[英]Cannot create an instance of class ViewModel unable to find cause
每当我点击标题时，应用程序崩溃都会显示这个 logcat 我是 Android 的新手，使用匕首刀柄、exoplayer、
这是我接触错误的地方：
歌曲片段
@AndroidEntryPoint
class SongFragments : Fragment(R.layout.fragment_song) {
@Inject
lateinit var glide: RequestManager
private lateinit var mainViewModel: MainViewModel
private val songViewModel: SongViewModel by viewModels()
private var curplayingSong: sound? = null
private var playbackState: PlaybackStateCompat? = null
private var shouldUpdateSeekbar = true
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
mainViewModel = ViewModelProvider(requireActivity()).get(MainViewModel::class.java)
subscribeToObservers()
ivPlayPauseDetail.setOnClickListener {
curplayingSong?.let {
mainViewModel.playOrToggleSound(it, true)
}
}
seekBar.setOnSeekBarChangeListener(object : SeekBar.OnSeekBarChangeListener {
override fun onProgressChanged(seekBar: SeekBar?, progress: Int, fromUser: Boolean) {
if (fromUser) {
setCurPlayerTimeToTextView(progress.toLong())
}
}
override fun onStartTrackingTouch(seekBar: SeekBar?) {
shouldUpdateSeekbar = false
}
override fun onStopTrackingTouch(seekBar: SeekBar?) {
seekBar?.let {
mainViewModel.seekTo(it.progress.toLong())
shouldUpdateSeekbar = true
}
}
})
ivSkipPrevious.setOnClickListener {
mainViewModel.skipToPreviousSound()
}
ivSkip.setOnClickListener{
mainViewModel.skipToNextSound()
}
}
private fun updateTitleAndSongImage(sound: sound) {
val title = "${sound.title} - ${sound.subtitle}"
tvSongName.text = title
glide.load(sound.imageUrl).into(ivSongImage)
}
private fun subscribeToObservers() {
mainViewModel.mediaItems.observe(viewLifecycleOwner){
it?.let { result ->
when(result.status){
Status.SUCCESS -> {
result.data?.let { sounds ->
if (curplayingSong == null && sounds.isNotEmpty()) {
curplayingSong = sounds[0]
updateTitleAndSongImage(sounds[0])
}
}
}
else -> Unit
}
}
}
mainViewModel.curPlayingSound.observe(viewLifecycleOwner) {
if(it == null) return@observe
curplayingSong = it.toSong()
updateTitleAndSongImage(curplayingSong!!)
}
mainViewModel.playbackState.observe(viewLifecycleOwner) {
playbackState = it
ivPlayPauseDetail.setImageResource(
if (playbackState?.isPlaying == true) R.drawable.ic_pause else R.drawable.ic_play
)
seekBar.progress = it?.position?.toInt() ?: 0
}
songViewModel.curPlayerPosition.observe(viewLifecycleOwner) {
if (shouldUpdateSeekbar) {
seekBar.progress = it.toInt()
setCurPlayerTimeToTextView(it)
}
}
songViewModel.curSongDuration.observe(viewLifecycleOwner) {
seekBar.max = it.toInt()
val dateFormat = SimpleDateFormat("mm:ss", Locale.getDefault())
tvSongDuration.text = dateFormat.format(it)
}
}
private fun setCurPlayerTimeToTextView(ms: Long) {
val dateFormat = SimpleDateFormat("mm:ss", Locale.getDefault())
tvCurTime.text = dateFormat.format(ms)
}
}
SongviewModel
class SongViewModel @ViewModelInject constructor(
musicServiceConnection: MusicServiceConnection
) : ViewModel() {
private val playbackState = musicServiceConnection.playBackState
private val _curSongDuration = MutableLiveData<Long>()
val curSongDuration: LiveData<Long> = _curSongDuration
private val _curPlayerPosition = MutableLiveData<Long>()
val curPlayerPosition: LiveData<Long> = _curPlayerPosition
init {
updateCurrentplayerPostion()
}
@SuppressLint("NullSafeMutableLiveData")
private fun updateCurrentplayerPostion() {
viewModelScope.launch {
