android-fragments 配置更改(设备轮换)时，ViewModel未保存recyclerview数据

31moq8wy  于 2022-11-13  发布在  Android
关注(0)|答案(1)|浏览(147)

我刚刚注意到我的应用程序中的问题，当我旋转设备时，我看到片段内的ViewModel不保存/保留回收器视图，我不想使用旧方法，如将数据保存在捆绑包onSaveInstanceState中并恢复它，我试图通过在片段生命周期中打印每个方法的一些日志来找出此问题的原因，但我没有成功

显示问题的GIF

视图模型

@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")
            }

        }
    }

}

"碎片"

@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
    }

}
android-fragments

1条答案

按热度按时间
oipij1gg

oipij1gg1#

除非我遗漏了什么（这需要执行大量代码！），否则不要在适配器上设置任何数据，直到这一位：

private fun requestApiData() {
    postViewModel.getPostListByLabel()
    postViewModel.postsResponse.observe(viewLifecycleOwner) {
        ...
        adapter.differ.submitList(it.items.toList())
}

并且getPostListByLabel()清除postsResponse中的当前数据

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，当您第一次使用observe时，它处于NetworkResult.Loading状态-您存储的任何帖子都已被擦除。
当Activity被旋转和销毁时，Fragment会被重新创建--因此，如果您在Fragment设置过程中初始化ViewModel数据内容（就像您在这里所做的），那么每次重新创建Fragment时，它都会被重新初始化，您将丢失当前数据。
您需要找到一种方法来避免这种情况的发生--您实际上并不希望在创建Fragment时执行清除和获取操作，因此您必须决定它 * 应该 * 在什么时候发生。（例如，通过init块），可能是Fragment * 第一次 * 调用它（例如，在VM中创建一个 * initialized * 布尔值，将其设置为 false，在调用中检查它，我不知道您的应用程序的流程，因此您必须计算出何时强制获取数据以及何时保留已经存在的数据。

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