Flutter：文本仅在点击按钮两次后更新

Question

我刚开始在 Flutter 中构建一个天气应用程序，我运行遇到了一个问题，即获取用户位置并将其显示为文本小部件需要轻按 2 次 FlatButton。我想做到这一点，以便用户只需点击 FlatButton 位置一次，文本就会更新到他们当前的位置。这是我的代码（我已经删除了不必要的部分 + 样板代码）：

class _ClimaState extends State<Clima> {
  Position position;
  List<Placemark> placemark;
  String location;

  void getLocation() async {
    position = await Geolocator()
        .getCurrentPosition(desiredAccuracy: LocationAccuracy.lowest);
    placemark = await Geolocator()
        .placemarkFromCoordinates(position.latitude, position.longitude);

    location = placemark[0].locality + ", " + placemark[0].country;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: SafeArea(
          child: Padding(
            padding: const EdgeInsets.all(25.0),
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              crossAxisAlignment: CrossAxisAlignment.center,
              children: <Widget>[

                //I've left out the other children for now

                //This is where I want the user's location to be displayed after they tap the location icon
                Text(
                  placemark != null ? location : "Tap the location icon...",
                  style: TextStyle(
                    color: Colors.white,
                    fontSize: 20,
                    fontWeight: FontWeight.w800,

                  ),

                //This is the location icon
                Padding(
                  padding: const EdgeInsets.only(top: 100.0),
                  child: FlatButton(
                    child: Icon(
                      Icons.my_location,
                      color: Colors.white,
                    ),
                    color: Colors.transparent,
                    onPressed: () {
                      setState(() {
                        getLocation();
                      });
                    },
                  ),
                ),
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

Answer 1

我想我通过按你现在的方式调用 set state 解决了你的问题在你重建之前你没有等待你的 Geolocator 数据到 return 这就是为什么需要两次点击才能得到要显示的数据。试试这个设置

  Future<void> getLocation() async {
    position = await Geolocator()
        .getCurrentPosition(desiredAccuracy: LocationAccuracy.lowest);
    placemark = await Geolocator()
        .placemarkFromCoordinates(position.latitude, position.longitude);

    location = placemark[0].locality + ", " + placemark[0].country;
    setState(() {});
  }

//then the onPressed function in your padding widget should be
  onPressed: () async {
              await getLocation();
               },

Flutter：文本仅在点击按钮两次后更新

Flutter: text only updates after button is tapped twice

location

geolocation

dart

flutter