firebase - 在Flutter中从Firebase FireCloud接收数据时，不会执行StreamBuilder中的快照代码

Question

我正在尝试从Firecloud数据库获取描述文本，并在3个不同的小部件中使用它们，将这些小部件添加到列表中，然后将该列表传递给ListView。
为此，我在StreamBuilder中执行了以下代码:

StreamBuilder(
              stream: FirebaseFirestore.instance.collection('humansOfLpc').snapshots(),
              builder: (BuildContext context,snapshot){
                if(!snapshot.hasData){
                  return Center(
                    child: Text('Loading...'),
                  );
                }
                print('outside title and desc widget');
                List<TitleAndDescription> titleAndDescriptions=[
                ];
                snapshot.data.docs.map((document){
                    final about = document.data()["about"];
                    final aftercampusProgress =document.data()["afterCampusPlacement"];
                    final incampusPlacement = document.data()["incampusProgress"];
                    print('inside snapshots');
                    print(about);
                    final aboutDesc = TitleAndDescription(
                      title: 'About',
                      description: about,
                    );
                    final incampusProgressDesc = TitleAndDescription(
                      title: 'In-Campus Progress',
                      description: incampusProgress,
                    );
                    final afterCampusPlacementDesc=TitleAndDescription(
                      title: 'After Campus Placements',
                      description: afterCampusPlacement,
                    );
                    titleAndDescriptions.add(aboutDesc);
                    titleAndDescriptions.add(incampusProgressDesc);
                    titleAndDescriptions.add(afterCampusPlacementDesc);

                });

                return Expanded(
                  child: ListView(
                    children: titleAndDescriptions,
                  ),
                );

              },
            ),

我在这里面临的主要问题是它不读取以下代码:

snapshot.data.docs.map((document){
                    final about = document.data()["about"];
                    final aftercampusProgress =document.data()["afterCampusPlacement"];
                    final incampusPlacement = document.data()["incampusProgress"];
                    print('inside snapshots');
                    print(about);
                    final aboutDesc = TitleAndDescription(
                      title: 'About',
                      description: about,
                    );
                    final incampusProgressDesc = TitleAndDescription(
                      title: 'In-Campus Progress',
                      description: incampusProgress,
                    );
                    final afterCampusPlacementDesc=TitleAndDescription(
                      title: 'After Campus Placements',
                      description: afterCampusPlacement,
                    );
                    titleAndDescriptions.add(aboutDesc);
                    titleAndDescriptions.add(incampusProgressDesc);
                    titleAndDescriptions.add(afterCampusPlacementDesc);

                });

我可以这样说，因为控制台正在打印 'outside title and desc widget'，但没有打印 'inside snapshots'。
因此，我的 titleAndDescriptions列表为空，并且我的UI上没有3个小部件以及数据。请告诉我我做错了什么，我有什么选择呢？
提前致谢。

Answer 1

使用forEach而不是map

snapshot.data.docs.forEach((document){
                    final about = document.data()["about"];
                    final aftercampusProgress =document.data()["afterCampusPlacement"];
                    final incampusPlacement = document.data()["incampusProgress"];
                    print('inside snapshots');
                    print(about);
                    final aboutDesc = TitleAndDescription(
                      title: 'About',
                      description: about,
                    );
                    final incampusProgressDesc = TitleAndDescription(
                      title: 'In-Campus Progress',
                      description: incampusProgress,
                    );
                    final afterCampusPlacementDesc=TitleAndDescription(
                      title: 'After Campus Placements',
                      description: afterCampusPlacement,
                    );
                    titleAndDescriptions.add(aboutDesc);
                    titleAndDescriptions.add(incampusProgressDesc);
                    titleAndDescriptions.add(afterCampusPlacementDesc);

                });

在此处查看 Why map doesn't work but forEach does。