从Firestore到Flutter的流生成器

这应该适用于一项

  body: new StreamBuilder(    stream: Firestore.instance.collection("collection").snapshots(),    builder: (context, snapshot) {      if (!snapshot.hasData) {        return Text(          'No Data...',        );      } else {<documentSnapshot> items = snapshot.data.documents;          return new Lost_Card(          headImageAssetPath : items[0]["url"]          );      }

如果要从许多文档中创建列表生成器，请像这样使用它

        return new ListView.builder( itemCount: snapshot.data.documents.length, itemBuilder: (context, index) {   documentSnapshot ds = snapshot.data.documents[index];   return new Lost_Card(     headImageAssetPath : ds["url"];);