while(true) {
val pos = playbackState.value?.currentPlaybackPosition
if(curPlayerPosition.value != pos){
_curPlayerPosition.postValue(pos)
_curSongDuration.postValue(MusicService.curSoundDuration)
}
delay(UPDATE_PLAYER_POSITION_INTERVAL)
}
}
}
}
日志猫：
2022-08-12 19:11:39.122 10888-10983/com.fridayhouse.snoozz E/ion: ioctl c0044901 failed with code -1: Invalid argument
2022-08-12 19:11:39.318 10888-10888/com.fridayhouse.snoozz E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.fridayhouse.snoozz, PID: 10888
java.lang.RuntimeException: Cannot create an instance of class com.fridayhouse.snoozz.ui.viewmodels.SongViewModel
at androidx.lifecycle.ViewModelProvider$NewInstanceFactory.create(ViewModelProvider.kt:204)
at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.kt:322)
at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.kt:304)
at androidx.lifecycle.SavedStateViewModelFactory.create(SavedStateViewModelFactory.kt:175)
at androidx.lifecycle.SavedStateViewModelFactory.create(SavedStateViewModelFactory.kt:203)
at dagger.hilt.android.internal.lifecycle.HiltViewModelFactory.create(HiltViewModelFactory.java:111)
at androidx.lifecycle.ViewModelProvider$Factory.create(ViewModelProvider.kt:83)
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.kt:187)
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.kt:153)
at androidx.lifecycle.ViewModelLazy.getValue(ViewModelLazy.kt:53)
at androidx.lifecycle.ViewModelLazy.getValue(ViewModelLazy.kt:35)
at com.fridayhouse.snoozz.ui.fragments.SongFragments.getSongViewModel(SongFragments.kt:33)
at com.fridayhouse.snoozz.ui.fragments.SongFragments.subscribeToObservers(SongFragments.kt:121)
at com.fridayhouse.snoozz.ui.fragments.SongFragments.onViewCreated(SongFragments.kt:45)
at androidx.fragment.app.Fragment.performViewCreated(Fragment.java:3128)
at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:552)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:261)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1890)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1814)
at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1751)
at androidx.fragment.app.FragmentManager$5.run(FragmentManager.java:538)
at android.os.Handler.handleCallback(Handler.java:938)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loopOnce(Looper.java:233)
at android.os.Looper.loop(Looper.java:334)
at android.app.ActivityThread.main(ActivityThread.java:8396)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:582)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1068)
Caused by: java.lang.InstantiationException: java.lang.Class<com.fridayhouse.snoozz.ui.viewmodels.SongViewModel> has no zero argument constructor
at java.lang.Class.newInstance(Native Method)
at androidx.lifecycle.ViewModelProvider$NewInstanceFactory.create(ViewModelProvider.kt:202)
at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.kt:322)
at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.kt:304)
at androidx.lifecycle.SavedStateViewModelFactory.create(SavedStateViewModelFactory.kt:175)
at androidx.lifecycle.SavedStateViewModelFactory.create(SavedStateViewModelFactory.kt:203)
at dagger.hilt.android.internal.lifecycle.HiltViewModelFactory.create(HiltViewModelFactory.java:111)
at androidx.lifecycle.ViewModelProvider$Factory.create(ViewModelProvider.kt:83)
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.kt:187)
