我不能使用Gson将Json文件解析为java对象。

Question

我有一个这样的Json文件：

{
 "airports": [
  {
   "fs": "VGO",
   "iata": "VGO",
   "icao": "LEVX",
   "name": "Vigo Airport",
   "city": "Vigo",
   "cityCode": "VGO",
   "stateCode": "SP",
   "countryCode": "ES",
   "countryName": "Spain and Canary Islands",
   "regionName": "Europe",
   "timeZoneRegionName": "Europe/Madrid",
   "localTime": "2018-01-29T08:59:15.661",
   "utcOffsetHours": 1,
   "latitude": 42.224551,
   "longitude": -8.634025,
   "elevationFeet": 860,
   "classification": 4,
   "active": true,
   "weatherUrl": "https://api.flightstats.com/flex/weather/rest/v1/json/all/VGO?codeType=fs",
   "delayIndexUrl": "https://api.flightstats.com/flex/delayindex/rest/v1/json/airports/VGO?codeType=fs"
  }
 ]
}

我想用来创建一个airport对象。

public class Airport {

    String iata;
    String name;
    String city;
    String countryName;
    String regionName;
    String timeZoneRegionName;
    double utcOffsetHours;

    double latitude;
    double longitude;
    int elevationFeet;

    @Override
    public String toString() {
        return "Airports{" +
                "iata='" + iata + '\'' +
                ", name='" + name + '\'' +
                ", city='" + city + '\'' +
                ", countryName='" + countryName + '\'' +
                ", regionName='" + regionName + '\'' +
                ", timeZoneRegionName='" + timeZoneRegionName + '\'' +
                ", utcOffsetHours=" + utcOffsetHours +
                ", latitude=" + latitude +
                ", longitude=" + longitude +
                ", elevationFeet=" + elevationFeet +
                '}';
    }
}

我是这样读的：

public void imprimirJson(String fileName) {

        String filePath = getCacheDir() + "/" + fileName + ".json";
        Gson gson = new Gson();
        Airport airport = null;

        try {
            airport = gson.fromJson(new FileReader(filePath), Airport.class);
        } catch (FileNotFoundException e) {
        }
        Log.i("MSG", airport.toString());
    }

但如果我执行此代码，日志将打印一个空数组

public void printJson(String fileName) {

        String filePath = getCacheDir() + "/" + fileName + ".json";
        Gson gson = new Gson();
        Airport airport = null;

        try {
            airport = gson.fromJson(new FileReader(filePath), Airport.class);
        } catch (FileNotFoundException e) {
        }
        Log.i("MSG", airport.toString());
    }

我认为问题在于第一个属性有一个我想要的信息数组。但我不知道怎么获取信息。你能给我带路吗？

Answer 1

创建一个类MyAirports.java。

public class MyAirports{
    List<Airport> airports;
    public List<Airport> getAirportList()
    {
        return this.airports;
    }
}

而且确实如此，

 public void printJson(String fileName) {

    String filePath = getCacheDir() + "/" + fileName + ".json";
    Gson gson = new Gson();
    MyAirports airports = null;

    try {
        //airport = gson.fromJson(new FileReader(filePath), Airport.class);
        airports = gson.fromJson(new FileReader(filePath), MyAirports.class);
    } catch (FileNotFoundException e) {
    }
    Log.i("MSG", airports.getAirportList().get(0).toString());
}

Answer 2

json文件中"airports“的值是一个JsonArray。因此，您可以像这样实现：

public void imprimirJson(String fileName) {

        String filePath = getCacheDir() + "/" + fileName + ".json";
        Gson gson = new Gson();
        Airport[] airport = null;

        try {
            airport = gson.fromJson(new FileReader(filePath), Airport[].class);
        } catch (FileNotFoundException e) {
        }
        Log.i("MSG", airport.toString());
    }

稍后，airport就是您要打印的内容。