android - 获取空值作为响应

Question

我正在尝试从 https://www.reddit.com/r/popular/.rss 获得回复并映射到 Android 中的 Kotlin POJO 类。但是当我记录该类别的标签值时，得到空值。对于标题，我得到了作为流行链接的响应值。
这是实体类 FeedX:-

@Root(name = "feed", strict = false)
class FeedX {
    @set: Element(name = "category")
    @get: Element(name = "category")
    var category: Category? = null
    val entry: List<Entry>? = null
    val id: String? = null
    val link: List<LinkX>? = null
    @set: Element(name = "title")
    @get: Element(name = "title")
    var title: String? = null
    val updated: String? = null

}

类别类别:-

@Root(name = "category", strict = false)
class Category {
    @set: Element(required = false, name = "_label")
    @get: Element(required = false, name = "_label")
    var _label: String? = null
    val _term: String? = null
}

这是 Api 接口(interface):-

interface FeedApi {

    @GET("{type}/.rss")
    fun getPopularFeeds(
        @Path("type") type: String?
    ): Call<FeedX>?

}

这是主要 Activity :-

class MainActivity : AppCompatActivity() {
    private val BASE_URL = "https://www.reddit.com/r/"
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)


        val retrofit = Retrofit.Builder()
            .baseUrl(BASE_URL)
            .addConverterFactory(SimpleXmlConverterFactory.create())
            .build()

        val service = retrofit.create(FeedApi::class.java)

        service.getPopularFeeds("popular")?.enqueue(object : Callback<FeedX> {
            override fun onFailure(call: Call<FeedX>, t: Throwable) {
                Log.d("Response Failed", "${t.localizedMessage}")
            }

            override fun onResponse(call: Call<FeedX>, response: Response<FeedX>) {
                if (response.isSuccessful) {
                    Log.d("Response Success", "${response.body()!!.title}") // for this I am getting value
                    Log.d("Response Success", "${response.body()!!.category?._label}")  // always getting null value
                } else {
                    Log.d("Response Failed jg", "${response.errorBody()}")
                }
            }
        })
    }
}

Answer 1

这是因为 title包含一个值，其中 category标签没有。请参阅下面的区别。

<title>popular links</title>

<category term="AskReddit" label="r/AskReddit"/>

如您所见 category标签是自动关闭的。