text input validation halfway done

lib/addevent.dart

@@ -124,6 +124,9 @@ class _AddEventPageState extends State<AddEvent>  {
     final EventCurrentInstance currentEvent = EventCurrentInstance();
     String gnssStatusText = "";
 
+    final formKey = GlobalKey<FormState>(); //key for form
+
+
     if (true == syncGNSSData){
       // Update current event coordinates from GNSS stream
       currentEvent.store.latitude = lat;
@@ -149,12 +152,23 @@ class _AddEventPageState extends State<AddEvent>  {
           children: <Widget>[
             TextFormField(
               initialValue: currentEvent.store.label,
+              autovalidateMode: AutovalidateMode.onUserInteraction,
               decoration: const InputDecoration(
-                  labelText: 'Label'
+                  labelText: 'Label',
+                  errorText: 'Only: a-z , A-Z , _ , 0-9 , ,(Comma) , ( , ) , + , - , . , :'
               ),
               onChanged: (value) {
                 currentEvent.store.label = value;
               },
+              validator: (value){
+                if(!RegExp(r'^[a-z A-Z . \- 0-9 , ( ) + - _ :]+$').hasMatch(value!)){
+                  return "Only: a-z , A-Z , _ , 0-9 , ,(Comma) , ( , ) , + , - , . , :";
+                }else{
+                  currentEvent.store.label = value;
+                  return '';  // Entered Text is valid
+                }
+              },
+
             ),
             DropdownButtonFormField(
                 value: currentEvent.store.type,

lib/configuration.dart

@@ -43,6 +43,8 @@ Future<List<Device>> updateDevices(int collectionId) async {
 Future<List<Collection>> fetchCollections() async {
   debugPrint("Fetching Collections...");
   List<Collection> collectionList = [];
+  CollectionStoreInstance collections = CollectionStoreInstance();
+
   final response = await http
       .get(Uri.parse('https://sensor.awi.de/rest/sensors/collections/getAllCollections?pointInTime=2018-07-03T12%3A30%3A55.389Z'));
 
@@ -73,7 +75,6 @@ class _MyHomePageState extends State<Configuration> {
   @override
   void initState() {
     super.initState();
-    //futureCollection = fetchCollection();
     futureCollections = fetchCollections();
   }
   late Future<String> eventTypes;
@@ -109,10 +110,13 @@ class _MyHomePageState extends State<Configuration> {
 
                     /*Initialize active collection with first received
                     collection if not initialized yet*/
-                    if(activeCollection.store.collectionName == ''){
+                    if(activeCollection.store.id == -1){
                       activeCollection.store = collections.store[0];
                     }
 
+                    print(activeCollection.store);
+                    print(collections.store);
+
                     return DropdownButtonFormField(
                         value: activeCollection.store.collectionName,
                         decoration: const InputDecoration(