Flutter: Update children state from change in parent - flutter

Question

NOTE: The code may seem very long, but for this question you don't need to understand every part of it.
I have an app, which gets data from an API to build a chart with it. I use the Syncfusion cartesian chart package. This is an economic indicator, so it brings a date and a value, for example:
[[2015 Oct, 0.24],[2015 Nov, 0.26],[2015 Dec, 0.32],[2016 Jan, 0.35],[2016 Feb, 0.40],[2016 Mar, 0.48]]
So, once the data arrives (It has a loading screen for waiting the data form the HTTP request), I build the chart with it.
So in this case, my Parent widget is named ChartScreen. Here's the code:
class ChartScreen extends StatefulWidget {
#override
State<ChartScreen> createState() => _ChartScreenState();
}
class _ChartScreenState extends State<ChartScreen> {
String dropdownValue = '';
initState() {
dropdownValue = '2016';
return super.initState();
}
#override
Widget build(BuildContext context) {
final enterpriseProvider = Provider.of<EnterpriseProvider>(context);
final resp = enterpriseProvider.indicator;
List<IpcData> data = _createIpcList(resp, dropdownValue);
if( data.length == 0 ) {
return Scaffold(
appBar: AppBar(
title: Text('Obteniendo datos...'),
),
body: Container(
color: Colors.black,
width: double.infinity,
height: double.infinity,
child: Center(
child: CircularProgressIndicator(),
),
),
);
}
return
Scaffold(
appBar: AppBar(
title: Text('IPC'),
actions:[
Padding(
padding: const EdgeInsets.all(8.0),
child: DropdownButton(
value: dropdownValue,
icon: const Icon(Icons.arrow_downward),
iconSize: 24,
elevation: 16,
style: const TextStyle(color: Colors.white),
underline: Container(
height: 2,
color: Colors.white,
),
onChanged: (String? newValue) {
dropdownValue = newValue!;
data = _createIpcList(resp, dropdownValue);
setState(() {});
},
items: <String>['2016', '2017', '2018', '2019']
.map<DropdownMenuItem<String>>((String value) {
return DropdownMenuItem<String>(
value: value,
child: Text(value),
);
}).toList()
),
)
]
),
drawer: SideMenu(),
body: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Expanded(
child: Container(
child: ResultChart( formattedData: data )###############################
),
),
],
)
);
}
_createIpcList(List<List<dynamic>> resp, [String? year]) {
print('EL AÑOO');
print(year);
List<IpcData>finalList = [];
if(resp.length != 0) {
for(int i = 0; i < resp.length; i++) {
try {
resp[i][0] = DateFormat.yMMM().format(DateTime.parse(resp[i][0]));
} catch(e) {}
}
}
List<IpcData> ipcList = resp.map((e) => IpcData(e[0], e[1])).toList();
if (year!= null) {
for(int i = 0; i < ipcList.length; i++){
if (ipcList[i].date.contains(year)){
finalList.add(ipcList[i]);
}
}
}
return finalList;
}
}
With the _createIpcList I format the JSON data, so the chart can use it. I highlighted the line in which I call the child whose state I want to update. But before that, you can se that I added a dropdown menu, to select a year from a (hardcoded) list. When the dropdown menu selected item changes (see onChanged), I call the SetState and pass the 'year parameter' to the _createIpcList, which filters the data and returns the items that belong to the selected year. Here's the child code:
class ResultChart extends StatefulWidget {
final List<IpcData> formattedData;
const ResultChart({
Key? key,
required this.formattedData
}) : super(key: key);
#override
_ResultChartState createState() => _ResultChartState();
}
class _ResultChartState extends State<ResultChart> {
late List<IpcData> _chartData;
#override
void initState() {
_chartData = widget.formattedData;
super.initState();
}
#override
Widget build(BuildContext context) {
return Container(
child: SfCartesianChart(
backgroundColor: Colors.black,
enableAxisAnimation: false,
trackballBehavior: TrackballBehavior(
enable: true,
shouldAlwaysShow: true,
tooltipSettings: InteractiveTooltip(
borderWidth: 2,
borderColor: Colors.grey,
color: Colors.grey[400],
format: 'point.x : point.y'
)
),
zoomPanBehavior: ZoomPanBehavior(
enablePanning: true,
enablePinching: true,
enableDoubleTapZooming: true,
zoomMode: ZoomMode.xy,
),
primaryXAxis: CategoryAxis(
labelRotation: 90,
labelStyle: TextStyle(
fontWeight: FontWeight.bold,
color: Colors.grey[400]
),
axisLine: AxisLine(
width: 2,
color: Colors.grey
),
majorGridLines: MajorGridLines(width: 1),
),
primaryYAxis: NumericAxis(
labelStyle: TextStyle(
fontWeight: FontWeight.bold,
color: Colors.grey[400]
),
axisLine: AxisLine(
width: 2,
color: Colors.grey
),
title: AxisTitle( text: 'IPC', textStyle: TextStyle(fontSize: 20, fontWeight: FontWeight.bold)),
majorGridLines: MajorGridLines(width: 1),
),
series: <ChartSeries>[
LineSeries<IpcData, String>(
color: Colors.blue,
dataSource: _chartData,
xValueMapper: (IpcData data, _) => data.date,
yValueMapper: (IpcData data, _) => data.value
)
],)
);
}
}
class IpcData {
final String date;
final double value;
IpcData(this.date, this.value);
}
My problem is that, no matter which year I select, the chart doesn't change. I know that the 'dropdownValue' changes because I debugged with some prints() but I don´t know how to rebuild or set state of the ResultChart widget.

Answer 1

Well it turn out that I continued debugging, and actually the ResultChart widget was being rebuilt again and again, but I never called the setState function inside the children. Beginner error I know, but I'm new with Flutter.