flutter - 小部件状态不会在 iOS 上更新

Question

我正在构建一个记录位置和加速度计数据的应用程序，并将该数据导出到 csv 文件中。

问题：

当我部署到 android 时一切正常。
正如您在构建小部件中看到的那样，我有一个运行时钟： time:DateTime.now().toString()),.
并且位置更新并显示速度信息：speed: (_speed?.round() ?? 0), 。

但是当我部署到 ios 时，小部件的状态根本不会更新。
时钟卡住了，定位服务没有更新。
如果我将特定页面留在主页并再次打开它，时钟会更新到当前时间，但会卡住。
似乎由于某种原因，应用程序的状态在 iOS 中没有更新，我不
知道为什么。

我在 info.plist 中添加了以下几行：

    <key>NSMotionUsageDescription</key>
    <string>banana</string>
    <key>NSLocationAlwaysAndWhenInUseUsageDescription</key>
    <string>banana</string>
    <key>NSLocationAlwaysUsageDescription</key>
    <string>banana</string>
    <key>NSLocationWhenInUseUsageDescription</key>
    <string>banana</string>

编码：

import 'package:flutter/material.dart';
import 'package:different/widgets/StatGridDrive.dart';
import 'package:location/location.dart';
import 'dart:async';
import 'dart:io';
import 'package:path_provider/path_provider.dart';
import 'package:sensors/sensors.dart';

class DataStorage {
  Future<String> get _localPath async {
    final directory = await getApplicationDocumentsDirectory();
    return directory.path;
  }

  Future<File> get _localFile async {
    final path = await _localPath;
    return File('$path/locationData.csv');
  }

  Future<File> writeData(String data) async {
    final file = await _localFile;

    // Write the file
    return file.writeAsString(data, mode: FileMode.append);
  }
}

class DriveScreen extends StatefulWidget {
  final DataStorage data;
  DriveScreen({Key key, @required this.data}) : super(key: key);

  @override
  _DriveScreenState createState() => _DriveScreenState();
}

class _DriveScreenState extends State<DriveScreen> {
  double _speed;
  Timer _timer;
  String _accelerometerValues;
  String _gyroscopeValues;
  List<StreamSubscription<dynamic>> _streamSubscriptions =
      <StreamSubscription<dynamic>>[];

  @override
  void initState() {
    super.initState();
    _streamSubscriptions
        .add(accelerometerEvents.listen((AccelerometerEvent event) {
      setState(() {
        _accelerometerValues = event.x.toString() +
            "," +
            event.y.toString() +
            "," +
            event.z.toString();
      });
    }));
    _streamSubscriptions.add(gyroscopeEvents.listen((GyroscopeEvent event) {
      setState(() {
        _gyroscopeValues = event.x.toString() +
            "," +
            event.y.toString() +
            "," +
            event.z.toString();
      });
    }));
  }

  //location data
  final Location location = Location();

  LocationData _location;
  StreamSubscription<LocationData> _locationSubscription;
  String _error;

  Future<void> _listenLocation() async {
    _locationSubscription =
        location.onLocationChanged.handleError((dynamic err) {
      setState(() {
        _error = err.code;
      });
      _locationSubscription.cancel();
    }).listen((LocationData currentLocation) {
      setState(() {
        _error = null;
        _location = currentLocation;
        _speed = _location.speed;
      });
    });
  }

  Future<void> _stopListen() async {
    _locationSubscription.cancel();
  }

  Future<void> newData() async {
    // Write the variable as a string to the file.
    if (_location != null) {
      widget.data.writeData(
          '${_location.longitude.toString() + "," + _location.latitude.toString() + "," + _accelerometerValues + "," + _gyroscopeValues.toString()} \n');
    }
  }

  @override
  void dispose() {
    super.dispose();
    for (StreamSubscription<dynamic> subscription in _streamSubscriptions) {
      subscription.cancel();
      _locationSubscription.cancel();
      _timer.cancel();
    }
  }

  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
      appBar: AppBar(
          leading: GestureDetector(
            onTap: () {
              _stopListen();
              Navigator.pop(context);
            },
            child: Icon(
              Icons.baby_changing_station,
            ),
          ),
          title: Text('LyftOff'),
          backgroundColor: Color(0xFF282828)),
      backgroundColor: Color(0xFF333333),
      body: SizedBox(
        height: 325,
        child: StatsGrid(
            distance: 15,
            speed: (_speed?.round() ?? 0),
            time: DateTime.now().toString()),
      ),
      floatingActionButton: SizedBox(
        height: 60.0,
        width: 185.0,
        child: FloatingActionButton.extended(
          onPressed: () {
            _listenLocation();
            _timer = new Timer.periodic(
                Duration(milliseconds: 100), (Timer t) => newData());
          },
          backgroundColor: Colors.green,
          label: Text(
            'התחל נסיעה',
            style: TextStyle(
              fontSize: 20.0,
            ),
          ),
          icon: Icon(
            Icons.car_rental,
            size: 30.0,
          ),
          splashColor: Colors.greenAccent,
        ),
      ),
    ));
  }
}

任何指向我做错了什么的指针？

标签： flutter

Answer 1

您在 initstate() 中使用 setstate() 查看更多信息：

[https://stackoverflow.com/questions/53363774/importance-of-calling-setstate-inside-initstate][1]