flutter写一个时间选择器

以下是Flutter中的时间选择器示例代码：

import 'package:flutter/material.dart';

class TimePickerDemo extends StatefulWidget {
  @override
  _TimePickerDemoState createState() => _TimePickerDemoState();
}

class _TimePickerDemoState extends State<TimePickerDemo> {
  TimeOfDay _time = TimeOfDay.now();

  Future<void> _selectTime(BuildContext context) async {
    final TimeOfDay? newTime =
        await showTimePicker(context: context, initialTime: _time);
    if (newTime != null) {
      setState(() {
        _time = newTime;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Time Picker Demo'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'Selected Time:',
              style: TextStyle(fontSize: 20),
            ),
            SizedBox(height: 10),
            Text(
              _time.format(context),
              style: TextStyle(fontSize: 40, fontWeight: FontWeight.bold),
            ),
            SizedBox(height: 20),
            ElevatedButton(
              onPressed: () => _selectTime(context),
              child: Text('Select Time'),
            ),
          ],
        ),
      ),
    );
  }
}

上述代码中的`_selectTime()`方法使用`showTimePicker`函数来显示时间选择器，并根据用户选择更新当前选定的时间。`_time.format(context)`方法将选定的时间格式化为可读的文本并显示在屏幕上。在此示例中，我们使用了`ElevatedButton`来显示一个按钮，以便用户可以打开时间选择器并选择时间。