Question

我正在使用video_player软件包。我想加载视频。视频数据是来自API的响应。但是我对NoSuchMethodError: The getter 'value' was called on null. Receiver: null Tried calling: value有错误。我的回答没问题。我print()的回复中有videoURL。问题是我不知道如何在获得响应后添加video_player。我曾尝试这样做，但有错误。

这是我的代码：

class _State extends State<MyApps> {
GlobalKey<PaginatorState> paginatorGlobalKey = GlobalKey();
String videoURL;
VideoPlayerController _videoPlayerController;

@override
  void initState() {
    super.initState();
    playVideo(videoURL);
  }

    @override
      Widget build(BuildContext context) {
        return Scaffold(
           appBar: AppBar(title: Text('My Apps'),
             ),
          body: Paginator.listView(
            key: paginatorGlobalKey,
            pageLoadFuture: sendPagesDataRequest,
            pageItemsGetter: listItemsGetterPages,
            listItemBuilder: listItemBuilder,
            loadingWidgetBuilder: loadingWidgetMaker,
            errorWidgetBuilder: errorWidgetMaker,
            emptyListWidgetBuilder: emptyListWidgetMaker,
            totalItemsGetter: totalPagesGetter,
            pageErrorChecker: pageErrorChecker,
            scrollPhysics: BouncingScrollPhysics(),
          ),
        );
      }

Future<Data> sendPagesDataRequest(int page) async {
 try {
   String url = Uri.encodeFull("APIURL?page=$page");
   http.Response response = await http.get(url);
   Data pagesData = pagesDataFromJson(response.body);
   return pagesData;
  } catch (e) {
 }


void playVideo(dynamic item) async {
 _videoPlayerController = VideoPlayerController.network(item.videoURL)
 ..initialize().then((_) {
 _videoPlayerController.play();
 });
}

Widget listItemBuilder(dynamic item, int index) {
 videoURL= item.videoURL;
  return InkWell(
    child: Card(
     shape: RoundedRectangleBorder(
     borderRadius: BorderRadius.circular(15),
    ),
    elevation: 4,
    margin: EdgeInsets.all(10),
    child: Column(
    children: <Widget>[
     Stack(
      children: <Widget>[
        child: Column(
         crossAxisAlignment: CrossAxisAlignment.stretch,
         children: <Widget>[
           _videoPlayerController.value.initialized
            ? AspectRatio(
             aspectRatio: _videoPlayerController.value.aspectRatio,
             child: VideoPlayer(_videoPlayerController),
            )
           : Container()
            ],
            ),
           ),  
          ],
         ),
        ),
      );
    }

我的代码中有什么错误，我该如何解决？

Answer 1

您应将VideoPlayerController.initialize方法返回的Future存储在State Class变量中：

Future hasInitialized;

void playVideo(dynamic item) async {
 _videoPlayerController = VideoPlayerController.network(item.videoURL);
 hasInitialized = initialize();
 hasInitialized.then((_) {
 _videoPlayerController.play();
 });
}

然后，您可以使用FutureBuilder class构建窗口小部件，具体取决于未来是否完成。

问题是我不知道如何在获得响应后添加video_player。

此小部件可以通过使用connectionState或snapshot.hasData（对于非void Futures）属性来返回Future是否完成的不同事物。

FutureBuilder(
  future: hasInitialized,
  builder: (context, snapshot) {
    if (snapshot.connectionState == ConnectionState.done) {
      // Return here what you want to display.
    } else {
      // Return here what you want to show when the VideoPlayerController is still initializing, like a
      // loading spinner.
      return Center(child: CircularProgressIndicator());
    }
  },
)

有关更多信息，请参见official Cookbook.

如何解决getter'value'在flutter中的null上被调用

1 个答案: