Fixing Issues with FutureBuilder - flutter

Question

In my Flutter project, I am trying to implement a button click event by using FutureBuilder. Basically when the button clicked, it supposed to get the data and display in a table. So my button onPressed event handling is as below:
onPressed: () async{
if (_formKey.currentState.validate()) {
_formKey.currentState.save();
var p = double.parse(loanAmount);
var r = double.parse(interestRate);
var n = int.parse(monthes);
Api api = new Api();
new FutureBuilder<List>(
future: api.calculateEmi(p, r, n),
builder: (BuildContext buildContext, AsyncSnapshot<List> snapshot) {
if (!snapshot.hasData) {
return Center(child: CircularProgressIndicator());
} else {
print( snapshot.data);
return new SingleChildScrollView(
padding: const EdgeInsets.all(8.0),
child: DataTableWidget(listOfColumns: snapshot.data.map(
(e)=>{
'Month': e['Month'],
'Principal': e['Principal'],
'InterestP': e['InterestP'],
'PrinciplaP': e['PrinciplaP'],
'RemainP': e['RemainP']
}).toList()
),
);
}
}
);
}
}
The Api call is working and the method calculateEmi is called and get data returned ( a List of Map), but the view just not updated and no table appeared at all, and I use breakpoint at the builder portion but it never go into it, where did I do wrong, can anyone help? thanks.

Answer 1

The FutureBuilder needs to be inserted somewhere in the flutter widget tree. Simply creating a new FutureBuilder doesn't tell flutter what to do with it.
I'm guessing you instead want to put the FutureBuilder you created somewhere in the parent widget of the onPressed method. If you need it to only show when the button is pressed you can do that with a bool that determines whether to show the FutureBuilder or not.
Ex.
Widget build(context) {
if(buttonPressed) {
return FutureBuilder(
...
);
}
else {
return Container();
}
}