I'm struggling with creating a LiveData class for my ViewModel class and my Retrofit class that makes API calls.

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) }
}

Now, inside the try catch statement in my ViewModel class, I want to pass the result of listResult into a LiveData class. That way in my onViewCreated in my fragments, I can do something like this to retrieve the data:

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

How should my LiveData class look so I can achieve this?

CodePudding user response：

You may need to create LiveData to observe any values you desired. In your case, seems you need to observe the value of status and listResult. Therefore, I suggest you create LiveData in ApiViewModel, i.e.

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

and post value to it in your getApiResults() (modify your 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}")
         }
     }
}

and add this to onViewCreated() in the Fragment

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            
})