I have a bunch of integers in an ArrayList. The values are either 1 or 0 at any given time. I have a unique string error message that I would like to display for each of these items if any of the values switch to 1. I have a single textView where I would like to display the current error message if there is one.
For some reason, I cannot understand how to do this. Is there a data structure that I can leverage to solve this problem efficiently?
You can write an anonymous subclass of ArrayList or LinkedList that overrides the set function to do some action whenever a value is changed:
val myList = object: ArrayList<Int>() {
override fun set(index: Int, element: Int): Int {
return super.set(index, element).also { previousElement ->
if (previousElement == 0 && element == 1) {
showErrorMessageForIndex(index)
}
}
}
}
// where showErrorMessageForIndex is a function that sets a message on your text view.
If you do this kind of thing in multiple places in your app, you can generalize it into a reusable class like this:
class MyArrayList<T>(
val onValueChange: (index: Int, oldValue: T, newValue: T)-> Unit
): ArrayList<T>() {
override fun set(index: Int, element: T): T {
return super.set(index, element).also { previousElement ->
if (previousElement != element) {
onValueChange(index, previousElement, element)
}
}
}
}
Then when you create the list, use:
val myList = MyArrayList<Int> { index, oldValue, newValue ->
if (oldValue == 0 && newValue == 1) {
showErrorMessageForIndex(index)
}
}
Updating value of recyclerview but unable to update corresponding data in model class
Model classes
#Parcelize
class GetStockListData : ArrayList<GetStockListDataItem>(), Parcelable
#Parcelize
data class GetStockListDataItem(
var Qty:#RawValue Double,
var selectedQty: Double
): Parcelable
able to change recyclerview element using alertbox as follows
private fun showAlertDialog(stockListData: GetStockListData, position: Int) {
val layoutInflater = LayoutInflater.from(context)
val customView =
layoutInflater.inflate(R.layout.change_qty_dialog, null)
val myBox: android.app.AlertDialog.Builder = android.app.AlertDialog.Builder(context)
myBox.setView(customView)
val dialog = myBox.create()
dialog.show()
val etQuantity = customView.findViewById<AppCompatEditText>(R.id.et_quantity)
if (stockListData[position].Qty < args.getListDetailsByRNumberModelItem.ReqQty) {
val df = DecimalFormat("#.##")
df.roundingMode = RoundingMode.CEILING
etQuantity.setText(df.format(stockListData[position].Qty).toString())
} else
etQuantity.setText(args.getListDetailsByRNumberModelItem.ReqQty.toString())
etQuantity.setSelection(etQuantity.text.toString().length)
etQuantity.requestFocus()
requireContext().showKeyboard()
customView.findViewById<Button>(R.id.btnDone).setOnClickListener {
if(!etQuantity.text.isNullOrEmpty()) {
val qtyStr = etQuantity.text.toString().trim()
var qtyDouble = qtyStr.toDouble()
stockListData[position].selectedQty = qtyDouble
adapter.notifyDataSetChanged()
dialog.dismiss()
}
}
}
for (i in 0 until stockListData.size){
sum += stockListData[i].selectedQty
}
here if user edit Recyclerview list item multiple times, each value added to list. Finally if i try to retrieve sum of all recyclerview elements getting wrong value because in model class values are added when i try to replace element.
Instead of passing whole list as parameter to showAlertDialog() method, you could just pass single item which has to be updated. And one more thing, you should not call adapter.notifyDataSetChanged() for single item updation, rather call adapter.notifyItemChanged(position). Look at below code, I am getting correct sum :
private fun showRecipeMeasureDialog(recipeItem: RecipeItem?,position: Int){
val dialogView = LayoutInflater.from(context).inflate(R.layout.add_recipe_measure_dialog, null)
val dialog = AlertDialog.Builder(context, R.style.RoundedCornersDialog).setView(dialogView).show()
dialog.setCancelable(false)
val displayRectangle = Rect()
val window = activity?.window
window?.decorView?.getWindowVisibleDisplayFrame(displayRectangle)
dialog.window?.setLayout(
(displayRectangle.width() * 0.5f).toInt(),
dialog.window!!.attributes.height
)
context?.resources?.let {
dialogView.findViewById<TextView>(R.id.recipe_measure_title).text = java.lang.String.format(it.getString(R.string.addRecipeMeasure), unitsArray[currentMeasurementUnits - 1])
}
val doneBtn = dialogView.findViewById<ImageButton>(R.id.recipe_measure_done_btn)
val closeBtn = dialogView.findViewById<ImageButton>(R.id.close_btn_add_recipe)
val conversionEditText = dialogView.findViewById<ClearFocusEditText>(R.id.recipe_conversion_tie)
doneBtn.isEnabled = false
if (recipeItem != null ){
conversionEditText.setText("${recipeItem.conversionRatio}")
}
closeBtn.setOnClickListener {
context?.hideKeyboard(it)
dialog.dismiss() }
doneBtn.setOnClickListener {
context?.hideKeyboard(it)
val conversionRatio = conversionEditText.text.toString().toFloat()
if (recipeItem != null){
recipeItem.conversionRatio = conversionRatio
recipeItemList[position] = recipeItem
recipeAdapter.notifyItemChanged(position)
}else{
recipeItemList.add(0,RecipeItem(0,0,conversionRatio,0)) // Use your data class in place of RecipeItem
recipeAdapter.notifyItemInserted(0) // new Item is added to index zero, so adapter has to be updated at index zero
}
// calculating sum
val sum = recipeItemList.map { it.conversionRatio }.sum()
Log.d("tisha==>>","Conversion ratio sum = $sum")
dialog.cancel()
}
}
Problem:
I get 40 items at the beginning of the list, then it starts to count from 11, and after this, everything is good. So, 1...40,11,12,13,...,300.
