API 密钥在 Flutter Weather API 应用程序（Android）中不起作用

Question

我正在学习 Flutter 并尝试构建一个 Android 应用程序。基本上是一个天气应用程序，它从站点获取 API 密钥。我不断收到错误“无法将参数类型'String'分配给参数类型'Uri'。”。这甚至意味着什么？我该如何让它发挥作用？

main.dart

import 'package:flutter/material.dart';
import 'package:font_awesome_flutter/font_awesome_flutter.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';

void main() => runApp(
  MaterialApp(
    title: "Weather App",
    home: Home(),
  )
);

class Home extends StatefulWidget {
  @override
  State<StatefulWidget> createState(){
    return _HomeState();
  }
}

class _HomeState extends State<Home> {

  var temp;
  var description;
  var currently;
  var humidity;
  var windSpeed;

  Future getWeather () async {
    http.Response response = await http.get("http://api.weatherapi.com/v1/current.json?key=e5bd00e528e346ff8a840254213009&q=Chatham Ontario&aqi=no");
    var results = jsonDecode(response.body);
    setState((){
      this.temp = results['current']['temp_c'];
      this.description = results['current'][0]['last_updated'];
      this.currently = results['current'][0]['condition']['text'];
      this.humidity = results['current']['humidity'];
      this.windSpeed = results['current']['wind_kph'];
    });
  }

  @override
  void initState() {
    super.initState();
    this.getWeather();
  }

  @override
  Widget build (BuildContext context) {
    return Scaffold(
      body: Column(
        children: <Widget>[
          Container(
            height: MediaQuery.of(context).size.height / 3,
            width: MediaQuery.of(context).size.width,
            color: Colors.red,
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              crossAxisAlignment: CrossAxisAlignment.center,
              children: <Widget>[
                Padding(
                  padding:EdgeInsets.only(bottom: 10.0),
                  child: Text(
                    "Currently in Chatham-Kent",
                    style: TextStyle(
                      color: Colors.white,
                      fontSize: 14.0,
                      fontWeight: FontWeight.w600
                    ),
                  ),
                ),
                Text(
                  temp != null ? temp.toString() + "\u00B0" : "Loading",
                  style: TextStyle(
                    color: Colors.white,
                    fontSize: 40.0,
                    fontWeight: FontWeight.w600
                  ),
                ),
                Padding(
                  padding:EdgeInsets.only(top: 10.0),
                  child: Text(
                    currently != null ? currently.toString() : "Loading",
                    style: TextStyle(
                        color: Colors.white,
                        fontSize: 14.0,
                        fontWeight: FontWeight.w600
                    ),
                  ),
                ),
              ],
            ),
          ),
          Expanded(
            child: Padding(
              padding: EdgeInsets.all(20.0),
              child: ListView(
                children: <Widget>[
                  ListTile(
                    leading: FaIcon(FontAwesomeIcons.thermometerHalf),
                    title: Text("Temperature"),
                    trailing: Text(temp != null ? temp.toString() + "\u00B0" : "Loading"),
                  ),
                  ListTile(
                    leading: FaIcon(FontAwesomeIcons.cloud),
                    title: Text("Weather"),
                    trailing: Text(description != null ? description.toString() : "Loading"),
                  ),
                  ListTile(
                    leading: FaIcon(FontAwesomeIcons.sun),
                    title: Text("Humidity"),
                    trailing: Text(humidity != null ? humidity.toString() : "Loading"),
                  ),
                  ListTile(
                    leading: FaIcon(FontAwesomeIcons.wind),
                    title: Text("Wind Speed"),
                    trailing: Text(windSpeed != null ? windSpeed.toString() : "Loading"),
                  )
                ],
              )
            )
          )
        ],
      ),
    );
  }
}

pubspec.yaml

version: 1.0.0+1

environment:
  sdk: '>=2.10.0 <3.0.0'

dependencies:
  flutter:
    sdk: flutter
  cupertino_icons: ^1.0.2
  font_awesome_flutter: ^8.0.0
  http: ^0.13.3

dev_dependencies:
  flutter_test:
    sdk: flutter
  flutter_lints: ^1.0.0

flutter:
  uses-material-design: true

Answer 1

嗯，你的错误很明显是The argument type 'String' can't be assigned to the parameter type 'Uri'，所以你必须将url字符串转换为Uri。

像这样：

var uri = Uri.parse("http://api.weatherapi.com/v1/current.json?key=e5bd00e528e346ff8a840254213009&q=Chatham Ontario&aqi=no");
 http.Response response = await http.get(uri);

Answer 2

更改这行代码

http.Response response = await http.get("http://api.weatherapi.com/v1/current.json?key=e5bd00e528e346ff8a840254213009&q=Chatham Ontario&aqi=no");

到

http.Response response = await http.get(Uri.parse("http://api.weatherapi.com/v1/current.json?key=e5bd00e528e346ff8a840254213009&q=Chatham Ontario&aqi=no"));

Answer 3

基于HTTP package docs here.

从 0.13.0-nullsafety.0 版本开始 以前允许传递 String 或 Uri 的所有 API 现在都需要 Uri。 所以这里发生的事情是您需要在调用之前先将您的字符串解析（转换）为uri。

所以你的天气函数会是这样的：

Future getWeather () async {
http.Response response = await http.get(Uri.parse("http://api.weatherapi.com/v1/current.json?key=e5bd00e528e346ff8a840254213009&q=Chatham Ontario&aqi=no"));
var results = jsonDecode(response.body);
setState((){
  this.temp = results['current']['temp_c'];
  this.description = results['current'][0]['last_updated'];
  this.currently = results['current'][0]['condition']['text'];
  this.humidity = results['current']['humidity'];
  this.windSpeed = results['current']['wind_kph'];
});
}