如何使用带有 Kotlin 的 Gson 库访问 JSON 有效负载中的嵌套值

Posted 2023-04-19

【中文标题】如何使用带有 Kotlin 的 Gson 库访问 JSON 有效负载中的嵌套值

【英文标题】：How can I access the nested value in a JSON payload using Gson library with Kotlin

【发布时间】：2021-10-07 04:56:24

【问题描述】：

下面需要解析JSONpayload：

  "status": "success",
  "data": 
    "stats": 
      "total": 11812,
      "offset": 0,
      "limit": 50,
      "order": "desc",
      "base": "USD",
      "totalMarkets": 77573,
      "totalExchanges": 372,
      "totalMarketCap": 1692792022714.2244,
      "total24hVolume": 78345365115.11235
    ,
    "base": 
      "symbol": "USD",
      "sign": "$"
    ,
    "coins": [
      
        "id": 1,
        "uuid": "Qwsogvtv82FCd",
        "slug": "bitcoin-btc",
        "symbol": "BTC",
        "name": "Bitcoin",
   ...

我对“硬币”价值有疑问：

 fun fetchJson() 
    val url = "https://api.coinranking.com/v1/public/coins"
    val request = Request.Builder().url(url).build()

    val client = OkHttpClient()
    client.newCall(request).enqueue(object: okhttp3.Callback 
        override fun onFailure(call: okhttp3.Call, e: IOException) 
            println("Failed")
        

        override fun onResponse(call: okhttp3.Call, response: okhttp3.Response) 
            val body = response?.body?.string()
            println(body)

            val gson = GsonBuilder().create()
            val coins = gson.fromJson(body, coinrank::class.java)
            println("THESE ARE THE COINS : " +coins)
        
    )

数据模型：

class coinrank(val status: String?, val data: Array<dataR>?)

class dataR (val coins: List<justCoin>?)

class justCoin (
    val id: Int?,
    val name: String?,
    val description: String?,
    val slug: String?,
    val symbol: String?,
    val iconUrl: String?
        )

有一个错误：

引起：java.lang.IllegalStateException：预期 BEGIN_ARRAY 但 在第 1 行第 29 列路径 $.data 处为 BEGIN_OBJECT

在线：val coins = gson.fromJson(body, coinrank::class.java)

我尝试将 val data: Array<dataR>? 更改为 val data: JSONObject" 但我仍然找不到访问这些值的方法，有人可以帮助我吗？

【参考方案1】：

您的数据模型不适合 JSON 有效负载。试试下面：

data class CoinsResponse(
    val status: String,
    val data: CoinsData
)

data class CoinsData(
    val coins: List<Coin>
)

data class Coin(
    val id: Int,
    val symbol: String,
    val name: String
)

示例用法：

val gson = GsonBuilder().create()
val response = gson.fromJson(body, CoinsResponse::class.java)
response.data.coins.forEach(System.out::println)

上面的代码应该打印出来：

Coin(id=1, symbol=BTC, name=Bitcoin)
Coin(id=2, symbol=ETH, name=Ethereum)
Coin(id=8, symbol=USDT, name=Tether USD)
Coin(id=14, symbol=BNB, name=Binance Coin)
Coin(id=9, symbol=ADA, name=Cardano)
Coin(id=3, symbol=XRP, name=XRP)
...