Flutter应用程序:方向生成器的更改导致流具有等待而不是活动的ConnectionState

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Orientation Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: OrientationPage(),
    );
  }
}

class OrientationPage extends StatefulWidget {
  @override
  _OrientationPageState createState() => _OrientationPageState();
}

class _OrientationPageState extends State<OrientationPage> {
  Stream<DeviceOrientation> _orientationStream;
  DeviceOrientation _currentOrientation;

  @override
  void initState() {
    super.initState();
    _orientationStream = _getOrientationStream();
  }

  Stream<DeviceOrientation> _getOrientationStream() {
    return Stream<DeviceOrientation>.periodic(Duration(milliseconds: 200), (_) {
      return MediaQuery.of(context).orientation;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Orientation Demo'),
      ),
      body: Center(
        child: StreamBuilder<DeviceOrientation>(
          stream: _orientationStream,
          builder: (context, snapshot) {
            if (snapshot.connectionState == ConnectionState.waiting) {
              return CircularProgressIndicator();
            } else if (snapshot.connectionState == ConnectionState.active) {
              _currentOrientation = snapshot.data;
              return Text('Current Orientation: $_currentOrientation');
            } else {
              return Text('Orientation Stream Ended');
            }
          },
        ),
      ),
    );
  }
}