Develop Reference

My recyclerview resets when I add or delete an item from a Table (with Room) in Kotlin

First of all, I am Spanish so my english is not good.
I have an app with Kotlin and room, and it has a Recyclerview.
I have 3 tables: coaster, user and favorite.
The user can add coasters to favorite, and this is done succesfully.
The problem that I have is that when the user clicks on the button to add or delete from favorites, the recyclerview resets, it displays again. So it scrolls to the top of the Screen, and also some odd spaces appears after the element.
I also have a function to search, and it happens the same: spaces appears after each element when I am searching.
I have tried everything: notifyItemChanged,
notifyDataSetChanged... it doesnt work! I also tried removing the observer once from the recyclerview...
My main activity:
class CoasterFragment : Fragment() {
lateinit var coasterListener: CoasterListener
lateinit var usuarioCoaster: List\<UsuarioCoaster\>
private lateinit var searchView: SearchView
private lateinit var cAdapter: CoasterRecyclerViewAdapter
private var \_binding: FragmentCoasterBinding? = null
private val binding get() = \_binding!!
private val viewModel: CoastersViewModel by viewModels()
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View {
_binding = FragmentCoasterBinding.inflate(inflater, container, false)
val root: View = binding.root
/* val livedata = viewModel.coasters()
livedata.observe(viewLifecycleOwner,object: Observer <List<CoasterFavorito>> {
override fun onChanged(it: List<CoasterFavorito>) {
createRecyclerView(it)
livedata.removeObserver(this)
}
})*/
viewModel.coasters().observe(viewLifecycleOwner){createRecyclerView(it)}
coasterListener = CoasterListenerImpl(requireContext(), viewModel)
searchView = binding.search
searchView.clearFocus()
searchView.setOnQueryTextListener(object: SearchView.OnQueryTextListener{
override fun onQueryTextSubmit(query: String?): Boolean {
if(query != null){
searchDatabase(query)
}
return true
}
override fun onQueryTextChange(query: String?): Boolean {
if(query != null){
searchDatabase(query)
}
return true
}
})
return root
}
fun createRecyclerView(coasters: List<CoasterFavorito>) {
cAdapter =
CoasterRecyclerViewAdapter(
coasters as MutableList<CoasterFavorito>,
coasterListener,
requireContext()
)
val recyclerView = binding.recyclerCoaster
recyclerView.apply {
layoutManager = LinearLayoutManager(context, RecyclerView.VERTICAL, false)
adapter = cAdapter
addItemDecoration(DividerItemDecoration(context, RecyclerView.VERTICAL))
cAdapter.notifyDataSetChanged()
}
}
fun searchDatabase(query: String) {
val searchQuery = "%$query%"
viewModel.searchDatabase(searchQuery).observe(viewLifecycleOwner) { createRecyclerView(it)
}
}
override fun onDestroyView() {
super.onDestroyView()
_binding = null
}
}
my adapter:
class CoasterRecyclerViewAdapter(val coasters: List<CoasterFavorito>, val listener: CoasterListener,
val context: Context, ) : RecyclerView.Adapter<CoasterRecyclerViewAdapter.ViewHolder>(){
class ViewHolder private constructor(val binding: CoasterItemBinding, private val listener: CoasterListener,
private val context: Context): RecyclerView.ViewHolder(binding.root){
fun relleno(data: CoasterFavorito){
binding.nombre.text = data.coaster.nombre
binding.parque.text = data.coaster.parque
binding.ciudad.text = data.coaster.ciudad
binding.provincia.text = data.coaster.provincia
binding.comunidad.text = data.coaster.comunidadAutonoma
Glide
.with(context)
.load(data.coaster.imagen)
.centerCrop()
.into(binding.imagen)
binding.check.isChecked = data.favorito
binding.check.setOnClickListener{
if (data.favorito) {
listener.delFavorito(data.coaster.id)
binding.check.isChecked = false
} else {
listener.addFavorito(data.coaster.id)
binding.check.isChecked = true
}
}
}
companion object{
fun crearViewHolder(parent: ViewGroup, listener: CoasterListener, adapter: CoasterRecyclerViewAdapter, context: Context):ViewHolder{
val layoutInflater = LayoutInflater.from(parent.context)
val binding = CoasterItemBinding.inflate(layoutInflater, parent, false)
return ViewHolder(binding, listener, context )
}
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) = ViewHolder.crearViewHolder(parent, listener, this, context)
override fun onBindViewHolder(holder: ViewHolder, position: Int) = holder.relleno(coasters[position])
override fun getItemCount() = coasters.size
}
interface CoasterListener {
fun addFavorito(id: Long)
fun delFavorito(id: Long)
}
I have tried everything: notifyItemChanged,
notifyDataSetChanged... it doesnt work! I also tried removing the observer once from the recyclerview...

