我知道有很多这样的问题已经在StackOverFlow上浮现了。但是我注意到我的情况非常独特。我正在使用流构建器从Firebase控制台获取有关用户的数据。然后，我使用此快照查询数据并使用它。使我的情况与众不同的是，该错误仅在应用程序在IOS上运行时发生。
流构建器如下，据我所知，检查了所有可能使快照为null的内容:
Widget getPostItem(DocumentSnapshot doc) {
return new FutureBuilder(
future: getOtherUserDoc(doc["uid"]),
builder: (BuildContext context, snapshot) {
List<Widget> children;
if (snapshot.hasData && !snapshot.hasError && snapshot.data["lat"] != null && snapshot.connectionState != ConnectionState.waiting) {
return getCard(doc, snapshot);
} else {
return Center(child: CircularProgressIndicator());
}
});
}
Future<dynamic> getOtherUserDoc(uid) async {
return await Firestore.instance.collection("users").document(uid).get();
}
Widget getCard(doc, snapshot) {
print("getting the value of lat and long");
double useLat = double.parse(snapshot.data["lat"].toString());
double useLong = double.parse(snapshot.data["long"].toString());
double distance = roundDouble(
distanceBetween(widget.lat, widget.long, useLat, useLong) *
0.000621371192,
2);
return Card(
child: SizedBox(
width: MediaQuery.of(context).size.width,
child: new Column(
children: <Widget>[
Expanded(
child: ListTile(
title: new ListView(shrinkWrap: true, children: <Widget>[
new Text(
snapshot.data["nameF"] + ", " + doc["age"],
style: TextStyle(fontSize: 40, color: Colors.red),
),
Row(
children: <Widget>[
Icon(
Icons.location_on,
color: Colors.red,
),
Align(
alignment: Alignment.centerLeft,
child: Text(
snapshot.data["city"] + ", " + snapshot.data["state"],
style: TextStyle(
fontSize: 16,
),
textAlign: TextAlign.left,
),
)
],
),
Text(
distance.toString() + " miles away",
style: TextStyle(
fontSize: 16,
),
textAlign: TextAlign.left,
),
Padding(
padding: EdgeInsets.fromLTRB(0, 5, 0, 5),
child: new Container(
width: double.infinity,
height: 1,
color: Colors.grey,
),
),
new Text(
"Bio:",
style: TextStyle(fontSize: 32, color: Colors.red),
),
Container(
width: MediaQuery.of(context).size.width,
decoration: BoxDecoration(
border: Border.all(
color: Colors.red,
),
borderRadius: BorderRadius.all(Radius.circular(20))),
child: Padding(
padding: EdgeInsets.fromLTRB(5, 5, 5, 5),
child: new Text(
doc["bio"],
style: TextStyle(fontSize: 26),
),
),
),
Padding(
padding: EdgeInsets.fromLTRB(5, 5, 5, 5),
child: Align(
alignment: Alignment.centerLeft,
child: Text(
"Interests: ",
style: TextStyle(
fontSize: 22,
color: Colors.red,
),
textAlign: TextAlign.left,
),
),
),
getInterestGridView(snapshot.data),
]),
),
),
new Padding(
padding: EdgeInsets.fromLTRB(0, 0, 0, 0),
child: Align(
alignment: Alignment.topLeft,
child: Column(
children: <Widget>[
Padding(
padding: EdgeInsets.fromLTRB(0, 0, 0, 0),
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
SizedBox(
width: MediaQuery.of(context).size.width / 2 - 4,
height: MediaQuery.of(context).size.width / 5,
child: Container(
color: Colors.red,
child: SizedBox(
width:
MediaQuery.of(context).size.width / 2 - 4,
height: MediaQuery.of(context).size.width / 5,
child: IconButton(
icon: Icon(
Icons.clear,
size:
MediaQuery.of(context).size.width / 6,
),
color: Colors.black,
onPressed: () {
rejectProfile(doc);
}),
),
),
),
SizedBox(
width: MediaQuery.of(context).size.width / 2 - 4,
height: MediaQuery.of(context).size.width / 5,
child: FlatButton(
child: Image.asset("assets/blindlogo.png"),
color: Colors.black,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(0.0),
side: BorderSide(color: Colors.black)),
onPressed: () {
acceptProfile(doc);
}),
),
],
),
),
],
),
),
),
],
),
),
);
}
最佳答案
snapshot.connectionState != ConnectionState.waiting也为ConnectionState.none都返回true，因此请尝试if(snapshot.connectionState == ConnectionState.waiting)return yourLoadingWIdget; else .... your code;
关于firebase - 方法[]仅在IOS上空调用，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/64309949/