Kotlin cannot object before array

Question

I got this error when I am trying to get json array from JSONObject ArrivedResult .

Here is my json :

{
  "ArrivedResult": {
    "arrivals": [
      {
        "ident": "MSR637",
        "aircrafttype": "A321",
        "actualdeparturetime": 1541399820,
        "actualarrivaltime": 1541406652,
        "origin": "HECA"
      }
    ]
  }
}

my code is

private fun handleJson(jsonString: String?) {
    val jsonObj = JSONObject(jsonString)
    val ArrivedResult = jsonObj.getJSONObject("ArrivedResult")
    val jsonArray = JSONArray(ArrivedResult.get("arrivals").toString())

    val list =  ArrayList<FlightShdu>()
    var x = 0
    while (x < jsonArray.length()) {
        val jsonObject = jsonArray.getJSONObject(x)
        list.add(FlightShdu(
            jsonObject.getString("aircrafttype"),
            jsonObject.getString("destination")
        ))
        x++
    }
}

The error I got is Caused by: org.json.JSONException: No value for ArrivedResult

Are you sure that jsonString inside handleJson() function is not null and have exactly same structure as you expect? — ConstOrVar
– ConstOrVar, Commented Nov 5, 2018 at 10:12
Maybe use some external library like kotlinx.serialization? github.com/Kotlin/kotlinx.serialization — Cililing
– Cililing, Commented Nov 5, 2018 at 10:25

asm0dey · Accepted Answer · 2020-01-18 05:47:30Z

I'm not sure what library you're using to deserialize JSON, but if you have fallback to using another ones than it's pretty easy. Foe example with Klaxon:

// To parse the JSON, install Klaxon and do:
//
//   val root = Root.fromJson(jsonString)

import com.beust.klaxon.*

private val klaxon = Klaxon()

data class Root (
    @Json(name = "ArrivedResult")
    val arrivedResult: ArrivedResult
) {
    public fun toJson() = klaxon.toJsonString(this)

    companion object {
        public fun fromJson(json: String) = klaxon.parse<Root>(json)
    }
}

data class ArrivedResult (
    val arrivals: List<Arrival>
)

data class Arrival (
    val ident: String,
    val aircrafttype: String,
    val actualdeparturetime: Long,
    val actualarrivaltime: Long,
    val origin: String
)

Or with kotlinx.serialization

// To parse the JSON, install kotlin's serialization plugin and do:
//
// val json = Json(JsonConfiguration.Stable)
// val root = json.parse(Root.serializer(), jsonString)

import kotlinx.serialization.*
import kotlinx.serialization.json.*
import kotlinx.serialization.internal.*

@Serializable
data class Root (
    @SerialName("ArrivedResult")
    val arrivedResult: ArrivedResult
)

@Serializable
data class ArrivedResult (
    val arrivals: List<Arrival>
)

@Serializable
data class Arrival (
    val ident: String,
    val aircrafttype: String,
    val actualdeparturetime: Long,
    val actualarrivaltime: Long,
    val origin: String
)

Please note that in both cases I have top-leve Root class, which is needed to unwrap top-level {} object from your example

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