如何使用 Retrofit2 编写 POJO 以从 JSON 中获取对象内的特定数组？

Question

嗯，我需要做一个任务：新闻分页列表。为此，我从 googlesample/architecthurecomponents/PagingWithNetworkSample 中抽取了一个样本并遇到了这个问题。问题是关于 google 样本中解析 JSON 文件的代码。

JSON url: https://www.reddit.com/r/androiddev/hot.json

POJO 文件：

@Entity(tableName = "posts",
    indices = [Index(value = ["subreddit"], unique = false)])
data class RedditPost(
    @PrimaryKey
    @SerializedName("name")
    val name: String,
    @SerializedName("title")
    val title: String,
    @SerializedName("score")
    val score: Int,
    @SerializedName("author")
    val author: String,
    @SerializedName("subreddit") // this seems mutable but fine for a demo
    @ColumnInfo(collate = ColumnInfo.NOCASE)
    val subreddit: String,
    @SerializedName("num_comments")
    val num_comments: Int,
    @SerializedName("created_utc")
    val created: Long,
    val thumbnail: String?,
    val url: String?) {
// to be consistent w/ changing backend order, we need to keep a data like this
var indexInResponse: Int = -1
}

这是一个 api 接口：

interface RedditApi {
@GET("/r/{subreddit}/hot.json")
fun getTop(
        @Path("subreddit") subreddit: String,
        @Query("limit") limit: Int): Call<ListingResponse>

@GET("/r/{subreddit}/hot.json")
fun getTopAfter(
        @Path("subreddit") subreddit: String,
        @Query("after") after: String,
        @Query("limit") limit: Int): Call<ListingResponse>

@GET("/r/{subreddit}/hot.json")
fun getTopBefore(
        @Path("subreddit") subreddit: String,
        @Query("before") before: String,
        @Query("limit") limit: Int): Call<ListingResponse>

class ListingResponse(val data: ListingData)

class ListingData(
        val children: List<RedditChildrenResponse>,
        val after: String?,
        val before: String?
)

data class RedditChildrenResponse(val data: RedditPost)

companion object {
    private const val BASE_URL = "https://www.reddit.com/"
    fun create(): RedditApi = create(HttpUrl.parse(BASE_URL)!!)
    fun create(httpUrl: HttpUrl): RedditApi {
        val logger = HttpLoggingInterceptor(HttpLoggingInterceptor.Logger {
            Log.d("API", it)
        })
        logger.level = HttpLoggingInterceptor.Level.BASIC

        val client = OkHttpClient.Builder()
                .addInterceptor(logger)
                .build()
        return Retrofit.Builder()
                .baseUrl(httpUrl)
                .client(client)
                .addConverterFactory(GsonConverterFactory.create())
                .build()
                .create(RedditApi::class.java)
    }
}
}

问题是：api 请求如何准确地找到我们需要的内容，一个 children: [...]，代表一个帖子列表？因为 children: [...] 驻留在对象内部，并且在代码中我们没有带有 @Serialized("children") 字段的 POJO。仅用于儿童内部物品的 pojo：[...]。我试图实现这种特定于我的 json 的方法，但它 returns 是一个空值。

感谢大家的帮助。

Answer 1

如果 POJO 中的字段名称与 JSON 中的字段名称相同，则不必添加 @SerializedName 注释。这就是为什么 class ListingResponse(val data: ListingData) 可以映射到

{
  "kind": "Listing",
  "data": ...
}

如何使用 Retrofit2 编写 POJO 以从 JSON 中获取对象内的特定数组？

How to write POJOs to get specific array inside an object from JSON using Retrofit2?

json

kotlin

retrofit2

pojo