指示在Datatable Flutter上选择的项数的文本

import 'package:flutter/material.dart';

class MyDataTable extends StatefulWidget {
  @override
  _MyDataTableState createState() => _MyDataTableState();
}

class _MyDataTableState extends State<MyDataTable> {
  int selectedItemCount = 0;

  void onItemSelectionChanged(bool selected) {
    setState(() {
      if (selected) {
        selectedItemCount++;
      } else {
        selectedItemCount--;
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return DataTable(
      columns: const <DataColumn>[
        DataColumn(
          label: Text('Name'),
        ),
        DataColumn(
          label: Text('Age'),
        ),
      ],
      rows: <DataRow>[
        DataRow(
          cells: <DataCell>[
            DataCell(Text('John')),
            DataCell(Text('25')),
          ],
          selected: false,
          onSelectChanged: onItemSelectionChanged,
        ),
        DataRow(
          cells: <DataCell>[
            DataCell(Text('Jane')),
            DataCell(Text('30')),
          ],
          selected: false,
          onSelectChanged: onItemSelectionChanged,
        ),
        // Add more rows...
      ],
      // Other DataTable properties...
    );
  }
}

AppBar(
  title: Text('Selected Items: $selectedItemCount'),
  // Other AppBar properties...
)