Late initialising error in flutter while working with firebase - firebase

Question

I'm working on this app to help people find the fitting wine for their meal. Now I wanted the user to be able to select the specific meal he or she is currently enjoying to have a better prediction what wine fits best. Now I tried implementing that but I'm getting this late error field must be initialised... I think I know where its coming from but I dont know how to solve it this is the code of the screen:
class _AskSomellierStep4ScreenState extends State<AskSomellierStep4Screen> {
late QueryDocumentSnapshot<Map<String, dynamic>> _selectedSnapshot;
List<String> dataLabel = [
'Home',
'Search',
'Account',
];
late Future resultsLoaded;
getResults() async {
var data = await FirebaseFirestore.instance
.collection(widget.wineOrMeal)
.where('type', isEqualTo: widget.selectedCuisine)
.get();
setState(() {
allResults = data.docs;
});
filterResultsList();
return data.docs;
}
#override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Theme.of(context).scaffoldBackgroundColor,
body: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
...
Padding(
padding: const EdgeInsets.only(
left: 35,
top: 5,
),
child: SizedBox(
height: 370,
width: 320,
child: Center(
child: ListView.builder(
dragStartBehavior: DragStartBehavior.down,
scrollDirection: Axis.vertical,
itemCount: filteredResults.length,
itemBuilder: (context, index) => widget.mealVSWine
? PrefInformationCardWine(
snapShotDocument: filteredResults[index],
cardColor: Theme.of(context).primaryColor,
isSelected:
filteredResults[index] == _selectedSnapshot,
onSelected: () {
setState(() {
_selectedSnapshot = filteredResults[index];
});
},
)
: PrefInformationCardMeal(
snapShotDocument: filteredResults[index],
cardColor: Theme.of(context).primaryColor,
isSelected:
filteredResults[index] == _selectedSnapshot,
onSelected: () {
setState(() {
_selectedSnapshot = filteredResults[index];
});
},
),
),
),
)),
Padding(
padding: const EdgeInsets.only(
left: 35,
top: 25,
),
child: SubmitSettingChangesButton(
buttonText: 'Continue',
cancelText: 'Cancel',
cancelOnTap: () {
Navigator.pop(context);
},
continueOnTap: () {
Navigator.pushAndRemoveUntil(
context,
createRoute(FindingRecommendationScreen(
snapshotName: _selectedSnapshot,
)),
(route) => false);
},
),
),
...
If you need any further information just give me a note. I would be very thankful if you could help me with this:)
Code Screen 4:
class AskSomellierStep4Screen extends StatefulWidget {
const AskSomellierStep4Screen({
Key? key,
required this.stepDescription,
required this.wineOrMeal,
required this.mealVSWine,
required this.selectedCuisine,
}) : super(key: key);
final String wineOrMeal;
final String stepDescription;
final bool mealVSWine;
final String selectedCuisine;
#override
State<AskSomellierStep4Screen> createState() =>
_AskSomellierStep4ScreenState();
}
class _AskSomellierStep4ScreenState extends State<AskSomellierStep4Screen> {
QueryDocumentSnapshot<Map<String, dynamic>>? _selectedSnapshot;
List<String> dataLabel = [
'Home',
'Search',
'Account',
];
late Future resultsLoaded;
List<IconData> data = [
CustomIcons.home,
CustomIcons.search,
CustomIcons.user,
];
getResults() async {
var data = await FirebaseFirestore.instance
.collection(widget.wineOrMeal)
.where('type', isEqualTo: widget.selectedCuisine)
.get();
setState(() {
allResults = data.docs;
});
filterResultsList();
return data.docs;
}
List allResults = [];
List filteredResults = [];
onSearchChanged() {
print(searchController.text);
filterResultsList();
}
filterResultsList() {
var showResults = [];
if (searchController.text != '') {
// we have a search parameter
for (var searchSnapshot in allResults) {
var name = searchSnapshot['name'].toLowerCase();
if (name.contains(searchController.text.toLowerCase())) {
showResults.add(searchSnapshot);
}
}
} else {
// we do not have a search parameter
showResults = List.from(allResults);
