我剛剛在我的應用程式中注意到了問題，當我旋轉設備時，我看到片段內部的 ViewModel 沒有保存/保留回收器視圖，我不想使用舊方法，比如將資料保存在包中onSaveInstanceState并恢復它，我試過了通過在片段生命周期中的每個方法上列印一些日志來弄清楚為什么會出現這個問題，但我沒有成功
顯示問題的 GIF
視圖模型
@HiltViewModel
class PostViewModel @Inject constructor(
private val mainRepository: MainRepository,
private val dataStoreRepository: DataStoreRepository,
application: Application
) :
AndroidViewModel(application) {
/** ROOM DATABASE */
val readAllPosts: LiveData<List<Item>> = mainRepository.localDataSource.getAllItems().asLiveData()
val postsBySearchInDB: MutableLiveData<List<Item>> = MutableLiveData()
/** RETROFIT **/
var postsResponse: MutableLiveData<NetworkResult<PostList>> = MutableLiveData()
var searchedPostsResponse: MutableLiveData<NetworkResult<PostList>> = MutableLiveData()
var postListResponse: PostList? = null
var postListByLabelResponse: PostList? = null
var searchPostListResponse: PostList? = null
val label = MutableLiveData<String>()
var finalURL: MutableLiveData<String?> = MutableLiveData()
val token = MutableLiveData<String?>()
val currentDestination = MutableLiveData<Int>()
fun getCurrentDestination() {
viewModelScope.launch {
dataStoreRepository.readCurrentDestination.collect {
currentDestination.value = it
}
}
}
val errorCode = MutableLiveData<Int>()
val searchError = MutableLiveData<Boolean>()
var networkStats = false
var backOnline = false
val recyclerViewLayout = dataStoreRepository.readRecyclerViewLayout.asLiveData()
val readBackOnline = dataStoreRepository.readBackOnline.asLiveData()
override fun onCleared() {
super.onCleared()
finalURL.value = null
token.value = null
}
private fun saveBackOnline(backOnline: Boolean) = viewModelScope.launch {
dataStoreRepository.saveBackOnline(backOnline)
}
fun saveCurrentDestination(currentDestination: Int) {
viewModelScope.launch {
dataStoreRepository.saveCurrentDestination(currentDestination)
}
}
fun saveRecyclerViewLayout(layout: String) {
viewModelScope.launch {
dataStoreRepository.saveRecyclerViewLayout(layout)
}
}
fun getPosts() = viewModelScope.launch {
getPostsSafeCall()
}
fun getPostListByLabel() = viewModelScope.launch {
getPostsByLabelSafeCall()
}
fun getItemsBySearch() = viewModelScope.launch {
getItemsBySearchSafeCall()
}
private suspend fun getPostsByLabelSafeCall() {
postsResponse.value = NetworkResult.Loading()
if (hasInternetConnection()) {
try {
val response = mainRepository.remoteDataSource.getPostListByLabel(finalURL.value!!)
postsResponse.value = handlePostsByLabelResponse(response)
} catch (ex: HttpException) {
Log.e(TAG, ex.message ex.cause)
postsResponse.value = NetworkResult.Error(ex.message.toString())
errorCode.value = ex.code()
} catch (ex: NullPointerException) {
postsResponse.value = NetworkResult.Error("There's no items")
}
} else {
postsResponse.value = NetworkResult.Error("No Internet Connection.")
}
}
private suspend fun getPostsSafeCall() {
postsResponse.value = NetworkResult.Loading()
if (hasInternetConnection()) {
try {
if (finalURL.value.isNullOrEmpty()) {
finalURL.value = "$BASE_URL?key=$API_KEY"
}
val response = mainRepository.remoteDataSource.getPostList(finalURL.value!!)
postsResponse.value = handlePostsResponse(response)
} catch (e: Exception) {
postsResponse.value = NetworkResult.Error(e.message.toString())
if (e is HttpException) {
errorCode.value = e.code()
Log.e(TAG, "getPostsSafeCall: errorCode $errorCode")
Log.e(TAG, "getPostsSafeCall: ${e.message.toString()}")
}
}
} else {
postsResponse.value = NetworkResult.Error("No Internet Connection.")
