在响应中获取空值

Question

我正在尝试从 https://www.reddit.com/r/popular/.rss 获取响应并映射到 Android 中的 Kotlin POJO class。但是当我记录该类别的标签值时，结果为空。对于标题，我得到的响应值是流行链接。

这是实体 class 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class：-

@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
}

这里是Api界面：-

interface FeedApi {

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

}

这是 MainActivity:-

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，而 category 标签没有。请参阅下面的差异。

<title>popular links</title>

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

如您所见，category 标签自动关闭。

在响应中获取空值

Getting null value in response

android

kotlin

retrofit