Your createRecyclerView function should be invoked only once in a whole lifecycle of the Fragment. You should not create any new RecyclerView.Adapter, or set a LayoutManager to the RecyclerView every time your data set changes.
Therefore the Observer used in viewModel.coasters.observe() should only submit a new List to the existing Adapter and call .notifyDataSetChanged(), or other notifying functions.

Textview dispalys "androidx.livecycle.CoroutineLiveData"

I want to display the sum of a column from my room database in a textview.
After implementing my Query and setting the text of the Textview, it displays the following:
androidx.lifecycle.CoroutineLiveData#76f6edd
Any idea why this happens? Is it because my Query does not work or my way of implementign it is wrong?
It is my first time ever of actually programming. I know probably most of my code is not 100% correct, but I am working on it.
The Query from my Dao:
#Query("SELECT SUM(total)AS sum_total FROM receipt_table")
fun getSum(): Flow<Float>
The Fragment:
#AndroidEntryPoint
class HistoryFragment : Fragment(R.layout.fragment_history) {
private val viewModel: PurchaseViewmodel by viewModels()
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_history, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val binding = FragmentHistoryBinding.bind(view)
val exampleAdapter = ExampleAdapter()
binding.apply{
recyclerView.apply{
layoutManager = LinearLayoutManager(requireContext())
adapter = exampleAdapter
}
totalSumTextView.apply {
val totalSum = viewModel.totalSum
text = totalSum.toString()
}
ItemTouchHelper(object : ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT) {
override fun onMove(
recyclerView: RecyclerView,
viewHolder: RecyclerView.ViewHolder,
target: RecyclerView.ViewHolder
): Boolean {
return false
}
override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
val receipt = exampleAdapter.currentList[viewHolder.adapterPosition]
viewModel.onSwipe(receipt)
}
}).attachToRecyclerView(recyclerView)
}
setFragmentResultListener("add_receipt_request"){_,bundle ->
val result = bundle.getInt("add_receipt_request")
viewModel.onAddResult(result)
}
viewModel.receipts.observe(viewLifecycleOwner){
exampleAdapter.submitList(it)
}
viewLifecycleOwner.lifecycleScope.launchWhenStarted {
viewModel.addTaskEvent.collect { event->
when(event){
is PurchaseViewmodel.TasksEvent.ShowUndoDelete -> {
Snackbar.make(requireView(),"Tasks deleted", Snackbar.LENGTH_LONG)
.setAction("UNDO"){
viewModel.unDoDeleteClick(event.receipts)
}.show()
}
}
}
}
}
}
And the Viewmodel:
#HiltViewModel
class PurchaseViewmodel #Inject constructor(
private val receiptDao: ReceiptDao
): ViewModel() {
private val tasksEventChannel = Channel<TasksEvent>()
val addTaskEvent = tasksEventChannel.receiveAsFlow()
val receipts = receiptDao.getAllReceipts().asLiveData()
val totalSum = receiptDao.getSum().asLiveData()
fun onAddResult(result: Int){
when (result){
ADD_RECEIPT_RESULT_OK ->showReceiptSavedConfirmation("Receipt has been saved")
}
}
private fun showReceiptSavedConfirmation (text: String) = viewModelScope.launch {
tasksEventChannel.send(TasksEvent.ShowReceiptSavedConfirmation(text))
}
fun onSwipe (receipts: Receipts) = viewModelScope.launch {
receiptDao.delete(receipts)
tasksEventChannel.send(TasksEvent.ShowUndoDelete(receipts))
}
fun unDoDeleteClick (receipts: Receipts) = viewModelScope.launch {
receiptDao.insert(receipts)
}
sealed class TasksEvent {
data class ShowReceiptSavedConfirmation(val msg: String) : TasksEvent()
data class ShowUndoDelete(val receipts: Receipts) : TasksEvent()
}
}

You are getting a LiveData object here, not just a value:
val totalSum = receiptDao.getSum().asLiveData()
When you call:
totalSum.toString()
It calls toString method on the LiveData object that the reason, why you have "androidx.lifecycle.CoroutineLiveData#76f6edd" inside your TextView.
To fix the issue, just replace:
totalSumTextView.apply {
val totalSum = viewModel.totalSum
text = totalSum.toString()
}
with:
viewModel.totalSum.observe(this) { totalSumTextView.text = it}
Detailed review, how to work with a LiveData you can find here:
https://developer.android.com/topic/libraries/architecture/livedata

Algolia Android - Empty query not being filtered out

I'm attempting to set my search box to not return any search results when the query is empty - i.e. when nothing has been typed in the box. Algolia InstantSearch by default returns all entries to scroll through which are then filtered as the user searches.
I followed the API docs on aloglia's website for removing the empty query but my search box still returns all entries. I'm a little stuck since it seems to be a very straightforward class, but using the default SearchBoxView vs my amended version NoEmptySearchBox makes no difference in results.
Here's GroupFragment where I'm calling the SearchBoxView:
class GroupFragment : Fragment() {
private val connection = ConnectionHandler()
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.group_fragment, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val viewModel = ViewModelProviders.of(requireActivity())[SearcherViewModel::class.java]
val searchBoxView = NoEmptySearchBox(searchView)
viewModel.groups.observe(this, Observer { hits -> viewModel.adapterProduct.submitList(hits) })
connection += viewModel.searchBox.connectView(searchBoxView)
groupList.let {
it.itemAnimator = null
it.adapter = viewModel.adapterProduct
it.layoutManager = LinearLayoutManager(requireContext())
it.autoScrollToStart(viewModel.adapterProduct)
}
}
override fun onDestroyView() {
super.onDestroyView()
connection.disconnect()
}
}
And here's my NoEmptySearchBox class, which implements SearchBoxView:
class NoEmptySearchBox (
val searchView: SearchView
) : SearchBoxView {
override var onQueryChanged: Callback<String?>? = null
override var onQuerySubmitted: Callback<String?>? = null
init {
searchView.setOnQueryTextListener(object : SearchView.OnQueryTextListener {
override fun onQueryTextSubmit(query: String?): Boolean {
query?.isNotEmpty()?.let { onQuerySubmitted?.invoke(query) }
return false
}
override fun onQueryTextChange(query: String?): Boolean {
query?.isNotEmpty()?.let { onQuerySubmitted?.invoke(query) }
return false
}
})
}
override fun setText(text: String?, submitQuery: Boolean) {
searchView.setQuery(text, false)
}
}
And here's my SearcherViewModel:
class SearcherViewModel : ViewModel() {
val client = ClientSearch(ApplicationID("APP_ID"), APIKey("API_KEY"), LogLevel.ALL)
val index = client.initIndex(IndexName("groups"))
val searcher = SearcherSingleIndex(index)
override fun onCleared() {
super.onCleared()
searcher.cancel()
connection.disconnect()
}
val dataSourceFactory = SearcherSingleIndexDataSource.Factory(searcher) { hit ->
Group(
hit.json.getPrimitive("course_name").content,
hit.json.getObjectOrNull("_highlightResult")
)
}
val pagedListConfig = PagedList.Config.Builder().setPageSize(50).build()
val groups: LiveData<PagedList<Group>> = LivePagedListBuilder(dataSourceFactory, pagedListConfig).build()
val adapterProduct = GroupAdapter()
val searchBox = SearchBoxConnectorPagedList(searcher, listOf(groups))
val connection = ConnectionHandler()
init {
connection += searchBox
}
}

