如何使用viewmodel从存储库获取数据

class UserRepository(private val apiService: ApiService) {
    suspend fun getUser(): User {
        return apiService.getUser()
    }
}

class UserViewModel(private val userRepository: UserRepository) : ViewModel() {
    private val _user = MutableLiveData<User>()
    val user: LiveData<User> get() = _user

    fun fetchUser() {
        viewModelScope.launch {
            try {
                val user = userRepository.getUser()
                _user.value = user
            } catch (e: Exception) {
                // Handle error
            }
        }
    }
}

class UserActivity : AppCompatActivity() {
    private lateinit var viewModel: UserViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_user)

        val apiService = Retrofit.Builder()
            .baseUrl("https://api.example.com/")
            .addConverterFactory(GsonConverterFactory.create())
            .build()
            .create(ApiService::class.java)

        val userRepository = UserRepository(apiService)
        viewModel = ViewModelProvider(this, object : ViewModelProvider.Factory {
            override fun <T : ViewModel?> create(modelClass: Class<T>): T {
                return UserViewModel(userRepository) as T
            }
        }).get(UserViewModel::class.java)

        viewModel.user.observe(this, Observer { user ->
            // Update UI with user data
        })

        viewModel.fetchUser()
    }
}