}
setState(() {
filteredResults = showResults;
});
}
TextEditingController searchController = TextEditingController();
#override
void initState() {
super.initState();
searchController.addListener(onSearchChanged);
}
#override
void dispose() {
searchController.removeListener(onSearchChanged);
searchController.dispose();
super.dispose();
}
#override
void didChangeDependencies() {
super.didChangeDependencies();
resultsLoaded = getResults();
}
#override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Theme.of(context).scaffoldBackgroundColor,
body: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
HomeScreenHeader(
subText: 'Wine and Food',
mainText: 'Ask your Somellier',
boxWidth: 238,
),
Padding(
padding: const EdgeInsets.only(
left: 172,
top: 92,
),
child: Text(
'Step 4',
style: GoogleFonts.poppins(
textStyle: TextStyle(
color: Theme.of(context).indicatorColor,
fontSize: 16,
fontWeight: FontWeight.bold,
),
),
),
),
Padding(
padding: const EdgeInsets.only(
left: 97,
),
child: Text(
widget.stepDescription,
style: GoogleFonts.poppins(
textStyle: TextStyle(
color: Theme.of(context).primaryColorLight,
fontSize: 14,
fontWeight: FontWeight.w600,
),
),
),
),
Padding(
padding: const EdgeInsets.only(
left: 35,
top: 25,
),
child: Stack(
children: [
Container(
height: 35,
width: 320,
decoration: BoxDecoration(
color: Theme.of(context).primaryColor,
borderRadius: BorderRadius.circular(20.0),
),
),
Positioned(
left: 10,
top: 14.5,
child: SizedBox(
height: 21,
width: 300,
child: TextField(
controller: searchController,
style: GoogleFonts.poppins(
textStyle: const TextStyle(
color: Colors.white,
fontSize: 14,
fontWeight: FontWeight.bold)),
decoration: InputDecoration(
hintText: 'Search',
hintStyle: GoogleFonts.poppins(
textStyle: TextStyle(
color: Theme.of(context).hintColor,
fontSize: 16,
fontWeight: FontWeight.bold),
),
border: InputBorder.none,
),
),
),
),
Positioned(
left: 320 - 35,
top: 119 - 110,
child: SizedBox(
height: 17,
width: 17,
child: SvgPicture.asset(
'assets/icons/general/search.svg',
color: Theme.of(context).indicatorColor,
),
),
),
],
),
),
Padding(
padding: const EdgeInsets.only(
left: 35,
top: 15,
),
child: Text(
'Popular Choices',
style: GoogleFonts.poppins(
textStyle: const TextStyle(
color: Colors.white,
fontSize: 14,
fontWeight: FontWeight.w600,
),
),
),
),
Padding(
padding: const EdgeInsets.only(
left: 35,
top: 5,
),
child: SizedBox(
height: 370,
width: 320,
child: Center(
child: ListView.builder(
dragStartBehavior: DragStartBehavior.down,
scrollDirection: Axis.vertical,
itemCount: filteredResults.length,
itemBuilder: (context, index) => widget.mealVSWine
? PrefInformationCardWine(
snapShotDocument: filteredResults[index],
cardColor: Theme.of(context).primaryColor,
isSelected:
filteredResults[index] == _selectedSnapshot,
onSelected: () {
setState(() {
_selectedSnapshot = filteredResults[index];
});
},
)
: PrefInformationCardMeal(
snapShotDocument: filteredResults[index],
cardColor: Theme.of(context).primaryColor,
isSelected:
filteredResults[index] == _selectedSnapshot,
onSelected: () {
setState(() {
_selectedSnapshot = filteredResults[index];
});
},
),
),
),
)),
Padding(
padding: const Ed
geInsets.only(
left: 35,
top: 25,
),
child: SubmitSettingChangesButton(
buttonText: 'Continue',
cancelText: 'Cancel',
cancelOnTap: () {
Navigator.pop(context);
},
continueOnTap: () {
_selectedSnapshot != null
? () {
Navigator.pushAndRemoveUntil(
context,
createRoute(FindingRecommendationScreen(
snapshotName: _selectedSnapshot,
)),
(route) => false);
}
: null;
},
),
),
Padding(
padding: const EdgeInsets.only(
top: 15,
left: 171,
),
child: GestureDetector(
onTap: () {
Navigator.pop(context);
},
child: SizedBox(
height: 16,
width: 47,
child: Center(
child: Text(
'Go Back',
style: GoogleFonts.poppins(
textStyle: TextStyle(
color: Theme.of(context).indicatorColor,
fontSize: 11,
fontWeight: FontWeight.bold,
),
),
),
),
),
),
),
],
),
);
}
}
Code Screen 5:
