如何解决Android 分页 3 库删除 .cahcedIn(viewModelScope) 将引发异常
我正在我的应用中使用分页 3.0.0-alpha11 库。
有一个具有视图模型的片段。在视图模型中,我实现了这样的分页数据。名为 promoId 的参数有一个可变的实时数据。 promoId 是一个字符串,表示模型的 id。我将它与另一个名为 page 的参数一起使用,以从网络获取一页数据。所以问题是我第一次导航到 te 片段时一切正常,但是在弹出片段并第二次导航到它之后,我收到错误消息并且应用程序崩溃。
我的片段代码。
class ExploreFragment : DaggerFragment() {
private var _binding: FragmentExploreBinding? = null
private val binding get() = _binding!!
@Inject
lateinit var viewModelProviderFactory: ViewModelProviderFactoryImpl
private lateinit var exploreViewModel: ExploreViewModel
lateinit var commentsAdapter: LiveCommentAdapter
override fun onViewCreated(view: View,savedInstanceState: Bundle?) {
initLists()
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
exploreViewModel =
ViewModelProvider(this,viewModelProviderFactory)[ExploreViewModel::class.java]
observeComments()
commentsViewModel.getPromoComments(promoId)
}
}
private fun initLists() {
commentsAdapter = LiveCommentAdapter()
binding.rvComments.adapter = commentsAdapter
binding.rvSearchResults.adapter = searchResultAdapter
}
private fun observeComments() {
exploreViewModel.commentsLiveData.observe(viewLifecycleOwner) { comments ->
commentsAdapter.submitData(viewLifecycleOwner.lifecycle,comments)
}
}
override fun onDestroyView() {
super.onDestroyView()
_binding = null
}
}
这是我的视图模型
另请注意,在 commentRepository.getCommentsByPromo(promoId?:"") 之后我没有使用 cachedIn(viewModelScope) 因为它缓存数据并且不会第二次调用分页数据的 load 方法。
class ExploreViewModel @Inject constructor(
@Inject @JvmField var commentRepository: CommentRepository,) :
ViewModel() {
private val promoIdLiveData: MutableLiveData<String?> = MutableLiveData()
var commentsLiveData: LiveData<PagingData<Comment>> = promoIdLiveData.switchMap { promoId ->
commentRepository.getCommentsByPromo(promoId?:"")
}
fun getComments(promoId: String) {
promoIdLiveData.value = promoId
}
}
这是我的存储库代码。
class CommentRepository @Inject constructor(@Inject @JvmField var retrofit: Retrofit) {
private val api: CommentsApi = retrofit.create(CommentsApi::class.java)
fun getCommentsByPromo(promoId: String):LiveData<PagingData<Comment>> = Pager(
config = PagingConfig(pageSize = 20,enablePlaceholders = false,prefetchDistance = 100),pagingSourceFactory = { PromoCommentPagingSource(promoId,api) }
).liveData
}
我得到的错误是
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.tivasoft.project,PID: 28896
java.lang.IllegalStateException: Attempt to collect twice from pageEventFlow,which is an illegal operation. Did you forget to call Flow<PagingData<*>>.cachedIn(coroutineScope)?