}
}
private fun handlePostsResponse(response: Response<PostList>): NetworkResult<PostList> {
if (response.isSuccessful) {
if (!(token.value.equals(response.body()?.nextPageToken))) {
token.value = response.body()?.nextPageToken
response.body()?.let { resultResponse ->
Log.d(
TAG, "handlePostsResponse: old token is: ${token.value} "
"new token is: ${resultResponse.nextPageToken}"
)
finalURL.value = "${BASE_URL}?pageToken=${token.value}&key=${API_KEY}"
Log.e(TAG, "handlePostsResponse finalURL is ${finalURL.value!!}")
for (item in resultResponse.items) {
insertItem(item)
}
return NetworkResult.Success(resultResponse)
}
}
}
if (token.value == null) {
errorCode.value = 400
} else {
errorCode.value = response.code()
}
return NetworkResult.Error(
"network results of handlePostsResponse ${
response.body().toString()
}"
)
}
private fun handlePostsByLabelResponse(response: Response<PostList>): NetworkResult<PostList> {
if (response.isSuccessful) {
response.body()?.let { resultResponse ->
Log.d(
TAG, "handlePostsByLabelResponse: old token is: ${token.value} "
"new token is: ${resultResponse.nextPageToken}"
)
finalURL.postValue(
(BASE_URL_POSTS_BY_LABEL "posts?labels=${label.value}"
"&maxResults=20"
"&pageToken=")
token.value
"&key=" API_KEY
)
if (postListByLabelResponse == null) {
postListByLabelResponse = resultResponse
} else {
val oldPosts = postListByLabelResponse?.items
val newPosts = resultResponse.items
oldPosts?.addAll(newPosts)
}
return NetworkResult.Success(postListByLabelResponse?:resultResponse)
}
}
if (token.value == null) {
errorCode.value = 400
} else {
errorCode.value = response.code()
}
Log.e(TAG, "handlePostsByLabelResponse: final URL ${finalURL.value}")
return NetworkResult.Error(
"network results of handlePostsByLabelResponse ${
response.body().toString()
}"
)
}
private fun hasInternetConnection(): Boolean {
val connectivityManager = getApplication<Application>().getSystemService(
Context.CONNECTIVITY_SERVICE
) as ConnectivityManager
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
val activeNetwork = connectivityManager.activeNetwork ?: return false
val capabilities =
connectivityManager.getNetworkCapabilities(activeNetwork) ?: return false
return when {
capabilities.hasTransport(NetworkCapabilities.TRANSPORT_WIFI) -> true
capabilities.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR) -> true
capabilities.hasTransport(NetworkCapabilities.TRANSPORT_ETHERNET) -> true
capabilities.hasTransport(NetworkCapabilities.TRANSPORT_VPN) -> true
else -> false
}
} else {
val networkInfo = connectivityManager.activeNetworkInfo
return networkInfo != null && networkInfo.isConnectedOrConnecting
}
}
fun showNetworkStats() {
if (!networkStats) {
Toast.makeText(getApplication(), "No Internet connection", Toast.LENGTH_SHORT).show()
saveBackOnline(true)
} else if (networkStats) {
if (backOnline) {
Toast.makeText(getApplication(), "We're back online", Toast.LENGTH_SHORT).show()
saveBackOnline(false)
}
}
}
private fun insertItem(item: Item) {
viewModelScope.launch(Dispatchers.IO) {
mainRepository.localDataSource.insertItem(item)
}
}
private suspend fun getItemsBySearchSafeCall() {
searchedPostsResponse.value = NetworkResult.Loading()
if (!label.value.isNullOrEmpty()) {
finalURL.value = "${BASE_URL}?labels=${label.value}&maxResults=500&key=$API_KEY"
}
Log.e(TAG, "getItemsBySearch: ${finalURL.value}")
if (hasInternetConnection()) {
try {
val response = mainRepository.remoteDataSource.getPostListBySearch(finalURL.value!!)
searchedPostsResponse.value = handlePostsBySearchResponse(response)
} catch (e: Exception) {
searchedPostsResponse.value = NetworkResult.Error(e.message.toString())
}
} else {
searchedPostsResponse.value = NetworkResult.Error("No Internet Connection.")
}
}
private fun handlePostsBySearchResponse(response: Response<PostList>): NetworkResult<PostList> {
return if (response.isSuccessful) {
val postListResponse = response.body()
NetworkResult.Success(postListResponse!!)
} else {
errorCode.value = response.code()
NetworkResult.Error(response.errorBody().toString())
}
}
fun getItemsBySearchInDB(keyword: String) {
Log.d(TAG, "getItemsBySearchInDB: called")
viewModelScope.launch {
val items = mainRepository.localDataSource.getItemsBySearch(keyword)
if (items.isNotEmpty()) {
postsBySearchInDB.value = items
} else {
searchError.value = true
Log.e(TAG, "list is empty")
}
}
}
}
片段
@AndroidEntryPoint
class AccessoryFragment : Fragment(), MenuProvider, TitleAndGridLayout {
private var _binding: FragmentAccessoryBinding? = null
private val binding get() = _binding!!
private var searchItemList = arrayListOf<Item>()
private lateinit var postViewModel: PostViewModel
private val titleLayoutManager: GridLayoutManager by lazy { GridLayoutManager(context, 2) }
private val gridLayoutManager: GridLayoutManager by lazy { GridLayoutManager(context, 3) }
private var linearLayoutManager: LinearLayoutManager? = null
private val KEY_RECYCLER_STATE = "recycler_state"
private val mBundleRecyclerViewState by lazy { Bundle() }
private lateinit var adapter: PostAdapter
private var isScrolling = false
var currentItems = 0
var totalItems: Int = 0
var scrollOutItems: Int = 0
private var postsAPiFlag = false
private var keyword: String? = null
private lateinit var networkListener: NetworkListener
private var networkStats = false
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
postViewModel = ViewModelProvider(this)[PostViewModel::class.java]
adapter = PostAdapter(this)
postViewModel.finalURL.value =
BASE_URL_POSTS_BY_LABEL "posts?labels=Accessory&maxResults=20&key=$API_KEY"
networkListener = NetworkListener()
}
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View {
_binding = FragmentAccessoryBinding.inflate(inflater, container, false)
val menuHost: MenuHost = requireActivity()
menuHost.addMenuProvider(this, viewLifecycleOwner, Lifecycle.State.CREATED)
postViewModel.label.value = "Accessory"
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
Log.d(TAG, "onViewCreated: called")
postViewModel.recyclerViewLayout.observe(viewLifecycleOwner) { layout ->
linearLayoutManager = LinearLayoutManager(context, LinearLayoutManager.VERTICAL, false)
Log.w(TAG, "onViewCreated getSavedLayout called")
when (layout) {
"cardLayout" -> {
binding.accessoryRecyclerView.layoutManager = linearLayoutManager
adapter.viewType = 0
binding.accessoryRecyclerView.adapter = adapter
}
"cardMagazineLayout" -> {
binding.accessoryRecyclerView.layoutManager = linearLayoutManager
adapter.viewType = 1
binding.accessoryRecyclerView.adapter = adapter
}
"titleLayout" -> {
binding.accessoryRecyclerView.layoutManager = titleLayoutManager
adapter.viewType = 2
binding.accessoryRecyclerView.adapter = adapter
}
"gridLayout" -> {
binding.accessoryRecyclerView.layoutManager = gridLayoutManager
adapter.viewType = 3
binding.accessoryRecyclerView.adapter = adapter
}
}
}
lifecycleScope.launchWhenStarted {
networkListener.checkNetworkAvailability(requireContext()).collect { stats ->
Log.d(TAG, "networkListener: $stats")
postViewModel.networkStats = stats
postViewModel.showNetworkStats()
this@AccessoryFragment.networkStats = stats
if (stats ) {
if (binding.accessoryRecyclerView.visibility == View.GONE) {