class FindingRecommendationScreen extends StatefulWidget {
const FindingRecommendationScreen({
Key? key,
required this.snapshotName,
}) : super(key: key);
final QueryDocumentSnapshot<Map<String, dynamic>>? snapshotName;
#override
State<FindingRecommendationScreen> createState() =>
_FindingRecommendationScreenState();
}
class _FindingRecommendationScreenState
extends State<FindingRecommendationScreen> {
bool progressDone = true;
late Future<IconData> iconSnapshot;
Future<bool> animationDone() async {
await Future.delayed(const Duration(milliseconds: 3000), () {
setState(() {
progressDone = true;
});
});
return progressDone;
}
Future<IconData> iconData(Future<bool> progress) async {
if (await progress == true) {
return Icons.home;
}
print('function used');
return Icons.done;
}
#override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Theme.of(context).scaffoldBackgroundColor,
body: Column(
children: [
Padding(
padding: const EdgeInsets.symmetric(
horizontal: 35,
vertical: 100,
),
child: Text(
'Your Somellier is searching...',
textAlign: TextAlign.center,
style: GoogleFonts.poppins(
textStyle: TextStyle(
color: Theme.of(context).indicatorColor,
fontSize: 24,
fontWeight: FontWeight.bold,
),
),
),
),
Padding(
padding: EdgeInsets.only(
left: (MediaQuery.of(context).size.width - 200) / 2,
right: (MediaQuery.of(context).size.width - 200) / 2,
top: 50,
),
child: CircularPercentIndicator(
radius: 120,
lineWidth: 4.0,
circularStrokeCap: CircularStrokeCap.round,
animation: true,
animationDuration: 3000,
percent: 1,
// center: FutureBuilder<IconData>(
// future: iconData(animationDone()),
// builder: (context, snapshot) {
// return Icon(
// snapshot.data,
// color: Colors.white,
// );
// },
// ),
// center: const Icon(
// Icons.done_rounded,
// color: Colors.white,
// size: 90,
// ),
center: Text(
'Finding Wine 🍷',
style: GoogleFonts.poppins(
textStyle: const TextStyle(
color: Colors.white,
fontSize: 18,
fontWeight: FontWeight.bold,
),
),
),
progressColor: Theme.of(context).indicatorColor,
),
),
Padding(
padding: const EdgeInsets.only(
left: 35,
right: 35,
top: 200,
),
child: GestureDetector(
onTap: () {
Navigator.pushAndRemoveUntil(
context,
createRoute(const SomellierResultScreen()),
(route) => false);
},
child: Container(
height: 50,
width: MediaQuery.of(context).size.width - 70,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(
25,
),
color: Theme.of(context).primaryColor,
),
child: Center(
child: Text(
widget.snapshotName?['name'],
style: GoogleFonts.poppins(
textStyle: TextStyle(
color: Theme.of(context).indicatorColor,
fontSize: 18,
fontWeight: FontWeight.bold,
),
),
),
),
),
),
),
],
),
);
}
}

Answer 1

Problem
The problem with _selectedSnapshot is that you use it before you ever initialize it with a value.
In your code, you are using
isSelected: filteredResults[index] == _selectedSnapshot,
This causes the error because _selectedSnapshot has no value assigned yet. In your code you assign your value only, when the user taps one of the cards.
onSelected: () {
setState(() {
_selectedSnapshot = filteredResults[index];
});
},
But you never get there, since the screen can't be build because of the error thrown.
Solution
Instead of
late QueryDocumentSnapshot<Map<String, dynamic>> _selectedSnapshot;
use
QueryDocumentSnapshot<Map<String, dynamic>>? _selectedSnapshot = null;
With the ?-Operator you allow your variable _selectedSnapshot to be null.
This means in your context, the user has not yet chosen one option.
You may want to disable the continue button until the user has chosen an option:
continueOnTap: _selectedSnapshot != null ? () {
Navigator.pushAndRemoveUntil(context, createRoute(FindingRecommendationScreen( snapshotName: _selectedSnapshot, )), (route) => false);
} : null,
This checks if _selectedSnapshot is not null. If so the user can continue. Otherwise the Button-Callback is null, which means nothing will happen, if the user presses continue.