通过新的网络呼叫刷新DataSource

Question

单击ui时，我试图刷新我的ViewModel中的LiveData。但是，我不知道如何。我正在尝试重置DataSource.Factory，然后使其无效，但它仍然从第一次加载相同的网络调用。

ViewModel：

class RedditViewModel @Inject constructor(val redditService: LedditService,
                                      val sharedPrefsManager: SharedPrefsManager): ViewModel() {

    private val subredditName = MutableLiveData<String>()
    private var dataSourceFactory = TopicDataSourceFactory(redditService, sharedPrefsManager.lastSubreddit)

    private val config = PagedList.Config.Builder()
            .setEnablePlaceholders(false)
            .setPageSize(30)
            .setInitialLoadSizeHint(60)
            .build()

    var topicList = switchMap(subredditName) {LivePagedListBuilder<String, Children<Topic>>(dataSourceFactory, config).build()}


    fun switchSub(sub: String){
        if(subredditName.value != sub){
            subredditName.value = sub
            sharedPrefsManager.lastSubreddit = sub
            dataSourceFactory = TopicDataSourceFactory(redditService, sharedPrefsManager.lastSubreddit)
            dataSourceFactory.postData.value?.invalidate()
        }
    }

}

TopicDataSourceFactory：

class TopicDataSourceFactory(private val service: LedditService,
                             private val subredditName: String): DataSource.Factory<String, Children<Topic>>() {

    val postData = MutableLiveData<TopicPageKeyedDataSource>()

    override fun create(): DataSource<String, Children<Topic>> {
        val dataSource = TopicPageKeyedDataSource(service, subredditName)
        postData.postValue(dataSource)
        return dataSource
    }
}