And when I scroll a lot to the bottom and then scroll up to see first items, the items have been changed to 1,2,...,10,1,2,...,10,1,2,...,10,11,12,...,300.
But, when I pass false to enablePlaceholders in the PagingConfig, when I scroll to the bottom, I see the issue as I said above(1,2,..,40,11,...,300) and suddenly the 40 items vanish and I only see 1,2,...,10 + 11,12,...,300(the correct way); And it doesn't change or get worse again.
ProductsPagingSource:
#Singleton
class ProductsPagingSource #Inject constructor(
private val productsApi: ProductsApi
//private val query: String
) : RxPagingSource<Int, RecyclerItem>() {
override fun loadSingle(params: LoadParams<Int>): Single<LoadResult<Int, RecyclerItem>> {
val position = params.key ?: STARTING_PAGE_INDEX
//val apiQuery = query
return productsApi.getBeersList(position, params.loadSize)
.subscribeOn(Schedulers.io())
.map { listBeerResponse ->
listBeerResponse.map { beerResponse ->
beerResponse.toDomain()
}
}
.map { toLoadResult(it, position) }
.onErrorReturn { LoadResult.Error(it) }
}
private fun toLoadResult(
#NonNull response: List<RecyclerItem>,
position: Int
): LoadResult<Int, RecyclerItem> {
return LoadResult.Page(
data = response,
prevKey = if (position == STARTING_PAGE_INDEX) null else position - 1,
nextKey = if (response.isEmpty()) null else position + 1,
itemsBefore = LoadResult.Page.COUNT_UNDEFINED,
itemsAfter = LoadResult.Page.COUNT_UNDEFINED
)
}
}
ProductsListRepositoryImpl:
#Singleton
class ProductsListRepositoryImpl #Inject constructor(
private val pagingSource: ProductsPagingSource
) : ProductsListRepository {
override fun getBeers(ids: String): Flowable<PagingData<RecyclerItem>> = Pager(
config = PagingConfig(
pageSize = 10,
enablePlaceholders = true,
maxSize = 30,
prefetchDistance = 5,
initialLoadSize = 40
),
pagingSourceFactory = { pagingSource }
).flowable
}
ProductsListViewModel:
class ProductsListViewModel #ViewModelInject constructor(
private val getBeersUseCase: GetBeersUseCase
) : BaseViewModel() {
private val _ldProductsList: MutableLiveData<PagingData<RecyclerItem>> = MutableLiveData()
val ldProductsList: LiveData<PagingData<RecyclerItem>> = _ldProductsList
init {
loading(true)
getProducts("")
}
private fun getProducts(ids: String) {
loading(false)
getBeersUseCase(GetBeersParams(ids = ids))
.cachedIn(viewModelScope)
.observeOn(AndroidSchedulers.mainThread())
.subscribe {
_ldProductsList.value = it
}.addTo(compositeDisposable)
}
}
ProductsListFragment:
#AndroidEntryPoint
class ProductsListFragment : Fragment(R.layout.fragment_product_list) {
private val productsListViewModel: ProductsListViewModel by viewModels()
private val productsListAdapter: ProductsListAdapter by lazy {
ProductsListAdapter(::navigateToProductDetail)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
setupRecycler()
setupViewModel()
}
private fun setupRecycler() {
itemErrorContainer.gone()
productListRecyclerView.adapter = productsListAdapter
}
private fun setupViewModel() {
productsListViewModel.run {
observe(ldProductsList, ::addProductsList)
observe(ldLoading, ::loadingUI)
observe(ldFailure, ::handleFailure)
}
}
private fun addProductsList(productsList: PagingData<RecyclerItem>) {
loadingUI(false)
productListRecyclerView.visible()
productsListAdapter.submitData(lifecycle, productsList)
}
...
BASE_DIFF_CALLBACK:
val BASE_DIFF_CALLBACK = object : DiffUtil.ItemCallback<RecyclerItem>() {
override fun areItemsTheSame(oldItem: RecyclerItem, newItem: RecyclerItem): Boolean {
return oldItem.id == newItem.id
}
override fun areContentsTheSame(oldItem: RecyclerItem, newItem: RecyclerItem): Boolean {
return oldItem == newItem
}
}
BasePagedListAdapter:
abstract class BasePagedListAdapter(
vararg types: Cell<RecyclerItem>,
private val onItemClick: (RecyclerItem, ImageView) -> Unit
) : PagingDataAdapter<RecyclerItem, RecyclerView.ViewHolder>(BASE_DIFF_CALLBACK) {
private val cellTypes: CellTypes<RecyclerItem> = CellTypes(*types)
override fun getItemViewType(position: Int): Int {
getItem(position).let {
return cellTypes.of(it).type()
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
return cellTypes.of(viewType).holder(parent)
}
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
getItem(position).let {
cellTypes.of(it).bind(holder, it, onItemClick)
}
}
}
I had to set the same number for pageSize and initialLoadSize. Also, I had to set the enablePlaceholders to false.
config = PagingConfig(
pageSize = 10,
enablePlaceholders = false,
maxSize = 30,
prefetchDistance = 5,
initialLoadSize = 10
),
But still, I want to know if it's the normal way? If yes, I couldn't find anywhere point to this! If not, why's that? Why initialLoadSize can not have value more than the pageSize?!
As we can see, the default value for the initialLoadSize is:
internal const val DEFAULT_INITIAL_PAGE_MULTIPLIER = 3
val initialLoadSize: Int = pageSize * DEFAULT_INITIAL_PAGE_MULTIPLIER,
Your issue is most likely because at the repository layer your results page numbers are indexed with numbers derived from the total divided by your page size.
This page number scheme assumes that you will page through the items with pages of the same size. However, Paging wants to get an initial page that's three times bigger by default, and then each page should be the page size.
So, the indexes might be like 0 through totalElements/PageSize, with the number for page that includes a given position equaling itemsIndex/PageSize.
This part is especially relevant:
return LoadResult.Page(
data = response,
prevKey = if (position == STARTING_PAGE_INDEX) null else position - 1,
nextKey = if (response.isEmpty()) null else position + 1,
itemsBefore = LoadResult.Page.COUNT_UNDEFINED,
itemsAfter = LoadResult.Page.COUNT_UNDEFINED
)
Let's imagine a pagesize of 10, an initial load of 30, and 100 elements total. We start with page 0, and we request 30 items. Position is 0, and params.loadSize is 30.
productsApi.getBeersList(0, 30)
Then we return a page object with those 30 elements and a nextPage key of 1.
If we imagine all our objects as list, the first page would be the asterisks in this span: [***-------]
Let's get the next page:
productsApi.getBeersList(1, 10)
That returns elements that are this from our span: [-*--------]
And then you get: [--*-------]
So the 0th page is fine, but the 1th and 2nd page overlap with it. Then, pages 3 and onward contain new elements.
Because you're getting the keys for the next and previous pages by adding or subtracting to get the adjacent keys to the current page of the current length, the index can't scale with the page size. This isn't always easy without knowing what is inside the PagingConfig.
However you can make it work with dynamic page sizes if you can guarantee your initial load size is your regular page size times some integer and that you'll always get the requested number of items except for the last page, you could store an offset as your next/previous page keys, and turn that offset into the next page at load like:
/* Value for api pageNo */
val pageNo = (params.key/params.loadSize + STARTING_PAGE_INDEX) ?: STARTING_PAGE_INDEX
productsApi.getBeersList(pageNo, params.loadSize) // and so on
/* for offset keys in PageData */
nextKey = (pageNo + 1) * loadSize
prevKey = (pageNo - 1) * loadSize // Integer division rounds down so larger windows start where they should
I using android.arch.paging.PagedListAdapter <Item, RecyclerView.ViewHolder> and Room DB as data source for show items in RecyclerView.
Each item has date day. I also group elements by this date in override fun onCurrentListChanged(currentList: PagedList<Item>?).
Grouping occurs by dividing into two lists (Items and Dates) with fake positions. Total count is sum items count and dates count.
My problem is an IndexOutOfBoundsException: Inconsistency detected from RecyclerView when refresh or load next items.
Possible solutions: 1 - refuse to separate items (not suitable for my task). 2 - Use notifyDataSetChanged() after submit items (but disappear animation and appear blink update viewHolders).