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.kt:153)
at androidx.lifecycle.ViewModelLazy.getValue(ViewModelLazy.kt:53)
at androidx.lifecycle.ViewModelLazy.getValue(ViewModelLazy.kt:35)
at com.fridayhouse.snoozz.ui.fragments.SongFragments.getSongViewModel(SongFragments.kt:33)
at com.fridayhouse.snoozz.ui.fragments.SongFragments.subscribeToObservers(SongFragments.kt:121)
at com.fridayhouse.snoozz.ui.fragments.SongFragments.onViewCreated(SongFragments.kt:45)
at androidx.fragment.app.Fragment.performViewCreated(Fragment.java:3128)
at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:552)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:261)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1890)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1814)
at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1751)
at androidx.fragment.app.FragmentManager$5.run(FragmentManager.java:538)
at android.os.Handler.handleCallback(Handler.java:938)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loopOnce(Looper.java:233)
at android.os.Looper.loop(Looper.java:334)
at android.app.ActivityThread.main(ActivityThread.java:8396)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:582)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1068)
由于您使用的是 Hilt，因此您不应该使用by viewModels() 。 您应该在 Provider 中设置MusicServiceConnection ，而不是使用private val songViewModel: SongViewModel by viewModels() ，而是使用@Inject private lateinit var songViewModel: SongViewModel 。
我对 Hilt 不是很熟悉，所以无法提供更多指导。 下面解释by viewModels()出了什么问题，以及如果你不使用依赖注入框架，你将如何解决这个问题。
当您在 Activity 或 Fragment 中创建 ViewModel 时，您可以提供负责创建 ViewModel 实例的工厂。 如果您不提供工厂，则使用默认工厂。
如果您的 ViewModel 构造函数的 arguments 是以下之一，则默认工厂只能创建 ViewModel 的实例：
constructor()空构造函数（无参数）constructor(savedStateHandle: SavedStateHandle)constructor(application: Application)constructor(application: Application, savedStateHandle: SavedStateHandle)我认为这没有很好的记录。 我不得不查看 Jetpack 源代码来学习它。
由于您的 ViewModel 需要MusicServiceConnection参数，因此您不能使用默认工厂。 您需要向by viewModels()提供一个明确的ViewModelProvider.Factory作为参数。
此培训有一个示例，为需要构造函数的特殊参数的 ViewModel 创建ViewModelProvider.Factory class。 在您的情况下，解决方案可能如下所示：
class SongViewModelFactory(private val musicServiceConnection: MusicServiceConnection) : ViewModelProvider.Factory {
override fun <T : ViewModel> create(modelClass: Class<T>): T {
require(modelClass.isAssignableFrom(SongViewModel::class.java)) { "Unknown ViewModel class" }
@Suppress("UNCHECKED_CAST")
return SongViewModel(musicServiceConnection) as T
}
}
我不知道您的 MusicServiceConnection class 来自哪里，但让我们假设您可以使用空构造函数为您的 Activity 简单地实例化一次。 然后你会更换
private val songViewModel: SongViewModel by viewModels()
和
private val songViewModel: SongViewModel by viewModels {
SongViewModelFactory(MusicServiceConnection())
}
请注意，您将 lambda function 传递给viewModels ，而不是直接传递工厂的实例。 这是因为工厂只是懒惰地创建了一次，即使你的 Activity 被重新创建了多次（比如用户来回旋转屏幕）。 此 lambda 中的代码仅在应用导航到此屏幕时调用一次，即使为屏幕旋转或其他配置更改重新创建 Activity 也是如此。
@ViewModelInject 已被弃用。 你可以在这里查看更多信息。
在较新的版本中，您需要使用 @AndroidViewModel 注释视图模型 class 并使用 @Inject 注释构造函数。
@AndroidViewModel
class SongViewModel @Inject constructor(
musicServiceConnection: MusicServiceConnection
) : ViewModel()
希望它能解决这个问题。
无法创建 ViewModel 类的实例（无法启动活动 ComponentInfo）
[英]Cannot create an instance of ViewModel class (Unable to start activity ComponentInfo)
声明:本站的技术帖子网页，遵循CC BY-SA 4.0协议，如果您需要转载，请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.