无法在 Android 中使用 Retrofit 解析 JSON

Question

我成功命中 API 并获得 json 结果。我可以通过打印 Retrofit 响应正文在日志中看到成功结果。并且还使用 Stetho 作为网络拦截器。

但是，我无法理解为什么 api 响应在存储库的 onResponse() 方法中仍然是 "null"。我相信，我没有传递正确的模型可能是为了 JSON 被正确解析？谁能帮我找出这里的问题是什么？

以下是json：

{
  "photos": {
    "page": 1,
    "pages": 2864,
    "perpage": 100,
    "total": "286373",
    "photo": [
      {
        "id": "49570734898",
        "owner": "165034061@N07",
        "secret": "f3cb2c2590",
        "server": "65535",
        "farm": 66,
        "title": "Hello",
        "ispublic": 1,
        "isfriend": 0,
        "isfamily": 0
      }
    ],
    "photo": [
      {
        "id": "12344",
        "owner": "23444@N07",
        "secret": "f233edd",
        "server": "65535",
        "farm": 66,
        "title": "Hey",
        "ispublic": 1,
        "isfriend": 0,
        "isfamily": 0
      }
    ]
  },
  "stat": "ok"
}

我的 Pojo Class :

data class Photos(
    @SerializedName("page")
    val page: Int,
    @SerializedName("pages")
    val pages: Int,
    @SerializedName("perpage")
    val perpage: Int,
    @SerializedName("photo")
    val photos: List<Photo>,
    @SerializedName("total")
    val total: String
)

data class Photo(
    @SerializedName("farm")
    val farm: Int,
    @SerializedName("id")
    val id: String,
    @SerializedName("isfamily")
    val isFamily: Int,
    @SerializedName("isfriend")
    val isFriend: Int,
    @SerializedName("ispublic")
    val isPublic: Int,
    @SerializedName("owner")
    val owner: String,
    @SerializedName("secret")
    val secret: String,
    @SerializedName("server")
    val server: String,
    @SerializedName("title")
    val title: String
)

改造客户端：

object ApiClient {

    private val API_BASE_URL = "https://api.flickr.com/"

    private var servicesApiInterface: ServicesApiInterface? = null

    fun build(): ServicesApiInterface? {
        val builder: Retrofit.Builder = Retrofit.Builder()
            .baseUrl(API_BASE_URL)
            .addConverterFactory(GsonConverterFactory.create())

        val httpClient: OkHttpClient.Builder = OkHttpClient.Builder()
        httpClient.addInterceptor(interceptor()).addNetworkInterceptor(StethoInterceptor())

        val retrofit: Retrofit = builder
            .client(httpClient.build()).build()
        servicesApiInterface = retrofit.create(
            ServicesApiInterface::class.java
        )

        return servicesApiInterface as ServicesApiInterface
    }

    private fun interceptor(): HttpLoggingInterceptor {
        val httpLoggingInterceptor = HttpLoggingInterceptor()
        httpLoggingInterceptor.level = HttpLoggingInterceptor.Level.BODY
        return httpLoggingInterceptor
    }

    interface ServicesApiInterface {

        @GET("/services/rest/?method=flickr.photos.search")
        fun getImageResults(
            @Query("api_key") apiKey: String,
            @Query("text") text: String,
            @Query("format") format: String,
            @Query("nojsoncallback") noJsonCallback: Boolean
        ): Call<PhotoResponse>

    }

}

操作回调：

interface OperationCallback<T> {
    fun onSuccess(data:List<T>?)
    fun onError(error:String?)
}

照片数据源：

interface PhotoDataSource {

    fun retrievePhotos(callback: OperationCallback<Photo>, searchText: String)
    fun cancel()
}

照片库：

class PhotoRepository : PhotoDataSource {
 private var call: Call<PhotoResponse>? = null

    private val API_KEY = "eff9XXXXXXXXXXXXX"
    val FORMAT = "json"

    companion object {
        val TAG = PhotoRepository::class.java.simpleName
    }

    override fun retrievePhotos(callback: OperationCallback<Photo>, searchText: String) {
        call = ApiClient.build()
            ?.getImageResults(
                apiKey = API_KEY,
                text = searchText,
                format = FORMAT,
                noJsonCallback = true
            )
        call?.enqueue(object : Callback<PhotoResponse> {
            override fun onFailure(call: Call<PhotoResponse>, t: Throwable) {
                callback.onError(t.message)
            }

            override fun onResponse(
                call: Call<PhotoResponse>,
                response: Response<PhotoResponse>
            ) {

                response?.body()?.let {
                    Log.d(TAG, "got api response total pics are  :${it.data?.size}")
                    if (response.isSuccessful && (it.isSuccess())) {
                        callback.onSuccess(it.data)
                    } else {
                        callback.onError(it.msg)
                    }
                }
            }
        })
    }

    override fun cancel() {
        call?.let {
            it.cancel()
        }
    }
}

照片响应：

data class PhotoResponse(val status: Int?, val msg: String?, val data: List<Photo>?) {
    fun isSuccess(): Boolean = (status == 200)
}

Answer 1

尝试更改您的 PhotoResponse 以匹配您的 json 响应。

data class PhotoResponse(
    @SerializedName("stat")
    val status: String?, 
    @SerializedName("photos")
    val photos: Photos?
) {
    fun isSuccess(): Boolean = status.equals("ok", true)
}

然后在onResponse里面，你可以得到List<Photo>如下：

override fun onResponse(
    call: Call<PhotoResponse>,
    response: Response<PhotoResponse>
) {

    response?.body()?.let {

        //This should be your list of photos
        it.photos.photos
    }
}

Answer 2

问题出在您的数据 class 上。您在这里需要一份额外的数据 class。因此，如果您仔细查看 JSON 的回复，您就会明白哪里出了问题。您的照片数据 class 不应该是第一个 class。相反，它应该在另一个 class 里面，让我们说 PhotoApiResponse。您的第一个 class 将包含照片和统计数据。然后休息可以是一样的。

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