scanArea and overlay accordingly.
+    var scanArea = (MediaQuery.of(context).size.width < 400 ||
+        MediaQuery.of(context).size.height < 400)
+        ? 150.0
+        : 300.0;
+    // To ensure the Scanner view is properly sizes after rotation
+    // we need to listen for Flutter SizeChanged notification and update controller
+    return QRView(
+      key: qrKey,
+      onQRViewCreated: _onQRViewCreated,
+      overlay: QrScannerOverlayShape(
+          borderColor: Colors.red,
+          borderRadius: 10,
+          borderLength: 30,
+          borderWidth: 10,
+          cutOutSize: scanArea),
+      onPermissionSet: (ctrl, p) => _onPermissionSet(context, ctrl, p),
+    );
+  }
+
+  void _onQRViewCreated(QRViewController controller) {
+    setState(() {
+      this.controller = controller;
+    });
+    controller.scannedDataStream.listen((scanData) {
+      setState(() {
+        result = scanData;
+      });
+    });
+  }
+
+  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();
+  }
+}
\ No newline at end of file