为我的 ViewModel class 和 Retrofit class 创建一个 LiveData class

Question

我正在努力为我的 ViewModel class 和我的 Retrofit class 创建一个 LiveData class API 来电。

ViewModel class:

class ApiViewModel : ViewModel() {

    private lateinit var status: String

    @NonNull
    fun getApiResults(param1: String, param2: String, param3: String) {
        viewModelScope.launch {
            try {
                val listResult = ApiCalls.retrofitService.ApiCallsService(param1, param2, param3)
            } catch (e: Exception) {
                status = "Failure: ${e.message}"
            }
        }
    }
}

Retrofit class:

private const val BASE_URL = "https://sampleapiurl.com"

private val moshi = Moshi.Builder().addLast(KotlinJsonAdapterFactory()).build()

private val client = OkHttpClient.Builder()
    .connectTimeout(60, TimeUnit.SECONDS)
    .writeTimeout(60, TimeUnit.SECONDS)
    .readTimeout(60, TimeUnit.SECONDS)
    .build()

private val retrofit = Retrofit.Builder()
    .addConverterFactory(MoshiConverterFactory.create(moshi))
    .baseUrl(BASE_URL)
    .client(client)
    .build()

interface ApiCallsService {
    @GET(".")
    suspend fun apiCalls(
        @Query("param1") param1: String,
        @Query("param2") param2: String,
        @Query("param3") param3: String
    ): Call<CustomDataClass>
}

object ApiCalls {
    val retrofitService: ApiCallsService by lazy { retrofit.create(ApiCallsService::class.java) }
}

现在，在 ViewModel class 的 try catch 语句中，我想将 listResult 的结果传递给 LiveData class.这样在我的 onViewCreated 片段中，我可以做这样的事情来检索数据：

val apiViewModel = ViewModelProvider(this).get(ApiViewModel::class.java)
apiViewModel.getApiResults("val1", "val2", "val3").observe(...

我的 LiveData class 应该如何实现？

Answer 1

您可能需要创建 LiveData 来观察您想要的任何值。在您的情况下，您似乎需要观察 status 和 listResult 的值。因此，我建议您在 ApiViewModel 中创建 LiveData，即

val statusLiveData = MutableLiveData<String>()
val listResultLiveData = MutableLiveData<YourListType>()

和post在你的getApiResults()中的值（修改你的getApiResults()）

@NonNull
fun getApiResults(param1: String, param2: String, param3: String) {
     viewModelScope.launch {
         try {
           listResultLiveData.postValue(ApiCalls.retrofitService.ApiCallsService(param1, param2, param3))
         } catch (e: Exception) {
            statusLiveData.postValue("Failure: ${e.message}")
         }
     }
}

并将其添加到 Fragment

中的 onViewCreated()

apiViewModel.statusLiveData.observe(viewLifecycleOwner, Observer { 
   // TODO: What to do with the status            
})
apiViewModel.listResultLiveData.observe(viewLifecycleOwner, Observer { 
   // TODO: What to do on get list result            
})

为我的 ViewModel class 和 Retrofit class 创建一个 LiveData class

Creating a LiveData class for my ViewModel class and Retrofit class

android

kotlin

retrofit2

android-livedata

android-viewmodel