FutureBuilder 块空问题答案

【问题标题】：FutureBuilder block null issueFutureBuilder 块空问题
【发布时间】：2021-11-23 05:14:54
【问题描述】：

错误：正文可能正常完成，导致返回“null”，但返回类型可能是不可为空的类型。尝试在末尾添加 return 或 throw 语句。

我收到 FutureBuilder 行的此错误，但我找不到解决方法。问题是我不能在这里解决问题。

任何帮助将不胜感激

Widget build(BuildContext context) => Scaffold(
        body: FutureBuilder<Article>(
          future: _futureArticle,
          builder: (BuildContext context, AsyncSnapshot<Article> snapshot) {
            if (snapshot.hasData) {
              final article = snapshot.data?.data;
              CustomScrollView(
                slivers: [
                  SliverAppBar(
                    // backgroundColor: Colors.red,
                    expandedHeight: 200,
                    floating: true,
                    pinned: true,
                    flexibleSpace: FlexibleSpaceBar(
                      background: Image.network(article == null
                          ? 'https://www.tonymacx86.com/attachments/2019-02-05-07-50-43-jpeg.385401/'
                          : article.imageUrl!),
                      title: Text('${article!.title}'),
                      centerTitle: true,
                    ),
                    leading: const Icon(Icons.arrow_back),
                    actions: const [
                      Icon(Icons.settings),
                      SizedBox(width: 12),
                    ],
                  ),
                  buildImages(),
                ],
              );
            }
            
            
          },
          
        ),
      );

  Widget buildImages() => SliverToBoxAdapter(
        child: Card(
          elevation: 4.0,
          shape: RoundedRectangleBorder(
            borderRadius: BorderRadius.circular(10.0),
          ),
          child: ListTile(
            // leading: Image.network(article.imageUrl),
            title: Text(
              'Title: ',
            ),
            subtitle: Text(
              'Content: ',
            ),
          ),
        ),
      );
}

【问题讨论】：

标签： flutter dart

【解决方案1】：

您必须 return 构建器函数中的小部件。

Widget build(BuildContext context) => Scaffold(
        body: FutureBuilder<Article>(
          future: _futureArticle,
          builder: (BuildContext context, AsyncSnapshot<Article> snapshot) {
            if (snapshot.hasData) {
              final article = snapshot.data?.data;
           return   CustomScrollView(
                slivers: [
                  SliverAppBar(
                    // backgroundColor: Colors.red,
                    expandedHeight: 200,
                    floating: true,
                    pinned: true,
                    flexibleSpace: FlexibleSpaceBar(
                      background: Image.network(article == null
                          ? 'https://www.tonymacx86.com/attachments/2019-02-05-07-50-43-jpeg.385401/'
                          : article.imageUrl!),
                      title: Text('${article!.title}'),
                      centerTitle: true,
                    ),
                    leading: const Icon(Icons.arrow_back),
                    actions: const [
                      Icon(Icons.settings),
                      SizedBox(width: 12),
                    ],
                  ),
                  buildImages(),
                ],
              );
            }
            
            
          },
          
        ),
      );

即使snapshot.hasData 是false，你也必须返回一些东西。

【讨论】：