Question

尝试在Kotlin中解析JSON数组，使其适用于WeatherObject对象的单个JSON对象（下面的代码片段）

{
"coord": {
    "lon": -2.93,
    "lat": 43.26
},

"weather": [{
    "id": 802,
    "main": "Clouds",
    "description": "scattered clouds",
    "icon": "03d"
}],

"main": {
    "temp": 283.681,
    "temp_min": 283.681,
    "temp_max": 283.681,
    "pressure": 991.72,
    "sea_level": 1034.92,
    "grnd_leve": 991.72,
    "humidity": 98
},
"wind": {
    "speed": 1.07,
    "deg": 144.001
},

"dt": 1429773245,
"id": 3128026,
"name": "Bilbao",
"cod": 200

}

但如果JSON是一个具有相同JSON对象的数组，则不确定如何做同样的事情，即

从json数组[{}，{} ...]到ArrayList＆lt; WeatherObject＆gt;

类似的东西：

fun getWeatherObjectArrayFromJson(jsonStr: String): ArrayList&lt;WeatherObject &gt

有gsonBuilder.registerTypeAdapter（ArrayList＆lt; WeatherObject＆amp; gt :: class.java，WeatherDeserializer（））的问题

class WeatherObject {

    var main: String = ""
    var description: String = ""
    var temp: Float = 0.0f
    var tempMax: Float = 0.0f
    var tempMin: Float = 0.0f
    var humidity: Int = 0
    var wind: WindObject? = null

}

class WeatherDeserializer : JsonDeserializer<WeatherObject> {

    override fun deserialize(json: JsonElement?, typeOfT: Type?, context: JsonDeserializationContext?): WeatherObject? {
        val jsonObj = json as JsonObject

        val wheather = WeatherObject()
        val wind = WindObject()

        val jsonWeatherArray = jsonObj.getAsJsonArray("weather").get(0)
        val jsonMainObj = jsonObj.getAsJsonObject("main")
        val jsonWindObj = jsonObj.getAsJsonObject("wind")

        wheather.main = jsonWeatherArray.asJsonObject.get("main").asString
        wheather.description = jsonWeatherArray.asJsonObject.get("description").asString
        wheather.temp = jsonMainObj.get("temp").asFloat
        wheather.tempMax = jsonMainObj.get("temp_max").asFloat
        wheather.tempMin = jsonMainObj.get("temp_min").asFloat
        wheather.humidity = jsonMainObj.get("humidity").asInt
        wind.speed = jsonWindObj.get("speed").asFloat
        wind.deg = jsonWindObj.get("deg").asFloat
        wheather.wind = wind

        return wheather

    }
}

fun getWeatherObjectFromJson(jsonStr: String): WeatherObject {

        var stringReader: StringReader = StringReader(jsonStr)
        var jsonReader: JsonReader = JsonReader(stringReader)

        val gsonBuilder = GsonBuilder().serializeNulls()
        gsonBuilder.registerTypeAdapter(WeatherObject::class.java, WeatherDeserializer())
        val gson = gsonBuilder.create()

        val weather: WeatherObject = gson.fromJson(jsonReader, WeatherObject::class.java)

        return weather
    }

更新

尝试了chandil03的解决方案，它正在工作！把测试json数组和函数放在这里：

尝试

fun getWeatherObjectFromJsonArray(jsonArrayStr: String): List<WeatherObject> {

        var stringReader: StringReader = StringReader(jsonStr)
        //var jsonReader: JsonReader = JsonReader(stringReader)

        val gsonBuilder = GsonBuilder().serializeNulls()
        gsonBuilder.registerTypeAdapter(WeatherObject::class.java, WeatherDeserializer())
        val gson = gsonBuilder.create()

        val weatherList: List<WeatherObject> = gson.fromJson(stringReader , Array<WeatherObject>::class.java).toList()
        //val weatherList: List<WeatherObject> = gson.fromJson(jsonReader, Array<WeatherObject>::class.java).toList

        return weatherList
    }

在

得到例外

val weatherList: List<WeatherObject> = gson.fromJson(stringReader , Array<WeatherObject>::class.java).toList()

com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 1 column 2 path $

json数组数据如下：

[
{
  "coord": {
    "lon": -2.93,
    "lat": 43.26
  },

  "weather": [{
    "id": 802,
    "main": "Clouds",
    "description": "scattered clouds",
    "icon": "03d"
  }],

  "main": {
    "temp": 283.681,
    "temp_min": 283.681,
    "temp_max": 283.681,
    "pressure": 991.72,
    "sea_level": 1034.92,
    "grnd_leve": 991.72,
    "humidity": 98
  },
  "wind": {
    "speed": 1.07,
    "deg": 144.001
  },
  "clouds": {
    "all": 36
  },
  "dt": 1429773245,
  "id": 3128026,
  "name": "Bilbao",
  "cod": 200
}, 

{
  "coord": {
    "lon": -2.93,
    "lat": 43.26
  },

  "weather": [{
    "id": 802,
    "main": "Clouds",
    "description": "scattered clouds",
    "icon": "03d"
  }],

  "main": {
    "temp": 283.681,
    "temp_min": 283.681,
    "temp_max": 283.681,
    "pressure": 991.72,
    "sea_level": 1034.92,
    "grnd_leve": 991.72,
    "humidity": 98
  },
  "wind": {
    "speed": 1.07,
    "deg": 144.001
  },
  "clouds": {
    "all": 36
  },
  "dt": 1429773245,
  "id": 3128026,
  "name": "Bilbao",
  "cod": 200
}
]

Answer 1

您需要更改fromJson()函数调用中的参数，如下所示：

val weatherList: List<WeatherObject> = gson.fromJson(stringReader , Array<WeatherObject>::class.java).toList()

您需要为类类型传递Array<WeatherObject>::class.java，然后将结果转换为List。无需更改registerTypeAdapter()函数调用。

检查以下代码：

fun getWeatherObjectFromJson(jsonStr: String): List<WeatherObject> {

        var stringReader: StringReader = StringReader(jsonStr)
        var jsonReader: JsonReader = JsonReader(stringReader)

        val gsonBuilder = GsonBuilder().serializeNulls()
        gsonBuilder.registerTypeAdapter(WeatherObject::class.java, WeatherDeserializer())
        val gson = gsonBuilder.create()

       val weatherList: List<WeatherObject> = gson.fromJson(stringReader , Array<WeatherObject>::class.java).toList()

        return weatherList
    }

Answer 2

另一种扩展功能：

inline fun <reified T> Gson.fromJson(json: String) = fromJson<T>(json, object : TypeToken<T>() {}.type)

用法：

val str ="[....]"
val list:List<WeatherObject> = Gson().fromJson<List<WeatherObject>>(str)

在Kotlin中使用Gson来解析JSON数组

2 个答案: