如果我需要在一些参数改变后重新加载数据，在MVVM中使用实时数据的正确方法是什么?

Question

我有一个项目，它的一部分使用MVVM架构，我使用一个repo从后端获取数据，像这样:

private val spotlights: MutableLiveData<List<SpotlightModel>> = MutableLiveData()
fun getSpotLight(segmentId: String, segmentType: String): MutableLiveData<List<SpotlightModel>>? {
mProvider.getSpotLight(
segmentType = segmentType,
adType = TYPE_SPOT_LIGHT,
segmentId = segmentId,
topics = application.profileManger.topicsIds,
publishers = application.profileManger.publisherIds,
debug = application.debugFlag,deviceId = application.idfa)
.enqueue(object : Callback<List<SpotlightModel>> {
override fun onResponse(call: Call<List<SpotlightModel>>, response: Response<List<SpotlightModel>>) {

if (response.isSuccessful) {
spotlights.postValue(response.body())
}
}
override fun onFailure(call: Call<List<SpotlightModel>>, t: Throwable) {

spotlights.postValue(null)
}
})
return spotlights
}

然后在视图模型中我这样做::

class SpotlightViewModel(val application: NewsApplication) :ViewModel() {
var segmentType: String=""
var segmentId:String=""
val repository=SpotlightRepository(application)
var spotslightsLiveData=repository.getSpotLight(segmentId,segmentType)!!
//if I didn't add this method the data doesn't comeback
fun getSpotLights() {
spotslightsLiveData= repository.getSpotLight(segmentId,segmentType)!!
}}

我是这样观察的

fun getSpotlights(s_id:String, s_type:String){
spotlightViewModel?.segmentId=s_id
spotlightViewModel?.segmentType=s_type

spotlightViewModel?.spotslightsLiveData?.removeObservers(viewLifecycleOwner)
spotlightViewModel?.spotslightsLiveData?.observe(viewLifecycleOwner, Observer

{ spotlightList ->
if (spotlightList.isNullOrEmpty()) {
newNewsAdapter?.spotLights = null
newNewsAdapter?.notifyItemChanged(0)
}
else if (spotlightList.isNotEmpty()) {
newNewsAdapter?.spotLights = spotlightList
newNewsAdapter?.notifyItemChanged(0)
}
})  
spotlightViewModel?.getSpotLights() }

这段代码工作得很好，但是观察者被调用了很多次，我也可以在这里使用一个开关映射吗?提前感谢:)

Answer 1

可以使用switchMap:

val resultLiveData = paramsLiveData.switchMap { params ->
getLiveDataBy(params)
}