Having issue while changing values in pie chart flutter - flutter

Question

I tried this code and its working fine for the first time.
double a = 2, b = 3, c = 5;
var color;
Map<String, double> dataMap = Map();
List<Color> colorList = [
Colors.red,
Colors.green,
Colors.yellow,
];
void changeGraph() {
dataMap.putIfAbsent("Fat", () => c);
dataMap.putIfAbsent("Protein", () => b);
dataMap.putIfAbsent("Carbs", () => a);
}
void initState() {
super.initState();
changeGraph();
}
and
PieChart(
dataMap: dataMap,
animationDuration: Duration(milliseconds: 800),
chartLegendSpacing: 32.0,
chartRadius: MediaQuery.of(context).size.width / 2.7,
showChartValuesInPercentage: true,
showChartValues: true,
showChartValuesOutside: false,
chartValueBackgroundColor: Colors.grey[200],
colorList: colorList,
showLegends: true,
legendPosition: LegendPosition.right,
decimalPlaces: 1,
showChartValueLabel: true,
initialAngle: 0,
chartValueStyle: defaultChartValueStyle.copyWith(
color: Colors.blueGrey[900].withOpacity(0.9),
),
chartType: ChartType.disc,
)
then after getting values from user i tried this method for changing the graph
setState(() {
a = newA;
b = newB;
c = newC;
});
also i try to call changeGraph() method but the graph is not changing and its showing the value that it shows first time.
Is there any way to change the values ?

Answer 1

What your'e doing here is changing the values of the variables only and not the values inside the map.The map has the value of a = 2 and not a reference to a.
Meaning that when you say dataMap.putIfAbsent("Carbs", () => a); the value of "Carbs" is not a but it's actually 2 since the value here is an int and not a reference.
In order to change the value of Carbs in the map you need to directly change it from the map itself by doing for example datamap["Carbs"] = newA. Same goes to b and c
Let me know if that doesn't work