binding.accessoryRecyclerView.visibility = View.VISIBLE
}
requestApiData()
} else {
// Log.d(TAG, "onViewCreated: savedInstanceState $savedInstanceState")
noInternetConnectionLayout()
}
}
}
binding.accessoryRecyclerView.onItemClick { _, position, _ ->
val postItem = adapter.differ.currentList[position]
findNavController().navigate(
AccessoryFragmentDirections.actionNavAccessoryToDetailsActivity(
postItem
)
)
}
binding.accessoryRecyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
super.onScrollStateChanged(recyclerView, newState)
if (newState == AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL) {
isScrolling = true
}
}
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
super.onScrolled(recyclerView, dx, dy)
currentItems = linearLayoutManager!!.childCount
totalItems = adapter.itemCount
scrollOutItems = linearLayoutManager!!.findFirstVisibleItemPosition()
if ((!recyclerView.canScrollVertically(1) && dy > 0) &&
(isScrolling && currentItems scrollOutItems >= totalItems && postsAPiFlag)
) {
hideShimmerEffect()
postViewModel.getPostListByLabel()
isScrolling = false
}
}
})
postViewModel.errorCode.observe(viewLifecycleOwner) { errorCode ->
if (errorCode == 400) {
binding.accessoryRecyclerView.setPadding(0, 0, 0, 0)
Toast.makeText(requireContext(), R.string.lastPost, Toast.LENGTH_LONG).show()
binding.progressBar.visibility = View.GONE
} else {
Log.e(TAG, "onViewCreated: ${postViewModel.errorCode.value.toString()} ")
noInternetConnectionLayout()
}
}
}
override fun onConfigurationChanged(newConfig: Configuration) {
super.onConfigurationChanged(newConfig)
Log.d(TAG, "onConfigurationChanged: ${newConfig.orientation}")
Log.d(TAG, "onConfigurationChanged: ${adapter.differ.currentList.toString()}")
Log.d(
TAG,
"onConfigurationChanged: "
binding.accessoryRecyclerView.layoutManager?.itemCount.toString()
)
}
override fun onViewStateRestored(savedInstanceState: Bundle?) {
super.onViewStateRestored(savedInstanceState)
Log.d(TAG, "onViewStateRestored: called")
}
private fun requestApiData() {
showShimmerEffect()
Log.d(TAG, "requestApiData: called")
postViewModel.getPostListByLabel()
postViewModel.postsResponse.observe(viewLifecycleOwner) { response ->
postsAPiFlag = true
when (response) {
is NetworkResult.Success -> {
hideShimmerEffect()
response.data?.let {
binding.progressBar.visibility = View.GONE
// itemArrayList.addAll(it.items)
adapter.differ.submitList(it.items.toList())
}
}
is NetworkResult.Error -> {
hideShimmerEffect()
binding.progressBar.visibility = View.GONE
Log.e(TAG, response.data.toString())
Log.e(TAG, response.message.toString())
}
is NetworkResult.Loading -> {
binding.progressBar.visibility = View.VISIBLE
}
}
}
}
private fun showShimmerEffect() {
binding.apply {
shimmerLayout.visibility = View.VISIBLE
accessoryRecyclerView.visibility = View.INVISIBLE
}
}
private fun hideShimmerEffect() {
binding.apply {
shimmerLayout.stopShimmer()
shimmerLayout.visibility = View.GONE
accessoryRecyclerView.visibility = View.VISIBLE
}
}
private fun changeAndSaveLayout() {
Log.w(TAG, "changeAndSaveLayout: called")
val builder = AlertDialog.Builder(requireContext())
builder.setTitle(getString(R.string.choose_layout))
val recyclerViewLayouts = resources.getStringArray(R.array.RecyclerViewLayouts)
// SharedPreferences.Editor editor = sharedPreferences.edit();
builder.setItems(
recyclerViewLayouts
) { _: DialogInterface?, index: Int ->
try {
when (index) {
0 -> {
adapter.viewType = 0
binding.accessoryRecyclerView.layoutManager = linearLayoutManager
binding.accessoryRecyclerView.adapter = adapter
postViewModel.saveRecyclerViewLayout("cardLayout")
}
1 -> {
adapter.viewType = 1
binding.accessoryRecyclerView.layoutManager = linearLayoutManager
binding.accessoryRecyclerView.adapter = adapter
postViewModel.saveRecyclerViewLayout("cardMagazineLayout")
}
2 -> {
adapter.viewType = 2
binding.accessoryRecyclerView.layoutManager = titleLayoutManager
binding.accessoryRecyclerView.adapter = adapter
postViewModel.saveRecyclerViewLayout("titleLayout")
}
3 -> {
adapter.viewType = 3
binding.accessoryRecyclerView.layoutManager = gridLayoutManager
binding.accessoryRecyclerView.adapter = adapter
postViewModel.saveRecyclerViewLayout("gridLayout")
}
}
} catch (e: Exception) {
Log.e(TAG, "changeAndSaveLayout: " e.message)
Log.e(TAG, "changeAndSaveLayout: " e.cause)
}
}
val alertDialog = builder.create()
alertDialog.show()
}
private fun noInternetConnectionLayout() {
binding.apply {
// accessoryRecyclerView.removeAllViews()
Log.d(TAG, "noInternetConnectionLayout: called")
shimmerLayout.stopShimmer()
shimmerLayout.visibility = View.GONE
accessoryRecyclerView.visibility = View.GONE
}
binding.noInternetConnectionLayout.inflate()
binding.noInternetConnectionLayout.let {
if (networkStats) {
it.visibility = View.GONE
}
}
}
override fun onDestroyView() {
super.onDestroyView()
// adapter.isDestroyed = true
linearLayoutManager?.removeAllViews()
// adView.destroy()
linearLayoutManager = null
_binding = null
}
override fun onDetach() {
super.onDetach()
if(linearLayoutManager != null){
linearLayoutManager = null
}
}
override fun tellFragmentToGetItems() {
if (postViewModel.recyclerViewLayout.value.equals("titleLayout")
|| postViewModel.recyclerViewLayout.value.equals("gridLayout")
) {
hideShimmerEffect()
postViewModel.getPostListByLabel()
}
}
override fun onCreateMenu(menu: Menu, menuInflater: MenuInflater) {
menuInflater.inflate(R.menu.main, menu)
val searchManager =
requireContext().getSystemService(Context.SEARCH_SERVICE) as SearchManager
val searchView = menu.findItem(R.id.app_bar_search).actionView as SearchView
searchView.setSearchableInfo(searchManager.getSearchableInfo(requireActivity().componentName))
searchView.queryHint = resources.getString(R.string.searchForPosts)
searchView.setOnQueryTextListener(object : SearchView.OnQueryTextListener {
override fun onQueryTextSubmit(keyword: String): Boolean {
if (keyword.isEmpty()) {
Snackbar.make(
requireView(),
"please enter keyword to search",
Snackbar.LENGTH_SHORT
).show()
}
// itemArrayList.clear()
this@AccessoryFragment.keyword = keyword
requestSearchApi(keyword)
return false
}
override fun onQueryTextChange(newText: String): Boolean {
return false
}
})
searchView.setOnCloseListener {
if (keyword.isNullOrEmpty()) {
hideShimmerEffect()
return@setOnCloseListener false
}
if (Utils.hasInternetConnection(requireContext())) {
showShimmerEffect()
postViewModel.postListByLabelResponse = null
searchItemList.clear()
// adapter.differ.submitList(ArrayList())
linearLayoutManager?.removeAllViews()
binding.accessoryRecyclerView.removeAllViews()
// itemArrayList.clear()
adapter.differ.submitList(null)
postViewModel.finalURL.value =
BASE_URL_POSTS_BY_LABEL "posts?labels=Accessory&maxResults=20&key=$API_KEY"
requestApiData()
// itemArrayList.clear()
// adapter.submitList(itemArrayList)
//====> Here I call the request api method again
Log.d(
TAG,
