Question

我正在解析来自OpenWeathermap.org的json数据，如下所示：

{
   "cod":"200",
"message":0.0016,
"city":{
  "id":1164408,
  "name":"Sukkur",
  "coord":{
     "lon":68.857384,
     "lat":27.70516
  },
  "country":"PK",
  "population":0,
  "sys":{
     "population":0
  }  },  

"cnt":2,
"list":[
  {
     "dt":1394175600,
     "temp":{
        "day":26.31,
        "min":20,
        "max":30.17,
        "night":22.71,
        "eve":30.17,
        "morn":20
     },
     "pressure":1024.11,
     "humidity":59,
     "weather":[
        {
           "id":801,
           "main":"Clouds",
           "description":"few clouds",
           "icon":"02d"
        }
     ],
     "speed":0.91,
     "deg":121,
     "clouds":12
  },
  {
     "dt":1394262000,
     "temp":{
        "day":25.58,
        "min":18.94,
        "max":28.22,
        "night":21.08,
        "eve":28.22,
        "morn":18.94
     },
     "pressure":1026.39,
     "humidity":58,
     "weather":[
        {
           "id":800,
           "main":"Clear",
           "description":"sky is clear",
           "icon":"01d"
        }
     ],
     "speed":5.75,
     "deg":74,
     "clouds":0
  }
]}

查看此SO Question后，我将Model.java课程作为上述json数据的

public class Model{

protected String cityId = null;
protected String cityName = null;
protected String countryName = null;
protected String longitude = null;
protected String latitude = null;
protected String polution = null;
protected List<ForecatList> forcastList = null;
// getters setters
public class ForecatList {
    protected String dayTimeTemp = null;
    protected String maxTemp = null;
    protected String minTemp = null;
    protected String nightTimeTemp = null;
    protected String eveTimeTemp = null;
    protected String mornTimeTemp = null;
    protected String pressure = null;
    protected String humidity = null;
    protected String windSpeed = null;
    protected String WindDegree = null;
    protected String clouds = null;
    protected List<Weather> weathers = null;
    // getters setters
    public class Weather {
        protected String weatherId = null;
        protected String weatherCondition = null;
        protected String weatherDescription = null;
        protected String weatherIcon = null;
        // getters setters
    }
}}

解析信托是：

public Model getForecastByCityName(Context context, String city, int ofDays){
    Model model = null;     
    try {           
        Gson gson = new Gson();
        Reader reader = new InputStreamReader(forecastByCityName(context, city, ofDays));           
        model = gson.fromJson(reader, Model.class);         
        return model;
    } catch (ClientProtocolException e) {
        e.printStackTrace();
        return null;
    } catch (IOException e) {
        e.printStackTrace();
        return null;
    }   
}

和forecastByCityName()是：

private InputStream forecastByCityName(Context context, String city, int ofDays) throws ClientProtocolException, IOException{
    HttpClient httpClient = null;
    StringBuilder url = new StringBuilder(URL_FORCAST);
    url.append(city);
    url.append(String.valueOf(ofDays));
    url.append(UNIT);
    HttpGet httpRequest = new HttpGet(url.toString());
    httpClient = new DefaultHttpClient();
    HttpResponse httpResponse = httpClient.execute(httpRequest);
    int statusCode = httpResponse.getStatusLine().getStatusCode();
    if (statusCode == 200) {
        HttpEntity httpEntity = httpResponse.getEntity();
        return httpEntity.getContent();
    }else {
        return null;            
    }       
}

我的请求是成功的，但是当我尝试从Model对象获取值时：

textView.setText(model.getCityName() + model.getCountryName());

打印null null null，为什么无法获取值？任何想法..

Answer 1

Model类中的所有字段名称必须等于json keys：for“country” - protected String country;
“city”json key有自己的内部数据，因此您需要创建具有适当字段名称的City类并定义“受保护的城市城市”; Model类中的字段。

这里所有你需要的（100％适用于你的json示例）：

public class Model implements Serializable {

private String cod;
private Double message;
private City city;
private Integer cnt;
private List<ListItem> list = new ArrayList<ListItem>();

public String getCod() {
    return cod;
}

public void setCod(String cod) {
    this.cod = cod;
}

public Double getMessage() {
    return message;
}

public void setMessage(Double message) {
    this.message = message;
}

public City getCity() {
    return city;
}

public void setCity(City city) {
    this.city = city;
}

public Integer getCnt() {
    return cnt;
}

public void setCnt(Integer cnt) {
    this.cnt = cnt;
}

public List<ListItem> getList() {
    return list;
}

public void setList(List<ListItem> list) {
    this.list = list;
}

private class City implements Serializable { 
    private Integer id;
    private String name;
    @SerializedName("coord")
    private Coordinates coordinates;
    private String country;
    private Integer population;
    private Sys sys;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Coordinates getCoordinates() {
        return coordinates;
    }