Show API response on fragment on submit

When I search on my searchview I want to send the search value to the api that will give back a response that I want to be showed on the fragment. So when I submit my search I want to show the fragment with the response! I tried to make a function to render the fragment but I think im doing it completly wrong...
Im begginer and this is for a project for school, thank you for help!
SearchView
override fun onCreateOptionsMenu(menu: Menu): Boolean {
// Inflate the menu; this adds items to the action bar if it is present.
menuInflater.inflate(R.menu.main, menu)
val manager = getSystemService(Context.SEARCH_SERVICE) as SearchManager
val searchItem = menu.findItem(R.id.action_search)
val searchView = searchItem?.actionView as SearchView
searchView.setSearchableInfo(manager.getSearchableInfo(componentName))
searchView.setOnQueryTextListener(object: SearchView.OnQueryTextListener{
override fun onQueryTextSubmit(query: String?): Boolean {
searchView.clearFocus()
searchView.setQuery("",false)
searchItem.collapseActionView()
return true
}
override fun onQueryTextChange(newText: String?): Boolean {
return false
}
})
return true
}
Data Class
data class SearchPost(val searchKey: String)
Fragment
class SendFragment : Fragment() {
var newList: MutableList<News> = mutableListOf<News>()
companion object {
fun newInstance() = SendFragment()
}
private lateinit var viewModel: SendViewModel
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_searched, container, false)
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
viewModel = ViewModelProviders.of(this).get(SendViewModel::class.java)
recyclerView.setHasFixedSize(true)
recyclerView.layoutManager = LinearLayoutManager(this.context)
// TODO: Use the ViewModel
val searchedObserver = Observer<List<News>>
{
// Access the RecyclerView Adapter and load the data into it
newList -> recyclerView.adapter = NewsAdapter(newList,this.context!!)
}
viewModel.getNewSearched().observe(this, searchedObserver)
}
}
Fragment View Model
class SendViewModel : ViewModel() {
// TODO: Implement the ViewModel
private var newList: MutableLiveData<List<News>> = MutableLiveData()
fun getNewSearched(): MutableLiveData<List<News>>
{
searchedNew()
return newList;
}
private fun searchedNew()
{
val retrofit = Retrofit.Builder()
.baseUrl("http://192.168.1.78:3000")
.addConverterFactory(GsonConverterFactory.create())
.build()
val api = retrofit.create(ApiService::class.java)
val searchPost = SearchPost("this is want to be the query")
api.sendSearch(searchPost).enqueue(object : Callback<List<News>> {
override fun onResponse(call: Call<List<News>>, response: Response<List<News>>) {
newList.value=(response.body()!!)
}
override fun onFailure(call: Call<List<News>>, t: Throwable) {
Log.d("fail", "onFailure:")
}
})
}
}
Api interface
interface ApiService {
#POST("/search")
fun sendSearch(#Body searchPost: SearchPost): Call<List<News>>
}

Observe view model like this :
viewModel.getNewSearched().observe(this, Observer<MutableList<List<News>>> {
myNewsData ->
Log.d("print my data", myNewsData) // first try to print this data whether data is coming or not
recyclerView.adapter = NewsAdapter( myNewsData ,this.context!!)
})
Initialize your searchView :
private fun initSearchView() {
search_view.setOnQueryTextListener(object :
androidx.appcompat.widget.SearchView.OnQueryTextListener {
override fun onQueryTextSubmit(newText: String?): Boolean {
viewMode.getNewSearched() // call your api here
return false // don,t change it to true
}
override fun onQueryTextChange(query: String?): Boolean {
return false
}
})
}
At last I thing you should pass the text to viewmodel which you want to search
override fun onQueryTextSubmit(query: String?): Boolean {
viewMode.getNewSearched(query)
In side viewmodel :
fun getNewSearched(textYouWantToSearch :String): MutableLiveData<List<News>>
{
searchedNew(textYouWantToSearch) // same pass in searchedNew() else your data class is always blank
return newList;
}
In my understanding your data class which you are passing in your retrofit call is always blank because you are not passing any value from anywhere you should use query string of your search method and try to pass as an parameter.

