Flutter: Prevent executed feturebuilder when setState is occurred - flutter

Question

I am trying to load DropDownMenu inside Future builder.In my widget i have a Column. Inside Column I have a few widget :
#override
Widget build(BuildContext context) {
return Column(
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
Row(),
Divider(),
Container(),
...widget._detailsModel.data.appletActions.map((item) {
.....
...item.appletInputs.map((inputs) {
FutureBuilder(
future: MyToolsProvider()
.getDropDownConfiges(inputs.dataUrl),
builder:
(ctx,AsyncSnapshot<DropDownModel.DropDownConfigToolsModle>snapshot) {
if (!snapshot.hasData ||
snapshot.connectionState ==
ConnectionState.waiting) {
return Center(
child: CircularProgressIndicator(),
);
}
if (snapshot.hasData &&
snapshot.connectionState ==
ConnectionState.done) {
_dropDown = snapshot.data.data[0];
return DropdownButton<DropDownModel.DataModle>(
hint: Text("Select Item"),
value: _dropDown,
onChanged: (data) {
setState(() {
_dropDown = data;
});
},
items: snapshot.data.data.map((item) {
return DropdownMenuItem<
DropDownModel.DataModle>(
value: item,
child: Row(
children: <Widget>[
Icon(Icons.title),
SizedBox(
width: 10,
),
Text(
item.title,
style: TextStyle(
color: Colors.black),
),
],
),
);
}).toList(),
);
} else {
return Center(
child: Text('failed to load'),
);
}
}),
}
}
]
As you can see i have FutureBuilder inside a loop to show DropdownButton.everything is ok and code works as a charm but my problem is :
onChanged: (data) {
setState(() {
_dropDown = data;
})
every time setState called, future: MyToolsProvider().getDropDownConfiges(inputs.dataUrl), is executed and
_dropDown = snapshot.data.data[0]; again initialized and it get back in a first time .
It is not possible declared MyToolsProvider().getDropDownConfiges(inputs.dataUrl), in initState() method because inputs.dataUrl it is not accessible there.
How can i fixed that?

Answer 1

Updating parent state from within a builder is anti-pattern here. To reduce future errors and conflicts I recommend to wrap the parts that use and update _dropDown variable as a statefull widget.
Afterward the builder is just responsible of selecting correct widget based on future results and separated widget will only update itself based on interactions. Then hopefully many current and potential errors will disappear.

Answer 2

Do one thing, change this
_dropDown = snapshot.data.data[0];
to
_dropDown ??= snapshot.data.data[0];
What this will do is, it will check if _dropDown is null then assign it with value otherwise it won't.