ListView 不会将对象与文档分开

Question

我正在尝试创建可滚动的帖子列表，但我得到的是静态不可滚动的字符串块，它正在溢出。

示例：

溢出：

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        floatingActionButton: FloatingActionButton(
          onPressed: _writePost,
          tooltip: 'Increment',
          child: Icon(Icons.create, color: Colors.grey[300]),
        ),
        body: SizedBox(
            child: Container(
                child: Column(children: [
          StreamBuilder<List<Post>>(
            initialData: const [],
            stream: _socketStream.stream,
            builder: (context, snapshot) {
              if (_isLoading) {
                return const Center(
                  child: CircularProgressIndicator(),
                );
              }
               ListView(
                scrollDirection: Axis.vertical,
                shrinkWrap: true,
                children: [
                  ...snapshot.data!.map<Widget>(
                    (post) => Padding(
                      key: ValueKey(post.id),
                      padding: const EdgeInsets.symmetric(vertical: 10),
                      child: ListTile(
                        title: Text(
                          post.content,
                          style: const TextStyle(fontSize: 20),
                        ),
                        trailing: MaterialButton(
                          onPressed: () {
                            _deletePost(post.id);
                          },
                          child: const Icon(
                            Icons.delete,
                            size: 30,
                          ),
                        ),
                      ),
                    ),
                  )
                ],
              );
            },
          ),
        ]))));
  }

而且，它们都像一张卡片一样，没有分开。

编辑后的代码，滚动但不分隔帖子

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        floatingActionButton: FloatingActionButton(
          onPressed: _writePost,
          tooltip: 'Increment',
          child: Icon(Icons.create, color: Colors.grey[300]),
        ),
        body: SizedBox(
          height: 500, 
          child:
              StreamBuilder<List<Post>>(
            initialData: const [],
            stream: _socketStream.stream,
            builder: (context, snapshot) {
              if (_isLoading) {
                return const Center(
                  child: CircularProgressIndicator(),
                );
              }
              return Card(child: ListView(
                scrollDirection: Axis.vertical,
                shrinkWrap: true,
                children: [
                  ...snapshot.data!.map<Widget>(
                    (post) => Padding(
                      key: ValueKey(post.id),
                      padding: const EdgeInsets.symmetric(vertical: 10),
                      child: ListTile(
                        title: Text(
                          post.content,
                          style: const TextStyle(fontSize: 20),
                        ),
                        trailing: MaterialButton(
                          onPressed: () {
                            _deletePost(post.id);
                          },
                          child: const Icon(
                            Icons.delete,
                            size: 30,
                          ),
                        ),
                      ),
                    ),
                  )
                ],
               ) );
            },
          ),
        ));
  }

我试图找出文档中的错误，但是...

Answer 1

@override
  Widget build(BuildContext context) {
    return Scaffold(
        floatingActionButton: FloatingActionButton(
          onPressed: _writePost,
          tooltip: 'Increment',
          child: Icon(Icons.create, color: Colors.grey[300]),
        ),
        body: SizedBox(
           height: MediaQuery.of(context).height*0.8,  // add this line 
            child: 
          // Container(        // do not need this
          //                   child:   // and this do not need    
          // Column(children: [      // and this do not need 
          StreamBuilder<List<Post>>(
            initialData: const [],
            stream: _socketStream.stream,
            builder: (context, snapshot) {
              if (_isLoading) {
                return const Center(
                  child: CircularProgressIndicator(),
                );
              }
               ListView(  // change this to ListView.builder for more performance
                scrollDirection: Axis.vertical,
                shrinkWrap: true,
                children: [
                  ...snapshot.data!.map<Widget>(
                    (post) => Padding(
                      key: ValueKey(post.id),
                      padding: const EdgeInsets.symmetric(vertical: 10),
                      child: ListTile(
                        title: Text(
                          post.content,
                          style: const TextStyle(fontSize: 20),
                        ),
                        trailing: MaterialButton(
                          onPressed: () {
                            _deletePost(post.id);
                          },
                          child: const Icon(
                            Icons.delete,
                            size: 30,
                          ),
                        ),
                      ),
                    ),
                  )
                ],
              );## Heading ##
            },
          ),
       // ]) // comment this
       // ).  // and comment this
     )
   );
  }

Answer 2

Column和Listview取最大可用高度。因此，这里是 Column 的子项的 Listview 的高度应该受到限制。您可以通过将 ListView 包装在 Expanded:

中来实现

child: Column(
        children: [
          Expanded(
            child: ListView(

此外，如果您的列表很长，不建议将 shrinkwrap 设置为 true。因为它使 ListView 在构建布局时加载其所有项目。所以它会降低性能。

ListView 不会将对象与文档分开

ListView doesn't separate objects from doc

flutter

user-interface

listview