Save/Restore Fragment state with RecyclerView in Android

I have created an Android app, which connects to GitHub API and shows a list of repositories of certain user. List is shown by recyclerView. I'm trying to save and restore a list, when I'm switching fragments. I have tried to save a list to a variable and add this to recyclerView. But it doesn't work.
My Fragment:
class MainFragment : Fragment() {
lateinit var recyclerView: RecyclerView
var responseSave:List<GitHubPOJO> = ArrayList()
var posts: MutableList<GitHubPOJO> = ArrayList()
lateinit var btn:Button
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
val view = inflater.inflate(R.layout.fragment_main, container, false)
btn = view.findViewById(R.id.button)
btn.setOnClickListener {
posts = ArrayList()
val name:String = view!!.findViewById<EditText>(R.id.editText).text.toString()
recyclerView = view!!.findViewById(R.id.posts_recycle_view)
val layoutManager = LinearLayoutManager(this.activity!!)
recyclerView.layoutManager = layoutManager
val adapter = PostsAdapter(posts)
recyclerView.adapter = adapter
//HIDE KEYBOARD
val inputMethodManager = this.activity!!.getSystemService(Activity.INPUT_METHOD_SERVICE) as InputMethodManager
if(activity!!.currentFocus !=null) {
inputMethodManager.hideSoftInputFromWindow(this.activity!!.currentFocus!!.windowToken, 0)
}
val service = Retrofit.Builder()
.baseUrl("https://api.github.com/") // CHANGE API
.addConverterFactory(GsonConverterFactory.create())
.build()
.create(GitHubService::class.java)
service.retrieveRepositories(name)
.enqueue(object : Callback<List<GitHubPOJO>> {
override fun onResponse(call: Call<List<GitHubPOJO>>, response: Response<List<GitHubPOJO>>) {
responseSave = response.body()!!
posts.addAll(responseSave)
response.body()?.forEach { println ("TAG_: $it")}
recyclerView.adapter?.notifyDataSetChanged()
}
override fun onFailure(call: Call<List<GitHubPOJO>>, t: Throwable) {
//Toast.makeText(this#MainFragment, "Error occurred while networking", Toast.LENGTH_SHORT).show()
}
})
recyclerView.addOnItemTouchListener(
ClickListener(this.activity!!, recyclerView, object : ClickListener.OnItemClickListener {
override fun onLongItemClick(view: View?, position: Int) {
}
override fun onItemClick(view: View, position: Int) {
val url = posts!![position].htmlUrl
println("URL = $url")
view.findNavController().navigate(MainFragmentDirections.actionMainFragmentToWebFragment(url))
}
})
)
}
return view
}
And there is my code onResume:
override fun onResume() {
super.onResume()
val adapter = PostsAdapter()
adapter.updateAdapterList(responseSave.toMutableList())
println("RESUME")
println(responseSave)
}
When I print responseSave I see that my list is there. But it doesn't appears in RecyclerView.
Fragments are swithced by standart navigation library.
Activity code:
class MainActivity : AppCompatActivity(){
private lateinit var navController: NavController
private lateinit var mNavView:NavigationView
private lateinit var mDrawerLayout:DrawerLayout
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
mDrawerLayout = findViewById(R.id.drawer_layout)
mNavView = findViewById(R.id.nav_view)
navController = this.findNavController(R.id.myNavHostFragment)
NavigationUI.setupActionBarWithNavController(this, navController,mDrawerLayout)
NavigationUI.setupWithNavController(mNavView, navController)
}
override fun onSupportNavigateUp(): Boolean {
val navController = this.findNavController(R.id.myNavHostFragment)
return NavigationUI.navigateUp(mDrawerLayout,navController)
}}
My RecyclerView Adapter code:
class PostsAdapter(private var posts: MutableList<GitHubPOJO>? = ArrayList()) : RecyclerView.Adapter<PostsAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val v = LayoutInflater.from(parent.context).inflate(R.layout.post_item, parent, false)
return ViewHolder(v)
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
val post = posts!![position]
holder.post.text = post.name
holder.site.text = post.fullName // Change what you wanna see
}
fun updateAdapterList(newList: MutableList<GitHubPOJO>) {
posts!!.clear()
posts!!.addAll(newList)
notifyDataSetChanged()
}
override fun getItemCount(): Int {
return posts?.size ?: 0
}
inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
var post: TextView = itemView.findViewById<View>(R.id.postitem_post) as TextView
var site: TextView = itemView.findViewById<View>(R.id.postitem_site) as TextView
}}

Add a method in your adapter thats something like;
fun updateAdapterList(newList: MutableList<GitHubPOJO>) {
oldList.clear()
oldList.addAll(newList)
notifyDataSetChanged()
}
Then call this in your onResume() and pass in your updated list

The problem is on your onResume method. You are not adding an Adapter and a LayoutManager to the RecylerView so it can't display the data. Try moving the RecylerView initalization code from the onClickListener to your onResume method:
recyclerView = view!!.findViewById(R.id.posts_recycle_view)
val layoutManager = LinearLayoutManager(this.activity!!)
recyclerView.layoutManager = layoutManager
val adapter = PostsAdapter(posts)
recyclerView.adapter = adapter
Although having this initialization code in your onCreateView method would be better since it's the first lifecycle method called when a fragment returns to the front view from the backstack.