All dropdown update when one is updated || flutter || - flutter

Question

I have a code wherein i am using listview.builder to create different dropdown menu items, the problem i am facing is, all the items in different dropdown menu updates when any one is updated.
i have attached my code down below. Your help to fix this would be highly appreciated.
I have also attached a screenshot of what exactly is happening for easier understanding. enter image description here
StreamBuilder<QuerySnapshot>(
stream: FirebaseFirestore.instance
.collection(
'${widget.destination}rates'.toLowerCase())
.snapshots(),
builder: (context, snapshot) {
if (!snapshot.hasData) {
return Text('Loading..');
} else {
List<DropdownMenuItem> tourName = [];
var selectedTour =
List(int.parse(widget.duration) + 1);
for (int i = 0;
i < snapshot.data.docs.length;
i++) {
DocumentSnapshot snap = snapshot.data.docs[i];
tourName.add(
DropdownMenuItem(
child: Text(snap['name']),
value: '${snap['name']}',
),
);
}
return DropdownButton(
items: tourName,
onChanged: (value) {
setState(() {
selectedTour[i] = value;
print(selectedTour);
});
},
value: selectedTour[i],
isExpanded: true,
hint: Text('Select Tour'),
);
}
},
),

Answer 1

You share the same variable selectedTour to all your tiles.
So when you update the selection :
setState(() {
selectedTour = value;
});
It will update everywhere selectedTour is used to display the value selected.
You can either use a new local variable :
} else {
List<DropdownMenuItem> tourName = [];
var selectedTourLocal = null;
for (int i = 0; i < snapshot.data.docs.length; i++)
...
setState(() {
selectedTourLocal = value;
});
...
value: selectedTourLocal,
Or use an array to store the values to the corresponding day.
// declare your array
selectedTour = new List(widget.duration);
...
setState(() {
selectedTour[i] = value;
});
...
value: selectedTour[i],