1，创建ViewModel类

//MainViewModel.kt
import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.ViewModel
import com.example.myapplication.entity.Banner
import com.example.myapplication.network.BaseResponse
import com.example.myapplication.network.NetworkUtil
import retrofit2.Call
import retrofit2.Callback
import retrofit2.Responseclass MainViewModel : ViewModel() {private val _errorLiveData: MutableLiveData<String> = MutableLiveData()val errorLiveData: LiveData<String> = _errorLiveDataprivate val _bannerLiveData = MutableLiveData<List<Banner>>()val bannerLiveData:LiveData<List<Banner>> = _bannerLiveDatafun getBanners(){NetworkUtil.wanAndroidApi.getBanners().enqueue(object : Callback<BaseResponse<List<Banner>>> {override fun onResponse(call: Call<BaseResponse<List<Banner>>>,response: Response<BaseResponse<List<Banner>>>) {_bannerLiveData.value=response.body()?.data}override fun onFailure(call: Call<BaseResponse<List<Banner>>>,t: Throwable) {_errorLiveData.value = t.message.toString()}})}
}

2,引用ViewModel

//MainActivity.kt
class MainActivity : ComponentActivity() {private lateinit var mViewModel:MainViewModeloverride fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)setContent {Column(Modifier.fillMaxSize(), horizontalAlignment = Alignment.CenterHorizontally) { var textState by rememberSaveable { mutableStateOf("Initial Text")}                mViewModel.bannerLiveData.observe(this@MainActivity){textState = it.toString() }Button(onClick = { mViewModel.getBanners() }) { Text(text = "获取网络信息") } Text(text = textState) }}mViewModel = ViewModelProvider(this)[MainViewModel::class.java]}}