LiveData 不更新

Question

class RequestViewModel(private val repository: RequestRepository) : ViewModel() {

// request currency type
private val currencySearchType = MutableLiveData<String>()

val requests: LiveData<PagedList<Request>> = repository.getRequests(currencySearchType.value!!)

fun updateSearchType(type: String) {
    currencySearchType.postValue(type)
}}

以上是我的viewModel中的代码。

private fun initAdapter() {
        recyclerView.adapter = adapter
        viewModel.requests.observe(viewLifecycleOwner, Observer {
            adapter.submitList(it)
        })
}

这是片段中的代码。所以基本上，我所做的是在 viewModel 中观察 "requests"，在片段中，我还将调用 updateSearchType 来更新 currencySearchType。我希望一旦 currencySearchType 改变，那么 viewmodel.requests 也会改变。但事实证明，这些请求再也不会被调用了。有谁知道哪里出了问题？感谢您的帮助！

Answer 1

更改 currencySearchType 的值不会触发您只是将其用作函数参数的实时数据。你必须为此使用转换。

https://developer.android.com/reference/android/arch/lifecycle/Transformations

class RequestViewModel(private val repository: RequestRepository) : ViewModel() {

// request currency type
lateinit var currencySearchType:String

val requests: LiveData<PagedList<Request>> = Transformations.switchMap(currencySearchType) { repository.getRequests(it) }

fun updateSearchType(type: String) {
    currencySearchType = type
}}

LiveData 不更新

LiveData does not update

android

android-livedata

mutablelivedata