Question

Android kotlin协程改造。

我想从getPropeties中获取值以将其插入数据库中。我需要帮助吗？我需要该值是User的实例，而不是单位值。我的viewModel类如下。

    import android.app.Application
    import android.content.Context
    import android.util.Log
    import androidx.lifecycle.LiveData
    import androidx.lifecycle.MutableLiveData
    import androidx.lifecycle.ViewModel
    import com.example.android.marsrealestate.database.AppDatabase
    import com.example.android.marsrealestate.database.User
    import com.example.android.marsrealestate.database.UserDao
    import com.example.android.marsrealestate.network.UsersApi
    import com.example.android.marsrealestate.network.UsersProperty
    import kotlinx.coroutines.*
    import retrofit2.Call
    import retrofit2.Callback
    import retrofit2.Response


    class OverviewViewModel(val database: UserDao,
                            application: Application): ViewModel() {
        private var viewModelJob = Job()
        private val coroutineScope = CoroutineScope(
                viewModelJob + Dispatchers.Main )
        private var user = MutableLiveData<User?>()
        // The internal MutableLiveData String that stores the most recent response
        private val _response = MutableLiveData<String>()

        // The external immutable LiveData for the response String
        val response: LiveData<String>
            get() = _response

        init {
            getUsersProperties()

        }

        private fun getUsersProperties(){
            coroutineScope.launch {
                var getPropertiesDeferred =
                        UsersApi.retrofitService.getProperties()
                try {
                    var listResult = getPropertiesDeferred.await()
                    //database.insertUser(listResult)
                    _response.value =
                            "Success: ${listResult} Mars properties retrieved"

                } catch (e: Exception) {
                    _response.value = "Failure: ${e.message}"
                }
            }
        }

        override fun onCleared() {
            super.onCleared()
            viewModelJob.cancel()
        }
    }

谢谢

Answer 1

您正在使用launch，

启动用于执行异步触发并忘记类型对操作结果不感兴趣的操作。

相反，您可以使用async，

异步用于执行异步计算，如果您期望未来的计算结果

private fun getUsersProperties() =
            coroutineScope.async {
                var getPropertiesDeferred =
                        UsersApi.retrofitService.getProperties()
                try {
                    var listResult = getPropertiesDeferred.await()
                    //database.insertUser(listResult)
                    _response.value =
                            "Success: ${listResult} Mars properties retrieved"

                } catch (e: Exception) {
                    _response.value = "Failure: ${e.message}"
                }
              // =================================================
              // ========= Return whatever result you want =======
              // =================================================
            }

您还可以显示getProperties的类型签名是什么吗？

使用Android获取值而不是Kotlin中try catch块中的单位

1 个答案: