Develop Reference

mutableStateListOf change not reflecting in UI - Jetpack Compose

in my ViewModel:
private val _itemList = mutableStateListOf<Post>()
val itemList: List<Post> = _itemList
fun likePost(newPost: Post){
val index = _itemList.indexOf(newPost)
_itemList[index] = _itemList[index].copy(isLiked = true)
}
Here my Post data class:
data class Post(
val id: Int,
val name: String,
val isLiked: Boolean = false,
)
And here my Composable:
val postList = viewModel.itemList
LazyRow(content = {
items(postList.size) { i ->
val postItem = postList[i]
PostItem(
name = postItem.name,
isLiked = postItem.isLiked,
likePost = { viewModel.likePost(postItem)}
)
}
})
The change does not update in the UI instantly, I first have to scroll the updated item out of the screen so it recomposes or switch to another Screen and go back to see the change.

For some reason it doesn't like updating, it will add and delete and update instantly. You have to do it this way when updating for our to update the state.
fun likePost(newPost: Post){
val index = _itemList.indexOf(newPost)
_itemList[index] = _itemList[index].copy()
_itemList[index].isLiked = true
}

You are returning a List<> effectively and not MutableStateList from your ViewModel.
If you want the list to not be mutable from the view, I happen to use MutableStateFlow<List<>> and return StateFlow<List<>>. You could also just convert it to a list in your composable.
Edit:
//backing cached list, or could be data source like database
private val deviceList = mutableListOf<Device>()
private val _deviceListState = MutableStateFlow<List<Device>>(emptyList())
val deviceListState: StateFlow<List<BluetoothDevice>> = _deviceListState
//manipulate and publish
fun doSomething() {
_deviceListState.value = deviceList.filter ...
}
In your UI
val deviceListState = viewModel.deviceListState.collectAsState().value

How to use SetOnClickListener on a programmatic ScrollView Android Kotlin

I created a scrollView programmaticaly that contains 20 views each with an image and a text.
I have two questions :
1 - is the id assignment correct and is my setOnClickListener correct?
2 - By which method onClick can I know which view of the scrollView the user has clicked?
See my code below
private var integerList: MutableList<Int>? = mutableListOf()
private var cellNo: MutableList<String>? = mutableListOf()
private var sv_mvmtChoosed = ""
private fun showSpinner() {
/* SCROllL VIEW */
var linearLayout: LinearLayout? = null
linearLayout = findViewById(R.id.linear1)
val layoutInflater = LayoutInflater.from(this)
var randIndex = 0
for (posIndex in 0..19) {
val rand = Random()
randIndex = rand.nextInt(20)
while (integerList!!.contains(randIndex)) {
randIndex = rand.nextInt(20)
}
integerList!!.add(randIndex)
// Create the view...
val view: View = layoutInflater.inflate(R.layout.scroll_bckgrnd, linearLayout, false)
// give it an id
view.id = generateViewId()
view.setOnClickListener(this)
cellNo!!.add(view.id.toString())
println(cellNo)
//... then populate it with image and text
val iv = view.findViewById<ImageView>(R.id.iv)
iv.setImageResource(sv_photoImage[randIndex])
val tv = view.findViewById<TextView>(R.id.tv)
tv.text = sv_photoName[randIndex]
linearLayout?.addView(view)
}
// which view the user did select?
fun onClick(view: View?) {
when (view!!.id) {
??? -> doSomething
}
}
}
Any idea to get me back on track will be welcome.

Its probably better to make a new OnClickListener for every view.
view.setOnClickListener(this)
needs to be this
view.setOnClickListener {
// do something
}
or
view.setOnClickListener(createOnClickListner())
fun createOnClickListner():View.OnClickListener{
return object :View.OnClickListener{
override fun onClick(view : View) {
//do something with the view that was clicked
}
}
}

Thanks a lot avalerio.
I finally found a solution as follow :
I replaced :
// give it an id
view.id = generateViewId()
view.setOnClickListener(this)
cellNo!!.add(view.id.toString())
println(cellNo)
with :
// give it an id
view.id = posIndex
view.setOnClickListener(this)
then I did this :
// the onClickListener for my 20 images/text
override fun onClick(view: View?) {
when (view!!.id) {
// Now de position clicked on the ScrollView
in 0..19 -> didHeSucceeded(view!!.id)
}
}
And use the result:
private fun didHeSucceeded(scrllPos: Int) {
// TODO: close de scrollView, how ? :-)
spinnerChoice = nameOfTechScrollVw[scrllPos]
succes = (!allreadyChoosedArray.contains(spinnerChoice)) && (currentArray.contains(spinnerChoice
))
if (succes) {
...
...
}
It works perfectly

Kotlin - Get new index of item in shuffled list

I have a multiple choice quiz with 4 choices per answer. In the ArrayList with the questions and choices, the correct answer is set to the index of the correct option. I want to shuffle the choices but am not sure how to identify the new index of the correct answer. Any thoughts?
Question object
object ConstantsAnalysis {
const val TOTAL_CORRECT: String = "total_correct"
const val TOTAL_OPP: String = "total_opp"
fun getQuestions3(): ArrayList<Questions3> {
val questionList = ArrayList<Questions3>()
val q1 = Questions3(1, null,
"On a graph, the horizontal line along which data are plotted is the _____",
"y axis", "x axis", "origin", "quadrant", 2, R.string.Jones_1995, null)
questionList.addAll(listOf(q1))
questionList.shuffle()
return questionList
}
}
Data class
data class Questions3(
val id: Int, val image: Int?, val question: String, val option1: String, val option2: String,
val option3: String, val option4: String, val correctAnswer: Int, val dialogBox: Int?, val dialogBox2: Int?)
Shuffle choices
val ansorder = arrayOf(question.option1, question.option2, question.option3, question.option4)
ansorder.shuffle()
radio_button1.text = ansorder[0]
radio_button2.text = ansorder[1]
radio_button3.text = ansorder[2]
radio_button4.text = ansorder[3]
Check answer choice
if (questions3!!.correctAnswer != mSelectedOptionPosition) {
//do x
}
Edit (Since correct answer is a string and the index changes after shuffling, answerView(questions3.correctAnswer, R.drawable.correct_option_border.
class QuestionsActivityAnalysis : AppCompatActivity(), View.OnClickListener {
private var mCurrentPosition:Int = 1
private var mQuestionsList:ArrayList<Questions3>? = null
private var mSelectedOptionPosition:Int = 0
private var mCorrectAnswers: Int = 0
private var mSelectedOptionText: String? = null
private fun shuffle() {
val question = mQuestionsList!![mCurrentPosition - 1]
val ansorder = arrayOf(question.option1, question.option2, question.option3, question.option4)
ansorder.shuffle()
radio_button1.text = ansorder[0]
radio_button2.text = ansorder[1]
radio_button3.text = ansorder[2]
radio_button4.text = ansorder[3]
}
override fun onClick(v: View?) {
when(v?.id){
R.id.radio_button1 -> { selectedOptionView(radio_button1, 1)
mSelectedOptionText = radio_button1.text as String?
}
R.id.radio_button2 -> { selectedOptionView(radio_button2, 2)
mSelectedOptionText = radio_button2.text as String?
}
R.id.radio_button3 -> { selectedOptionView(radio_button3, 3)
mSelectedOptionText = radio_button3.text as String?
}
R.id.radio_button4 -> { selectedOptionView(radio_button4, 4)
mSelectedOptionText = radio_button4.text as String?
}
R.id.btn_submit -> {
val questions3 = mQuestionsList?.get(mCurrentPosition - 1)
if (questions3!!.correctAnswer != mSelectedOptionText) {
} else {
mCorrectAnswers++
}
answerView(questions3.correctAnswer, R.drawable.correct_option_border)
private fun answerView(answer: Int, drawableView: Int) {
when(answer){
1 -> {
radio_button1.background = ContextCompat.getDrawable(this, drawableView)
}
2 -> {
radio_button2.background = ContextCompat.getDrawable(this, drawableView)
}
3 -> {
radio_button3.background = ContextCompat.getDrawable(this, drawableView)
}
4 -> {
radio_button4.background = ContextCompat.getDrawable(this, drawableView)
}
}
}

I would really recommend just creating a data class like this:
data class QuestionOption(val question:String, val isCorrect = false)
Afterwards you can shuffle any way you like and just check if the selected QuestionOption has isCorrect set to true. You get a bunch of benefits and the logic gets simpler.
Edit:
To make it easier to declare questions this way:
In general if you add questions in your code you want only as much necessary code as required. For this you can either declare a good constructor or a function that basically maps your values to a constructor. In your case I'd say
data class Questions3(
val id: Int, val question: String, val option1: String, val option2: String,
val option3: String, val correctOption: String, val image: Int?=null,val dialogBox1: Int?=null,val dialogBox2: Int?=null)
(notice how the optional parameters are last, you don't need to specify them as well thanks to them beeing null by default)
Makes sense, in theory you could also (not too clean but easy) just shuffle option 1-3 & correctOption and then just compare if the correctOption String matches the selected String.
Otherwise as I said, you can always create logic for mapping stuff. Here you can either map from Constructor to another Constructor, same with Functions that return a finished Object.

Get the returned list from firestore based on condition when a value is passed to firestore function

I am trying to return a list from inside firestore function based on if a condition is true.I want to return different lists when different categories are selected.
I tried:
putting the return statement out of firestore function which did not work and returned empty list due to firestore async behaviour.
creating my own callback to wait for Firestore to return the data using interface as I saw in some other questions but in that case how am i supposed to access it as my function has a Int value(i.e.private fun getRandomPeople(num: Int): List<String>)?
What could be the way of returning different lists for different categories based on firestore conditions?
My code(Non Activity class):
class Board// Create new game
(private val context: Context, private val board: GridLayout) {
fun newBoard(size: Int) {
val squares = size * size
val people = getRandomPeople(squares)
createBoard(context, board, size, people)
}
fun createBoard(context: Context, board: GridLayout, size: Int, people: List<String>) {
destroyBoard()
board.columnCount = size
board.rowCount = size
var iterator = 0
for(col in 1..size) {
for (row in 1..size) {
cell = RelativeLayout(context)
val cellSpec = { GridLayout.spec(GridLayout.UNDEFINED, GridLayout.FILL, 1f) }
val params = GridLayout.LayoutParams(cellSpec(), cellSpec())
params.width = 0
cell.layoutParams = params
cell.setBackgroundResource(R.drawable.bordered_rectangle)
cell.gravity = Gravity.CENTER
cell.setPadding(5, 0, 5, 0)
text = TextView(context)
text.text = people[iterator++]
words.add(text.text as String)
text.maxLines = 5
text.setSingleLine(false)
text.gravity = Gravity.CENTER
text.setTextColor(0xFF000000.toInt())
cell.addView(text)
board.addView(cell)
cells.add(GameCell(cell, text, false, row, col) { })
}
}
}
private fun getRandomPeople(num: Int): List<String> {
val mFirestore: FirebaseFirestore=FirebaseFirestore.getInstance()
val mAuth: FirebaseAuth=FirebaseAuth.getInstance()
val currentUser: FirebaseUser=mAuth.currentUser!!
var validIndexes :MutableList<Int>
var chosenIndexes = mutableListOf<Int>()
var randomPeople = mutableListOf<String>()
mFirestore.collection("Names").document(gName).get().addOnSuccessListener(OnSuccessListener<DocumentSnapshot>(){ queryDocumentSnapshot->
var categorySelected:String=""
if (queryDocumentSnapshot.exists()) {
categorySelected= queryDocumentSnapshot.getString("selectedCategory")!!
print("categoryselected is:$categorySelected")
Toast.makeText(context, "Got sel category from gameroom:$categorySelected", Toast.LENGTH_LONG).show()
when(categorySelected){
"CardWords"->{
for (i in 1..num) {
validIndexes=(0..CardWords.squares.lastIndex).toMutableList()
val validIndexIndex = (0..validIndexes.lastIndex).random()
val peopleIndex = validIndexes[validIndexIndex]
chosenIndexes.add(peopleIndex)
val person = CardWords.squares[peopleIndex]
randomPeople.add(person)
validIndexes.remove(peopleIndex)
peopleIndexes = chosenIndexes.toList()
}
}
else->{}
}
}
else {
Toast.makeText(context, "Sel category does not exist", Toast.LENGTH_LONG).show()
}
}).addOnFailureListener(OnFailureListener { e->
val error=e.message
Toast.makeText(context,"Error:"+error, Toast.LENGTH_LONG).show()
})
return randomPeople.toList()
}
}
Activity A:
Board(this, gridLay!!)

How to pick every time new or unique random item from a array list in android?

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.