Textfield filter in Flutter - flutter

Question

I'm a total beginner in Flutter. I try to integrate a textfield filter for my table, but the table is not filtered, but remains unchanged. I added a Provider because I need the current table of Students. after that the Table can't be filtered anymore. Can anyone help me?
here is my code:
class ResultPage extends StatefulWidget {
const ResultPage({Key? key}) : super(key: key);
#override
State<ResultPage> createState() => _ResultPageState();
}
class _ResultPageState extends State<ResultPage> {
List<User>? myData = [];
List<User>? filterData;
_getData(BuildContext context){
myData = Provider.of<LoginService>(context).getStudentsList();
filterData = Provider.of<LoginService>(context).getStudentsList();
}
bool sort = true;
#override
void initState() {
filterData = myData;
super.initState();
}
TextEditingController controller = TextEditingController();
#override
Widget build(BuildContext context) {
_getData(context);
return Scaffold(
body: SingleChildScrollView(
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
SizedBox(
width: double.infinity,
child: Theme(
data: ThemeData.light()
.copyWith(cardColor: Theme.of(context).canvasColor),
child: PaginatedDataTable(
sortColumnIndex: 0,
sortAscending: sort,
header: Container(
padding: const EdgeInsets.all(5),
decoration: BoxDecoration(
border: Border.all(
color: Colors.grey,
),
borderRadius: BorderRadius.circular(12)),
child: TextField(
controller: controller,
decoration: const InputDecoration(
hintText: "Enter name to filter"),
onChanged: (value) {
setState(() {
myData = filterData!
.where(
(element) => element.getName.contains(value))
.toList();
});
},
onSubmitted: (value) {
setState(() {
FocusScope.of(context).unfocus();
});
},
),
),
source: RowSource(
myData: myData,
count: myData!.length,
),
rowsPerPage: 16,
columnSpacing: 8,
columns: const [
DataColumn(
label: Text(
"Schüler",
style: TextStyle(
fontWeight: FontWeight.w600, fontSize: 14),
),
),
DataColumn(
label: Text(
"Anzahl Spiele",
style: TextStyle(
fontWeight: FontWeight.w600, fontSize: 14),
),
),
DataColumn(
label: Text(
"Score",
style: TextStyle(
fontWeight: FontWeight.w600, fontSize: 14),
),
),
],
),
)),
const SizedBox(height: 20),
],
),
)
);
}
}
class RowSource extends DataTableSource {
var myData;
final count;
RowSource({
required this.myData,
required this.count,
});
#override
DataRow? getRow(int index) {
if (index < rowCount) {
return recentFileDataRow(myData![index]);
} else {
return null;
}
}
#override
bool get isRowCountApproximate => false;
#override
int get rowCount => count;
#override
int get selectedRowCount => 0;
}
DataRow recentFileDataRow(User data) {
return DataRow(
cells: [
DataCell(Text(data.getName)),
DataCell(Text(data.getSolvedGames().toString())),
DataCell(Text(data.getScore().toString())),
],
);
}
With my code the table always remains unchanged.