"setOnCloseListener: called ${adapter.differ.currentList.size.toString()}"
)
// adapter.notifyDataSetChanged()
// binding.progressBar.visibility = View.GONE
//
Log.d(TAG, "setOnCloseListener: ${postViewModel.finalURL.value.toString()}")
//
// adapter.notifyDataSetChanged()
// }
} else {
Log.d(TAG, "setOnCloseListener: called")
adapter.differ.submitList(null)
searchItemList.clear()
noInternetConnectionLayout()
}
false
}
postViewModel.searchError.observe(viewLifecycleOwner) { searchError ->
if (searchError) {
Toast.makeText(
requireContext(),
"There's no posts with this keyword", Toast.LENGTH_LONG
).show()
}
}
}
private fun requestSearchApi(keyword: String) {
if (Utils.hasInternetConnection(requireContext())) {
showShimmerEffect()
postViewModel.finalURL.value =
"${BASE_URL}?labels=Accessory&maxResults=500&key=$API_KEY"
postViewModel.getItemsBySearch()
postViewModel.searchedPostsResponse.observe(viewLifecycleOwner) { response ->
when (response) {
is NetworkResult.Success -> {
postsAPiFlag = false
// adapter.differ.currentList.clear()
if (searchItemList.isNotEmpty()) {
searchItemList.clear()
}
binding.progressBar.visibility = View.GONE
lifecycleScope.launch {
withContext(Dispatchers.Default) {
searchItemList.addAll(response.data?.items?.filter {
it.title.contains(keyword) || it.content.contains(keyword)
} as ArrayList<Item>)
}
}
Log.d(TAG, "requestSearchApi: test size ${searchItemList.size}")
if (searchItemList.isEmpty()) {
// adapter.differ.submitList(null)
Toast.makeText(
requireContext(),
"The search word was not found in any post",
Toast.LENGTH_SHORT
).show()
hideShimmerEffect()
return@observe
} else {
postsAPiFlag = false
// itemArrayList.clear()
adapter.differ.submitList(null)
hideShimmerEffect()
// Log.d(
//// TAG, "requestSearchApi: searchItemList ${searchItemList[0].title}"
// )
adapter.differ.submitList(searchItemList)
// binding.accessoryRecyclerView.scrollToPosition(0)
}
}
is NetworkResult.Error -> {
hideShimmerEffect()
binding.progressBar.visibility = View.GONE
Toast.makeText(
requireContext(),
response.message.toString(),
Toast.LENGTH_SHORT
).show()
Log.e(TAG, "onQueryTextSubmit: $response")
}
is NetworkResult.Loading -> {
binding.progressBar.visibility = View.VISIBLE
}
}
}
} else {
noInternetConnectionLayout()
}
}
override fun onMenuItemSelected(menuItem: MenuItem): Boolean {
return if (menuItem.itemId == R.id.change_layout) {
changeAndSaveLayout()
true
} else false
}
}
uj5u.com熱心網友回復：
除非我遺漏了一些東西（要經過很多代碼！），否則您不會在配接器上設定任何資料，直到這一點：
private fun requestApiData() {
postViewModel.getPostListByLabel()
postViewModel.postsResponse.observe(viewLifecycleOwner) {
...
adapter.differ.submitList(it.items.toList())
}
并getPostListByLabel()清除當前資料postsResponse
fun getPostListByLabel() = viewModelScope.launch {
getPostsByLabelSafeCall()
}
private suspend fun getPostsByLabelSafeCall() {
postsResponse.value = NetworkResult.Loading()
// fetch data over network and update postsResponse with it later
...
}
因此，當您第一次observe使用它時，它處于NetworkResult.Loading狀態 - 您存盤的所有帖子都已被擦除。
Fragment旋轉和銷毀時會重新創建您的內容Activity-因此，如果您將ViewModel資料內容初始化為該Fragment設定的一部分（就像您在此處所做的那樣），每次重新創建時都會重新初始化Fragment，并且您將丟失當前資料。
您需要想出一種方法來避免這種情況發生——您實際上并不想在Fragment創建 a 時執行清除并獲取，因此您必須決定何時發生。也許在第ViewModel一次創建時（即通過init塊），也許是第一次Fragment呼叫它（例如在VM中創建一個初始化的布林值設定為false，在呼叫中檢查它，在它運行時設定為true ）。或者也許只是在postsResponse還沒有價值的時候（postsResponse.value == null）。我不知道您的應用程式的流程，因此您必須弄清楚何時強制提取以及何時保留已經存在的資料
轉載請註明出處，本文鏈接：https://www.uj5u.com/qiye/507354.html