at androidx.paging.PageFetcherSnapshot$pageEventFlow$1.invokeSuspend(PageFetcherSnapshot.kt:88)
at androidx.paging.PageFetcherSnapshot$pageEventFlow$1.invoke(Unknown Source:10)
at androidx.paging.CancelableChannelFlowKt$cancelableChannelFlow$1.invokeSuspend(CancelableChannelFlow.kt:35)
at androidx.paging.CancelableChannelFlowKt$cancelableChannelFlow$1.invoke(Unknown Source:10)
at kotlinx.coroutines.flow.ChannelFlowBuilder.collectTo$suspendImpl(Builders.kt:344)
at kotlinx.coroutines.flow.ChannelFlowBuilder.collectTo(Unknown Source:0)
at kotlinx.coroutines.flow.internal.ChannelFlow$collectToFun$1.invokeSuspend(ChannelFlow.kt:60)
at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106)
at kotlinx.coroutines.EventLoop.processUnconfinedEvent(EventLoop.common.kt:69)
at kotlinx.coroutines.internal.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:349)
at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:30)
at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable$default(Cancellable.kt:27)
at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:109)
at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:158)
at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch(Builders.common.kt:56)
at kotlinx.coroutines.BuildersKt.launch(Unknown Source:1)
at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch$default(Builders.common.kt:49)
at kotlinx.coroutines.BuildersKt.launch$default(Unknown Source:1)
at androidx.paging.AsyncPagingDataDiffer.submitData(AsyncPagingDataDiffer.kt:156)
at androidx.paging.PagingDataAdapter.submitData(PagingDataAdapter.kt:172)
at com.tivasoft.project.ui.explore.ExploreFragment$observeComments$$inlined$observe$1.onChanged(LiveData.kt:52)
at androidx.lifecycle.LiveData.considerNotify(LiveData.java:131)
at androidx.lifecycle.LiveData.dispatchingValue(LiveData.java:144)
at androidx.lifecycle.LiveData$ObserverWrapper.activeStateChanged(LiveData.java:443)
at androidx.lifecycle.LiveData$LifecycleBoundObserver.onStateChanged(LiveData.java:395)
at androidx.lifecycle.LifecycleRegistry$ObserverWithState.dispatchEvent(LifecycleRegistry.java:361)
at androidx.lifecycle.LifecycleRegistry.forwardPass(LifecycleRegistry.java:300)
at androidx.lifecycle.LifecycleRegistry.sync(LifecycleRegistry.java:339)
at androidx.lifecycle.LifecycleRegistry.moveToState(LifecycleRegistry.java:145)
at androidx.lifecycle.LifecycleRegistry.handleLifecycleEvent(LifecycleRegistry.java:131)
at androidx.fragment.app.FragmentViewLifecycleOwner.handleLifecycleEvent(FragmentViewLifecycleOwner.java:51)
at androidx.fragment.app.Fragment.performStart(Fragment.java:2737)
at androidx.fragment.app.FragmentStateManager.start(FragmentStateManager.java:365)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1194)
at androidx.fragment.app.FragmentManager.addAddedFragments(FragmentManager.java:2224)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1997)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1953)
at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1849)
at androidx.fragment.app.FragmentManager$4.run(FragmentManager.java:413)
at android.os.Handler.handleCallback(Handler.java:883)
at android.os.Handler.dispatchMessage(Handler.java:100)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
如果有人能告诉我出了什么问题,我将不胜感激
解决方法
我对您想要发生的事情感到有些困惑,但我的理解是,每当您返回时,您都希望从头开始重新加载。
错误是说您不能在 .submitData
的同一个实例上调用 PagingData
两次。您实际上是在无意中尝试加载缓存数据,并且由于您没有调用 cachedIn
,因此分页会引发异常。
强制 Paging 每次都从头开始加载的一种简单方法是确保每次都构建一个新的 Pager
实例。
所以我会尝试在 observeComments()
中调用 onViewCreated
并将 commentsLiveData
变成一个函数(而不是 var),每次调用时都会返回一个新的 LiveData<PagingData>
。
只需替换 MutableLiveData
private val promoIdLiveData: MutableLiveData<String?> = MutableLiveData()
使用 SingleLiveEvent
private val promoIdLiveData: SingleLiveEvent<String?> = SingleLiveEvent()
SingleLiveEvent
class SingleLiveEvent<T> : MutableLiveData<T>() {
private val pending = AtomicBoolean(false)
@MainThread
override fun observe(owner: LifecycleOwner,observer: Observer<in T>) {
if (hasActiveObservers()) {
Log.w(TAG,"Multiple observers registered but only one will be notified of changes.")
}
// Observe the internal MutableLiveData
super.observe(
owner,Observer { t ->
if (pending.compareAndSet(true,false)) {
observer.onChanged(t)
}
}
)
}
@MainThread
override fun setValue(t: T?) {
pending.set(true)
super.setValue(t)
}
/**
* Used for cases where T is Void,to make calls cleaner.
*/
@MainThread
fun call() {
value = null
}
companion object {
private val TAG = "SingleLiveEvent"
}
}
版权声明:本文内容由互联网用户自发贡献,该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 dio@foxmail.com 举报,一经查实,本站将立刻删除。