如何使用 Retrofit 从 OpenWeatherMap API 获取“天气”对象数据

Question

我是开发新手，我正在尝试为一项任务开发一个 Android 天气应用程序，我在 youtube 上遵循了这个 tutorial 来创建它，一切正常，但我无法从“天气”中获取数据以下 API 上的对象。
OpenWeatherMap API

{
  "coord": {
    "lon": -122.08,
    "lat": 37.39
  },
  "weather": [
    {
      "id": 800,
      "main": "Clear",
      "description": "clear sky",
      "icon": "01d"
    }
  ],
  "base": "stations",
  "main": {
    "temp": 282.55,
    "feels_like": 281.86,
    "temp_min": 280.37,
    "temp_max": 284.26,
    "pressure": 1023,
    "humidity": 100
  },
  "visibility": 16093,
  "wind": {
    "speed": 1.5,
    "deg": 350
  },
  "clouds": {
    "all": 1
  },
  "dt": 1560350645,
  "sys": {
    "type": 1,
    "id": 5122,
    "message": 0.0139,
    "country": "US",
    "sunrise": 1560343627,
    "sunset": 1560396563
  },
  "timezone": -25200,
  "id": 420006353,
  "name": "Mountain View",
  "cod": 200
  }

ApiClient.java

    package com.dhanurjan.weather.Retrofit;

import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class ApiClient {


    private static Retrofit retrofit = null;

   public static  Retrofit getClient(){ //creating object

        if (retrofit == null){

            retrofit = new Retrofit.Builder() //Retrofit.Builder class uses the Builder API to allow defining the URL end point for the HTTP operations and finally build a new Retrofit instance.
                    //http://api.openweathermap.org/data/2.5/weather?q=London&APPID=76a35a17f3e1bce771a09f3555b614a8
                    .baseUrl("https://api.openweathermap.org/data/2.5/")
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();

        }


        return retrofit;

    }
}

ApiInterface.java

    package com.dhanurjan.weather.Retrofit;

import retrofit2.Call;
import retrofit2.http.GET;
import retrofit2.http.Query;

public interface ApiInterface {


    @GET("weather?APPID=76a35a17f3e1bce771a09f3555b614a8&units=metric")
    Call<Example> getWeatherData(@Query("q") String name);


}

Example.java

    package com.dhanurjan.weather.Retrofit;

import com.google.gson.annotations.SerializedName;

public class Example {

    @SerializedName("sys")
    private Sys sys;

    @SerializedName("coord")
    private Coord coord;

    @SerializedName("main")
    private Main main;

    @SerializedName("weather")
    private Weather weather;

    public Sys getSys() { return sys; }

    public void setSys(Sys sys) {
        this.sys = sys;
    }

    public Coord getCoord() {
        return coord;
    }

    public void setCoord(Coord coord) {
        this.coord = coord;
    }

    public Main getMain() {
        return main;
    }

    public void setMain(Main main) {
        this.main = main;
    }

    public Weather getWeather() { return weather; }

    public void setWeather(Weather weather) { this.weather = weather; }
}

Weather.java

    package com.dhanurjan.weather.Retrofit;

import com.google.gson.annotations.SerializedName;

public class Weather {

        @SerializedName("main")
        String main;

        @SerializedName("description")
        String description;


        public String getMain() { return main; }

        public void setMain(String main) { this.main = main; }

        public String getDescription() { return description; }

        public void setDescription(String description) { this.description = description; }
}

MainActivity.java

    package com.dhanurjan.weather;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import com.dhanurjan.weather.Retrofit.ApiClient;
import com.dhanurjan.weather.Retrofit.ApiInterface;
import com.dhanurjan.weather.Retrofit.Example;

import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;

public class MainActivity extends AppCompatActivity {

    Button searchBtn;
    TextView tempText , feelText , humidityText, lon, lat, country, sunrise, sunset, descText;
    EditText cityName;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        searchBtn = findViewById(R.id.searchBtn);
        tempText = findViewById(R.id.tempText);
        feelText = findViewById(R.id.feelText);
        humidityText = findViewById(R.id.humidityText);
        country = findViewById(R.id.country);
        sunrise = findViewById(R.id.sunrise);
        sunset = findViewById(R.id.sunset);
        lon = findViewById(R.id.lonText);
        lat = findViewById(R.id.latText);
        cityName = findViewById(R.id.cityName);
        descText = findViewById(R.id.descText);


        searchBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {


                getWeatherData(cityName.getText().toString().trim());

            }
        });
    }

    private void getWeatherData(String name){

        ApiInterface apiInterface = ApiClient.getClient().create(ApiInterface.class);

        Call<Example> call = apiInterface.getWeatherData(name);

        call.enqueue(new Callback<Example>() {
            @Override
            public void onResponse(Call<Example> call, Response<Example> response) {

                tempText.setText("Temperature :"+" "+response.body().getMain().getTemp()+" ℃");
                feelText.setText("Feels Like :"+" "+response.body().getMain().getFeels_like()+" ℃");
                lon.setText("Longitude :"+" "+response.body().getCoord().getLon()+" °E");
                lat.setText("Latitude :"+" "+response.body().getCoord().getLat()+" °N");
                humidityText.setText("Humidity :"+" "+response.body().getMain().getHumidity()+" %");
                country.setText("country :"+" "+response.body().getSys().getCountry());
                sunrise.setText("sunrise :"+" "+response.body().getSys().getSunrise()+" AM");
                sunset.setText("sunset :"+" "+response.body().getSys().getSunset()+" PM");
                descText.setText("descText :"+" "+response.body().getWeather().getDescription());


            }

            @Override
            public void onFailure(Call<Example> call, Throwable t) {

            }
        });

    }
}



                                    

Answer 1

代码的主要问题是：

@SerializedName("weather")
private Weather weather;

对应的JSON是：

"weather": [
    {
        "id": 800,
        "main": "Clear",
        "description": "clear sky",
        "icon": "01d"
    }]

虽然它只有 1 项，但由于“[”和“]”，它实际上是一个 Weather 对象的 JSON 数组

Retrofit注解需要改成：

@SerializedName("weather")
private List<Weather> weatherList;

而getter和setter需要改成：

public List<Weather> getWeatherList() { return weatherList; }

public void setWeatherList(List<Weather> weatherList) { this.weatherList = weatherList; }

显示天气信息的代码需要更新为：

response.body().getWeatherList().get(0).getDescription();

这将获得第一个 Weather 对象，如果没有则崩溃。

但是我的项目中正在运行您的代码，所以如果您遇到任何其他问题，请告诉我。

最后，对于任何正在寻找更简单的 API 来学习 Retrofit 的人： https://dog.ceo/api/breeds/image/random

这是一个只返回 2 个字段的 GET。