英文:
How can MylocationCountry values appear in the Text() appbar?
问题
我想在应用栏文本中显示MyLocationCountry的值，但数据为空。同时，当我使用print($MyLocationCountry)时，数据是存在的。我想尝试在我的应用栏中显示国家位置数据，但我困惑为什么Mylocationcountry的值不以文本形式显示。
我的代码中的问题是：数据不显示，也许有人可以帮助我？
英文:
I want to display the value of MyLocationCountry in the appbar text, but the data is null. Meanwhile, when I make print($MyLocationCountry) the data is there. I want to try displaying country location data to my appbar and I am confused why the value data on Mylocationcountry does not appear in text form
This my code
`
Class _HomePageState extends State<HomePage> {
int currentIndexPage = 0;
final location = new Location();
String? locationError;
String? MylocationCountry, MylocationCity;
PrayerTimes? prayerTimes;
double? latitude, longitude, pLat, pLong;
@override
void initState() {
getLocationData().then((locationData) async {
if (!mounted) {
return;
}
if (locationData != null) {
setState(() {
prayerTimes = PrayerTimes(
Coordinates(locationData.latitude, locationData.longitude),
DateComponents.from(DateTime.now()),
CalculationMethod.karachi.getParameters());
pLat = prayerTimes!.coordinates.latitude;
pLong = prayerTimes!.coordinates.longitude;
print("Latitude : $pLat, Longitude : $pLong");
});
} else {
setState(() {
locationError = "Couldn't Get Your Location!";
});
}
List<MyLocation.Placemark> placemarks = await MyLocation.placemarkFromCoordinates(pLat!, pLong!);
MylocationCountry = placemarks.reversed.last.country.toString();
MylocationCity = placemarks.reversed.last.locality.toString();
print("Country : $MylocationCountry, City : $MylocationCity");
});
//DateTime.now().hour >= 18 && DateTime.now().hour <= 19
super.initState();
}
@override
Widget build(BuildContext context) {
final country = this.MylocationCountry.toString();
return Scaffold(
appBar: PreferredSize(
preferredSize: Size.fromHeight(225),
child: AppBar(
automaticallyImplyLeading: false,
title: RichText(
text: TextSpan(
text: country,
style: TextStyle(
fontSize: 20,
fontWeight: FontWeight.w500,
),
children:
<TextSpan>[
TextSpan(
text: "\n$MylocationCity",
style: TextStyle(
fontSize: 16,
fontWeight: FontWeight.normal,
),
),
]),),
`
The data is not show when i make the code like this, maybe someone can help me?
答案1
得分: 0
如果你仔细查看代码，你会发现在设置了MylocationCountry的值之后，你没有调用setState。
以下是更新后的代码片段：
setState(() {
List<MyLocation.Placemark> placemarks =
await MyLocation.placemarkFromCoordinates(pLat!, pLong!);
MylocationCountry = placemarks.reversed.last.country.toString();
MylocationCity = placemarks.reversed.last.locality.toString();
});
英文:
If you look at the code carefully, you will see that you are not calling setState after setting the value of MylocationCountry.
Here is an updated code snippet:
setState(() {
List<MyLocation.Placemark> placemarks =
await MyLocation.placemarkFromCoordinates(pLat!, pLong!);
MylocationCountry = placemarks.reversed.last.country.toString();
MylocationCity = placemarks.reversed.last.locality.toString();
});
答案2
得分: 0
我建议您使用FutureBuilder的方法，可能会有所帮助：
class _HomePageState extends State<HomePage> {
...
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: PreferredSize(
preferredSize: Size.fromHeight(225),
child: FutureBuilder(
future: MyLocation.placemarkFromCoordinates(pLat!, pLong!),
builder: (BuildContext context, AsyncSnapshot<List<MyLocation.Placemark>> snapshot) {
if (snapshot.hasData) {
MylocationCountry = snapshot.data!.reversed.last.country.toString();
MylocationCity = snapshot.data!.reversed.last.locality.toString();
}
return AppBar(
automaticallyImplyLeading: false,
title: RichText(
text: TextSpan(
text: MylocationCountry ?? '',
style: TextStyle(
fontSize: 20,
fontWeight: FontWeight.w500,
),
children: <TextSpan>[
TextSpan(
text: "\n${MylocationCity ?? ''}",
style: TextStyle(
fontSize: 16,
fontWeight: FontWeight.normal,
),
),
],
),
),
);
},
),
),
...
);
}
}
英文:
I suggest you a futureBuilder approach that could be helpful:
class _HomePageState extends State<HomePage> {
...
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: PreferredSize(
preferredSize: Size.fromHeight(225),
child: FutureBuilder(
future: MyLocation.placemarkFromCoordinates(pLat!, pLong!),
builder: (BuildContext context, AsyncSnapshot<List<MyLocation.Placemark>> snapshot) {
if (snapshot.hasData) {
MylocationCountry = snapshot.data!.reversed.last.country.toString();
MylocationCity = snapshot.data!.reversed.last.locality.toString();
}
return AppBar(
automaticallyImplyLeading: false,
title: RichText(
text: TextSpan(
text: MylocationCountry ?? '',
style: TextStyle(
fontSize: 20,
fontWeight: FontWeight.w500,
),
children: <TextSpan>[
TextSpan(
text: "\n${MylocationCity ?? ''}",
style: TextStyle(
fontSize: 16,
fontWeight: FontWeight.normal,
),
),
],
),
),
);
},
),
),
...
);
}
}
答案3
得分: 0
MyLocation.placemarkFromCoordinates 是异步的，因此它会有一些延迟，这意味着在地标数据可用之前，您的构建函数会运行。您需要在此调用完成后更新状态。
setState(() {
MylocationCountry = placemarks.reversed.last.country.toString();
MylocationCity = placemarks.reversed.last.locality.toString();
})
英文:
MyLocation.placemarkFromCoordinates is asynchronous so it'll execute with some delay which means your build function runs before placemarks data is available. You need to update state after this call finishes.
setState((){
MylocationCountry = placemarks.reversed.last.country.toString();
MylocationCity = placemarks.reversed.last.locality.toString();
})
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