Can anyone help?
private var fakePositionDates: Map<Int, Date> = emptyMap()
private var fakePositionTaskPositions: Map<Int, Int> = emptyMap()
override fun getItemCount(): Int {
return fakePositionTaskPositions.size + fakePositionDates.size
}
override fun submitList(pagedList: PagedList<Task>?) {
super.submitList(pagedList)
}
override fun onCurrentListChanged(currentList: PagedList<Task>?) {
val groupTasksPositions = currentList?.asIterable()
?.mapIndexed { index, task ->
Pair(index, task.publishDate)
}
?.groupBy { it.second }
?.mapValues {
it.value.map { it.first }
}
?.toSortedMap(Comparator { o1, o2 ->
o2.compareTo(o1)
})
?: sortedMapOf()
val fakePositionDates = mutableMapOf<Int, Date>()
val fakePositionTaskPositions = mutableMapOf<Int, Int>()
var fakePosition = 0
groupTasksPositions.forEach { date, realPositions ->
fakePositionDates[fakePosition] = date
fakePosition += 1
realPositions.forEach {
fakePositionTaskPositions[fakePosition] = it
fakePosition += 1
}
}
this.fakePositionTaskPositions = fakePositionTaskPositions
this.fakePositionDates = fakePositionDates
}
Try to add adapter.submitList(null) and adapter.notifyDataSetChanged in your activity or fragment before you call view model function to refresh your recyclerview
I need to pick a new item from a list that hasn't been picked already until there are no more.
Here is my code:
private var quizQuestionList: ArrayList<Quiz>
private var pickedItems: ArrayList<Int>
private var random: Random = Random()
private fun pickItem(): Quiz {
var index = random?.nextInt(quizQuestionList!!.size)
if (pickedItems.contains(index)) {
index = random?.nextInt(quizQuestionList!!.size)
pickedItems.add(index)
} else {
pickedItems.add(index)
}
val item = quizQuestionList!!.get(index!!)
return item
}
Please suggest any solution that gives me a new item every time. I used an int list for all previously picked items and check every time when picked new item but I didn't get success.
It isn't obvious what you are looking for, but it looks like you want to show different Quiz question from ArrayList. In condition of, when that question is shown, no more same question will be shown. Here is how you should do, I will give you just the logic you could try it yourself:
import java.util.Random
fun main(args: Array<String>) {
val random = Random()
var randomInt: Int
var pickedInt: MutableSet<Int> = mutableSetOf()
fun rand(from: Int, to: Int): Int{
do{
randomInt = random.nextInt(to - from) + from
}while(pickedInt.contains(randomInt))
pickedInt.add(randomInt)
return randomInt
}
while(pickedInt.size < 9){
var differentNumber = rand(1,11)
println(differentNumber)
}
}
This will print nine different Number. The way I choosing MutableSet is because it will only have unique values, no duplicated value. Hope it helps!
here is code for same::
val arrayList = ArrayList<String>()
arrayList.add("a")
arrayList.add("b")
arrayList.add("c")
arrayList.add("d")
arrayList.add("e")
arrayList.add("f")
arrayList.add("g")
arrayList.add("h")
arrayList.add("i")
arrayList.add("j")
arrayList.add("k")
random = Random()
Low = 0
High = arrayList.size
val generateRandom = findViewById<View>(R.id.generateRandom) as Button
generateRandom.setOnClickListener {
val Result = random.nextInt(High - Low) + Low
Log.v("check", arrayList[Result])
}
Please let me know if need more!!
Try this way
class MainActivity : AppCompatActivity() {
private var arrayList = ArrayList<String>()
private var lastItem = -1
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
for (i in 0..9) {
arrayList.add(i.toString())
}
btnData.setOnClickListener {
Log.e("RANDOM_NUMBER", "" + getRandomItemFromList())
}
}
private fun getRandomItemFromList(): Int {
val randomValue = Random().nextInt(arrayList.size)
return if (randomValue != lastItem) {
lastItem = randomValue
randomValue
} else {
getRandomItemFromList()
}
}
}
I made this extension for the ArrayList class in Kotlin you can use it multiple times in only one line.
fun <T> ArrayList<T>.generateRandomItems(numberOfItems: Int): ArrayList<T> {
val range = if(numberOfItems > this.size){this.size}else{numberOfItems}
val randomItems = ArrayList<T>()
for (i in 0..range) {
var randomItem: T
do {
randomItem = this.random()
} while (randomItems.contains(randomItem))
randomItems.add(randomItem)
}
return randomItems
}
Usage:
val randomUsersList = usersList.generateRandomItems(20)
Note: the usersList is the list that has items to generate random items from.