fixed bug. It is no longer possible to start two sync processes in parallel

lib/viewevents.dart

@@ -2,7 +2,6 @@ import 'package:flutter/material.dart';
 import 'datamodel.dart';
 import 'sensorconnector.dart';
 import 'databaseconnector.dart';
-import 'package:getwidget/getwidget.dart';
 
 class ViewEvents extends StatefulWidget {
   const ViewEvents({Key? key}) : super(key: key);
@@ -23,65 +22,7 @@ class _ViewEvents extends State<ViewEvents> {
   bool _cancelSync = false;  //Flag to cancel sync process
   bool _currentlySyncing = false; // State flag to indicate if sync is ongoing
   var database = DatabaseInstance();
-
   List<Event> _localEvents = [];
-  Widget _buildSyncDialog(BuildContext context) {
-    SensorConnector sensorConnector = SensorConnector();
-
-    String startButtonText = '';
-    String closeButtonText = '';
-
-    if (_currentlySyncing == true){
-      startButtonText = 'Syncing';
-      closeButtonText = 'Cancel';
-    }else{
-      startButtonText = 'Start';
-      closeButtonText = 'Close';
-    }
-
-    return WillPopScope(
-        onWillPop: () async => false,
-        child: AlertDialog(
-          content: Column(
-            mainAxisSize: MainAxisSize.min,
-            crossAxisAlignment: CrossAxisAlignment.center,
-            children: <Widget>[
-              const Text('Syncing Events...'),
-              const SizedBox(height: 15.0),
-              GFProgressBar(
-                percentage: 0.7,  //Get percentage from global variable here
-                backgroundColor : Colors.black12,
-                progressBarColor: Colors.blue,
-              ),
-              const SizedBox(height: 5.0),
-              Text(_syncedEventCnt + ' / ' + _pendingEventCnt),
-              //TODO: show text XX pending events. count down
-            ],
-          ),
-          actions: <Widget>[
-            TextButton(
-              onPressed: () {
-                if(_currentlySyncing == false){
-                  syncEvents(); //Initiate sync
-                }
-              },
-              child: Text(startButtonText),  //Change text to Syncing... during Sync process.
-            ),
-            TextButton(
-              onPressed: () {
-                // Depending on state. Cancel or close. TODO: implement statemachine.
-                if(_currentlySyncing){
-                  _cancelSync = true; // Set flag so that async tasks stops syncing
-                }else{
-                  Navigator.of(context).pop();  // Close widget only if sync has stopped.
-                }
-              },
-              child: Text(closeButtonText),  // Change to Cancel during Sync process.
-            ),
-          ],
-        )
-    );
-  }
 
   Future<void> fetchEventsFromDb() async{
     final EventStoreInstance event = EventStoreInstance();
@@ -113,14 +54,15 @@ class _ViewEvents extends State<ViewEvents> {
   @override
   void dispose() async {
 
+    _cancelSync = true;
     /*Async update current configuration to shared preferences*/
     final EventStoreInstance event = EventStoreInstance();
     event.storeToSharedPrefs();
     super.dispose();
+    debugPrint("View Events disposed");
   }
 
   Future<void> syncEvents() async {
-
     _cancelSync = false;
     final ConfigurationStoreInstance configuration = ConfigurationStoreInstance();
     SensorConnector connection = SensorConnector();
@@ -140,6 +82,7 @@ class _ViewEvents extends State<ViewEvents> {
             configuration.loginInformation.password);
         var index = 0;
         for (var event in events) {
+          debugPrint("Check ABC");
           if(_cancelSync == true){
               _currentlySyncing = false;
               debugPrint('Sync process canceled');
@@ -151,14 +94,18 @@ class _ViewEvents extends State<ViewEvents> {
               event.toSensorJson().toString());
           index++;
           if (await connection.putEvent(event, token) == true) {
-            //Event has been posted to Sensor.
             syncCounter--;
-            debugPrint(
-                'put success, remaining events: ' + syncCounter.toString());
+            debugPrint('put success, now pending: ' + syncCounter.toString());
             event.status = 'EXPORTED'; //Update event to export only once
             database.updateEvent(event); //Update Event as exported in SQL Database
-            await fetchEventsFromDb(); //update view list   //TODO: this is bad for the sync performance!
-            setState(() {});
+            debugPrint('updated database');
+
+            ////Update view list TODO: this is bad for the sync performance!
+            await fetchEventsFromDb();
+            if(mounted) {
+              setState(() {});
+            }
+
           } else {
             throw Exception('Sync for ' + event.urn + 'failed');
           }
@@ -171,7 +118,9 @@ class _ViewEvents extends State<ViewEvents> {
         errorText = errorText.substring(10, errorText.length);  //Remove 'Exception' from string.
         _status = errorText;
         _statusStyle = const TextStyle(color: Colors.red);
-        setState(() {});
+        if(mounted) {
+          setState(() {});
+        }
       }
     }else{
       debugPrint('No PENDING event(s)');
@@ -330,15 +279,13 @@ class _ViewEvents extends State<ViewEvents> {
               icon: null,
               label: const Text('Sync'),
               onPressed: () {
-                syncEvents();
-
-                //showDialog(
-                //  barrierDismissible: false,
-                //  context: context,
-                //  builder: (BuildContext context) => _buildSyncDialog(context),
-                //);
-
 
+                if(_currentlySyncing == false){
+                  _currentlySyncing = true;
+                  syncEvents();
+                }else{
+                  debugPrint('Sync already running, will not start a second one');
+                }
               },
             ),
           ],