getter 'docs'未为类型"AsyncSnapshot<Object？>"定义

Question

迁移到null安全获取错误后，没有为类型"AsyncSnapshot<对象>'。尝试导入定义"docs"的库，将名称更正为现有getter的名称，或者定义名为"docs"的getter或字段。

错误所在的代码段

return FutureBuilder(
future: searchResultsFuture,
builder: (context, snapshot) {
if (!snapshot.hasData) {
return circularProgress();
}
List<UserResult> searchResults = [];
snapshot.docs.forEach((doc) {    //have error here
User user = User.fromDocument(doc);
UserResult searchResult = UserResult(user);
searchResults.add(searchResult);
});
return ListView(
children: searchResults,
);
},
);
} 

搜索结果未来

handleSearch(String query) {
Future<QuerySnapshot> users =
usersRef.where("displayName", isGreaterThanOrEqualTo: query).get();
setState(() {
searchResultsFuture = users;
});
}
clearSearch() {
searchController.clear();
}

Answer 1

代码中的snapshot是一个AsyncSnapshot，它实际上没有docs子级。要从Firestore获取文档，您需要使用：

snapshot.data.docs

另请参阅FlutterFire关于监听实时数据的文档，其中包含一个显示这一点的示例，我在这里的回答解释了所有快照类型：Firebase中现有类型的快照之间有什么区别？

Answer 2

更改如下：

return FutureBuilder(
future: searchResultsFuture,
builder: (context, **AsyncSnapshot** snapshot) {
if (!snapshot.hasData) {
return circularProgress();
}
List<UserResult> searchResults = [];
**snapshot.data!.docs.forEach((doc) {** 
User user = User.fromDocument(doc);
UserResult searchResult = UserResult(user);
searchResults.add(searchResult);
});
return ListView(
children: searchResults,
);
},
);
}

Answer 3

通常，检索数据需要几毫秒，所以我尝试确保在检索数据后执行我的操作

return StreamBuilder<QuerySnapshot>(
stream: Collectionreference
.snapshots(),
builder: (BuildContext context,
AsyncSnapshot<QuerySnapshot> activitySnapshot) {
if (activitySnapshot.hasError) {
return  Center(
child: Text('Something went wrong'),
);
}
if (activitySnapshot.connectionState == ConnectionState.waiting) {
return Center(
child: SpinKitWave(
color: constants.AppMainColor,
itemCount: 5,
size: 40.0,
)));
}
if (!activitySnapshot.hasData || activitySnapshot.data.docs.isEmpty) {
return Center(
child: Text('Nothing to Display here'),
);
}
if (activitySnapshot.hasData) {
activitySnapshot.data.docs.forEach(doc=>{
print(doc);
})
}
}
});