我会分享一些在网上找不到，或者遇到问题并解决的事情。

最近在调研Flutter视频播放，在横屏切换到竖屏的时候遇到了点问题。代码如下：

class PortraitPage extends StatefulWidget {
  const PortraitPage({Key? key}) : super(key: key);

  @override
  _PortraitPageState createState() => _PortraitPageState();
}

class _PortraitPageState extends State<PortraitPage> {
  VideoPlayerController? controller;

  @override
  void initState() {
    super.initState();
    controller = VideoPlayerController.network(
        "https://cdn-resource.ekwing.com/acpf/data/upload/expand/2017/08/29/59a53da773e00.mp4")
      ..setLooping(true)
      ..initialize().then((_) {
        controller!.play();
      });
  }

  @override
  void dispose() {
    controller!.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Column(
          children: [
            AspectRatio(
              aspectRatio: controller!.value.aspectRatio,
              child: VideoPlayer(controller!),
            ),
            MaterialButton(
                onPressed: () {
                  Navigator.push(
                      context,
                      MaterialPageRoute(builder: (context) => VideoFullPage(controller: controller!)));
                },
                child: Text("切换全屏"))
          ],
        ),
      ),
    );
  }
}

class VideoFullPage extends StatefulWidget {
  final VideoPlayerController controller;

  const VideoFullPage({Key? key, required this.controller}) : super(key: key);

  @override
  _VideoFullPageState createState() => _VideoFullPageState();
}

class _VideoFullPageState extends State<VideoFullPage> {

  @override
  void initState() {
    super.initState();
    SystemChrome.setPreferredOrientations([
      DeviceOrientation.landscapeLeft,
    ]);
  }

  @override
  void dispose() {
  ///页面退出时，切换为竖屏
    SystemChrome.setPreferredOrientations([
      DeviceOrientation.portraitUp,
    ]);
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
          home: Scaffold(
            backgroundColor: Colors.black,
            body: Stack(
              children: [
                Center(
                  child: AspectRatio(
                    aspectRatio: widget.controller.value.aspectRatio,
                    child: VideoPlayer(widget.controller),
                  ),
                ),
                Padding(
                  padding: const EdgeInsets.only(top: 25, right: 20),
                  child: IconButton(
                    icon: const Icon(Icons.arrow_back_ios),
                    color: Colors.white,
                    onPressed: () {
                    ///点击返回，先切换竖屏，然后退出页面
                      SystemChrome.setPreferredOrientations([
                        DeviceOrientation.portraitUp,
                      ]);
                      Navigator.pop(context);
                    },
                  ),
                )
              ],
            ),
          ),
        );
  }
}

从竖屏切换到全屏没有问题，点击物理按键:Back，会出现先退出了页面，然后再切换到竖屏。体验效果不是很好，所以修改方案：

1. 拦截返回按键。
2. 先切换为竖屏，然后Navigator.pop(context)。

class _VideoFullPageState extends State<VideoFullPage> {
  @override
  void initState() {
    super.initState();
    SystemChrome.setPreferredOrientations([
      DeviceOrientation.landscapeLeft,
    ]);
  }

  @override
  Widget build(BuildContext context) {
    return WillPopScope(
        child: MaterialApp(
          home: Scaffold(
            backgroundColor: Colors.black,
            body: Stack(
              children: [
                Center(
                  child: Hero(
                    tag: "player",
                    child: AspectRatio(
                      aspectRatio: widget.controller.value.aspectRatio,
                      child: VideoPlayer(widget.controller),
                    ),
                  ),
                ),
                Padding(
                  padding: const EdgeInsets.only(top: 25, right: 20),
                  child: IconButton(
                    icon: const Icon(Icons.arrow_back_ios),
                    color: Colors.white,
                    onPressed: () {
                      SystemChrome.setPreferredOrientations([
                        DeviceOrientation.portraitUp,
                      ]);
                      Navigator.pop(context);
                    },
                  ),
                )
              ],
            ),
          ),
        ),
        onWillPop: () async {
          SystemChrome.setPreferredOrientations([
            DeviceOrientation.portraitUp,
          ]);
          Navigator.pop(context);
          return false;
        });
  }
}

完整代码见GitHub