我想将SFDataGrid导出为PDF，包括StackedHeader和Footer，但它始终为空。下面的示例代码

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:syncfusion_flutter_datagrid/datagrid.dart';
import 'package:syncfusion_flutter_pdf/pdf.dart' as sf_pdf;
import 'package:syncfusion_flutter_datagrid_export/export.dart';
import 'package:printing/printing.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatefulWidget {
  const MyApp({super.key});

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    List<Employee> employees = [
      Employee(10001, 'James', 'Project Lead', 20000),
      Employee(10002, 'Kathryn', 'Manager', 30000),
      Employee(10003, 'Lara', 'Developer', 15000),
      Employee(10004, 'Michael', 'Designer', 15000),
      Employee(10005, 'Martin', 'Developer', 15000),
      Employee(10006, 'Newberry', 'Developer', 15000),
      Employee(10007, 'Balnc', 'Developer', 15000),
      Employee(10008, 'Perry', 'Developer', 15000),
      Employee(10009, 'Gable', 'Developer', 15000),
      Employee(10010, 'Grimes', 'Developer', 15000)
    ];

    GlobalKey<SfDataGridState> key = GlobalKey<SfDataGridState>();
    EmployeeDataSource employeeDataSource =
        EmployeeDataSource(employees: employees);
    void exportDataGridToPDF() async {
      sf_pdf.PdfDocument document = key.currentState!.exportToPdfDocument();
      final List<int> bytes = document.saveSync();

      await Printing.layoutPdf(onLayout: (_) => Uint8List.fromList(bytes));
      document.dispose();
    }

    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
        body: Column(
          children: [
            SfDataGrid(
              key: key,
              source: employeeDataSource,
              stackedHeaderRows: [
                StackedHeaderRow(
                  cells: [
                    StackedHeaderCell(
                      columnNames: ['id', 'name', 'designation', 'salary'],
                      child: const Text("Stacked Header"),
                    ),
                  ],
                ),
              ],
              footer: const Text("FOOTER"),
              columns: [
                GridColumn(
                    columnName: 'id',
                    label: Container(
                        padding: const EdgeInsets.symmetric(horizontal: 16.0),
                        alignment: Alignment.centerRight,
                        child: const Text(
                          'ID',
                          overflow: TextOverflow.ellipsis,
                        ))),
                GridColumn(
                    columnName: 'name',
                    label: Container(
                        padding: const EdgeInsets.symmetric(horizontal: 16.0),
                        alignment: Alignment.centerLeft,
                        child: const Text(
                          'Name',
                          overflow: TextOverflow.ellipsis,
                        ))),
                GridColumn(
                    columnName: 'designation',
                    label: Container(
                        padding: const EdgeInsets.symmetric(horizontal: 16.0),
                        alignment: Alignment.centerLeft,
                        child: const Text(
                          'Designation',
                          overflow: TextOverflow.ellipsis,
                        ))),
                GridColumn(
                    columnName: 'salary',
                    label: Container(
                        padding: const EdgeInsets.symmetric(horizontal: 16.0),
                        alignment: Alignment.centerRight,
                        child: const Text(
                          'Salary',
                          overflow: TextOverflow.ellipsis,
                        ))),
              ],
            ),
            ElevatedButton(
                onPressed: () => exportDataGridToPDF(),
                child: const Text("Export to PDF"))
          ],
        ),
      ),
    );
  }
}

class Employee {
  Employee(this.id, this.name, this.designation, this.salary);
  final int id;
  final String name;
  final String designation;
  final int salary;
}

class EmployeeDataSource extends DataGridSource {
  EmployeeDataSource({required List<Employee> employees}) {
    dataGridRows = employees
        .map<DataGridRow>((dataGridRow) => DataGridRow(cells: [
              DataGridCell<int>(columnName: 'id', value: dataGridRow.id),
              DataGridCell<String>(columnName: 'name', value: dataGridRow.name),
              DataGridCell<String>(
                  columnName: 'designation', value: dataGridRow.designation),
              DataGridCell<int>(
                  columnName: 'salary', value: dataGridRow.salary),
            ]))
        .toList();
  }

  List<DataGridRow> dataGridRows = [];

  @override
  List<DataGridRow> get rows => dataGridRows;

  @override
  DataGridRowAdapter? buildRow(DataGridRow row) {
    return DataGridRowAdapter(
        cells: row.getCells().map<Widget>((dataGridCell) {
      return Container(
          alignment: (dataGridCell.columnName == 'id' ||
                  dataGridCell.columnName == 'salary')
              ? Alignment.centerRight
              : Alignment.centerLeft,
          padding: const EdgeInsets.symmetric(horizontal: 16.0),
          child: Text(
            dataGridCell.value.toString(),
            overflow: TextOverflow.ellipsis,
          ));
    }).toList());
  }
}

输出x1c 0d1x
我的另一个选择是使用DataGridToPdfConverter-DataGridPdfHeaderFooterExportCallback创建一个自定义页脚，但我找不到如何在输出中获得数据表底部的位置。基本上，我想在数据表下面创建一个页脚。