Flutter Prevent FutureBuilder from running twice - flutter

Question

I am using FutureBuilder in flutter to fill up a drop down menu DropdownButtonFormField, i have the method
onChanged: (String? newValue) {
setState(() {
dropdownBrokers = newValue!;
});
},
Which allows the widget to rebuild and then assign the new value selected from the dropdown list. However, i am now experiencing a problem from my research stating that whenever the setState() is called, the future builder runs again, which makes my dropdown menu populate again. This is the full code snippet
FutureBuilder <List<Broker>>(
future: brokerData,
builder: (context, snapshot){
if(snapshot.hasData){
//do what needs to be done here
List<Broker>? data = snapshot.data;
for(var i = 0; i< data!.length; i++){
_brokers.add(data[i].firmName);
print(data[i].firmName);
}
return Container(
padding: EdgeInsets.all(10),
child: InputDecorator(
decoration: InputDecoration(
labelStyle: TextStyle(
color: Colors.grey
),
isDense: true,
contentPadding: EdgeInsets.all(7.0),
errorStyle: TextStyle(color: Colors.redAccent, fontSize: 16.0),
hintText: 'Select Broker',
border: OutlineInputBorder(borderRadius: BorderRadius.circular(5.0))),
child: DropdownButtonHideUnderline(
child: DropdownButtonFormField<String>(
alignment: Alignment.center,
value: dropdownBrokers,
icon: const Icon(Icons.arrow_downward),
iconSize: 24,
elevation: 16,
style: const TextStyle(color: Colors.indigo),
onChanged: (String? newValue) {
setState(() {
dropdownBrokers = newValue!;
});
},
items: _brokers.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);
}).toList(),
),
),
),
),
);
Also i get an error when i reselect an item.
How do i prevent the FutureBuilder from running twice

Answer 1

FutureBuilder will always be rendered once unless recreated in the build method. So the solution to this can be done in two ways:
1: Only calling brokerData in the FutureBuilder method or
2: Only calling brokerData in the initState override.
You can not do both.
And I assume the data to be populated in the dropdown comes from the future builder. Then use snapshot.data of the future instead of an already created value in this case:
items: _brokers.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);
Change to:
items: snapshot.data.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);