    public void setCoordinates(Coordinates coordinates) {
        this.coordinates = coordinates;
    }

    public String getCountry() {
        return country;
    }

    public void setCountry(String country) {
        this.country = country;
    }

    public Integer getPopulation() {
        return population;
    }

    public void setPopulation(Integer population) {
        this.population = population;
    }

    public Sys getSys() {
        return sys;
    }

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

    private class Coordinates implements Serializable {
        @SerializedName("lon")
        private Double longitude;
        @SerializedName("lat")
        private Double latitude;

        public Double getLongitude() {
            return longitude;
        }

        public void setLongitude(Double longitude) {
            this.longitude = longitude;
        }

        public Double getLatitude() {
            return latitude;
        }

        public void setLatitude(Double latitude) {
            this.latitude = latitude;
        }
    }

    private class Sys implements Serializable {
        private Integer population;

        public Integer getPopulation() {
            return population;
        }

        public void setPopulation(Integer population) {
            this.population = population;
        }
    }
}

private class ListItem implements Serializable {
    @SerializedName("dt")
    private Long dateTime;
    @SerializedName("temp")
    private Temperature temperature;
    private Double pressure;
    private Integer humidity;
    private List<Weather> weather = new ArrayList<Weather>();
    private Double speed;
    @SerializedName("deg")
    private Integer degree;
    private Integer clouds;

    public Long getDateTime() {
        return dateTime;
    }

    public void setDateTime(Long dateTime) {
        this.dateTime = dateTime;
    }

    public Temperature getTemperature() {
        return temperature;
    }

    public void setTemperature(Temperature temperature) {
        this.temperature = temperature;
    }

    public Double getPressure() {
        return pressure;
    }

    public void setPressure(Double pressure) {
        this.pressure = pressure;
    }

    public Integer getHumidity() {
        return humidity;
    }

    public void setHumidity(Integer humidity) {
        this.humidity = humidity;
    }

    public List<Weather> getWeather() {
        return weather;
    }

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

    public Double getSpeed() {
        return speed;
    }

    public void setSpeed(Double speed) {
        this.speed = speed;
    }

    public Integer getDegree() {
        return degree;
    }

    public void setDegree(Integer degree) {
        this.degree = degree;
    }

    public Integer getClouds() {
        return clouds;
    }

    public void setClouds(Integer clouds) {
        this.clouds = clouds;
    }

    private class Temperature implements Serializable {
        private Double day;
        private Double min;
        private Double max;
        private Double night;
        @SerializedName("eve")
        private Double evening;
        @SerializedName("morn")
        private Double morning;

        public Double getDay() {
            return day;
        }

        public void setDay(Double day) {
            this.day = day;
        }

        public Double getMin() {
            return min;
        }

        public void setMin(Double min) {
            this.min = min;
        }

        public Double getMax() {
            return max;
        }

        public void setMax(Double max) {
            this.max = max;
        }

        public Double getNight() {
            return night;
        }

        public void setNight(Double night) {
            this.night = night;
        }

        public Double getEvening() {
            return evening;
        }

        public void setEvening(Double evening) {
            this.evening = evening;
        }

        public Double getMorning() {
            return morning;
        }

        public void setMorning(Double morning) {
            this.morning = morning;
        }
    }

    private class Weather implements Serializable {
        private Integer id;
        private String main;
        private String description;
        private String icon;

        public Integer getId() {
            return id;
        }

        public void setId(Integer id) {
            this.id = id;
        }

        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;
        }

        public String getIcon() {
            return icon;
        }

        public void setIcon(String icon) {
            this.icon = icon;
        }
    }
}

}

Answer 2

我建议您使用某种工具自动创建模型。我个人一直使用http://www.jsonschema2pojo.org/。

Answer 3

您的POJO不适合JSON输出。您需要为Gson创建城市对象以捕获城市数据。要获取城市和国家/地区名称，您需要执行以下操作;

public class Model {
    private String cod;
    private City city;

    // To catch the forecasts list
    private List<ForecastList> list;

    // Alternatively if you want the variable to be called forecastList
    // you can do the following
    @SerializedName("list")
    private List<ForecastList> forecastList;

    public class City {
        private String name;
        private String country;

        public String getName() {
            return name;
        }

        public String getCountry() {
            return country;
        }
    }

    public City getCity() {
        return city;
    }

    // Omitted for brevity
}

然后，您可以通过执行以下操作获取城市和国家/地区名称;

Gson gson = new Gson();
Reader reader = new InputStreamReader(forecastByCityName(context, city, ofDays));           
Model model = gson.fromJson(reader, Model.class);
String cityName = model.getCity().getName();
String cityCountry = model.getCity().getCountry();

或者，如果您希望在方便的时候在Model上制作一些封装方法。

json解析通过gson返回null

3 个答案: