is there any alternate for arraylist.remove(element) function?

Issue

my recycler view reloads with spinner value, selected data is stored in a global arraylist, and here is my recycler view code to do the selection and deselection. Selection and deselection works just fine, but when i select and change spinner value, and then come to back original spinner value, where items are already selected, deselction happens, but item is not removed from the global arraylist. While debugging i found that cursor reaches there, but i dont know why .remove() isnt working. Is there any alternative for it or am i doing wrong? Is there anything i should know that why isnt the item removed.

. . .

class RecyclerViewAdapter(val dataList:ArrayList<ModelClass>,val onItemClicked: (Int) -> Unit):RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder>() {

 object ob {
     val dataSelected = ArrayList<ModelClass>()
     val hm = HashMap<ModelClass,String>()


 }


 fun setData(listModel: List<ModelClass>) {
     dataList.clear()
     dataList.addAll(listModel)
     notifyDataSetChanged()

 }


 override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
     val binding = ItemViewBinding.inflate(
         LayoutInflater.from(parent.context), parent, false
     )
     return ViewHolder(binding, parent.context)
 }


 @SuppressLint("ResourceAsColor")
 override fun onBindViewHolder(holder: ViewHolder, position: Int) {

     holder.bindItems(dataList[position])

 }

 override fun getItemCount() = dataList.size

 inner class ViewHolder(
     val binding: ItemViewBinding,
     val context: Context
 ) : RecyclerView.ViewHolder(binding.root) {

     var count=0
     @SuppressLint("ResourceAsColor")
     fun restore() {


         for (i in 0 until ob.dataSelected.size) {
             for (j in 0 until dataList.size) {
                 if (ob.dataSelected[i].sku_code == (dataList[j]).sku_code) {
                     if (adapterPosition == j) {

                         itemView.isSelected = true
                         itemView.setBackgroundColor(R.color.black)
                         count=count+1
                         println("****")

                     }

                 }

             }
         }

         if(!itemView.isSelected){

                 itemView.isSelected = false
                 itemView.setBackgroundResource(0)


         }
     }

     @SuppressLint("ResourceAsColor", "ResourceType")
     fun bindItems(data: ModelClass) = with(binding) {


         binding.itemQuant.text = data.item_quant
         binding.itemName.text = data.item_name
         binding.mfgName.text = data.mfg
         binding.quantity.text = data.item_stock.toString()


         count=0

         restore()
         itemView.setOnClickListener {

            count += 1
             var isPresent:Int
             if (count%2 == 0){
                 isPresent=1
             }
             else
             {
                 isPresent=0
             }


             if (isPresent == 1) {
                 it.setBackgroundResource(0)  //works
                 ob.dataSelected.remove(dataList[adapterPosition]) //doesnt work if spinner value is changed and changed back. works while still on same screen.

             } else {
                 if (isPresent == 0) {
                     it.setBackgroundColor(R.color.black)


                     ob.dataSelected.add(dataList[adapterPosition])
                     
                }
                 // onItemClicked.invoke(adapterPosition)
             }

         }

     }
 }

}

Solution

Are you sure it's not being removed? Have you set a breakpoint and checked the contents of the array (or just logged it)? Because it looks like when you're binding a viewholder, you just check if the item is in dataSelected, and if it is you set the view's selected and backgroundColor values. It doesn't look like you change them back if it's not in dataSelected, so that selected appearance "sticks".

It looks like you're trying to reset them with this:

if(!itemView.isSelected){
    itemView.isSelected = false
    itemView.setBackgroundResource(0)
}

but that only works if itemView.selected hasn't been set to true, which it has if your item is in dataSelected. You need to do it like this:

 for (i in 0 until ob.dataSelected.size) {
     for (j in 0 until dataList.size) {
         // rolling multiple conditions into a single value makes it easier to do an if/else
         val selected = ob.dataSelected[i].sku_code == (dataList[j]).sku_code && adapterPosition == j
         if (selected) {
             itemView.isSelected = true
             itemView.setBackgroundColor(R.color.black)
             count=count+1
             println("****")
         } else {
             itemView.isSelected = false
             itemView.setBackgroundResource(0)
         }

     }
 }

That way you're always updating the contents of the view holder to reflect the state of the current item. That's especially important in RecyclerViews, because the point of those is that the ViewHolders get reused to display different items, and any View attributes you don't set when binding (e.g. colours, checkbox statuses) will just stay on whatever they were last set to when displaying some other item.

---

btw, you can simplify that looping situation by just checking if anything in dataSelected has the SKU you're looking for:

val itemSku = datalist[adapterPosition].sku_code
val selected = ob.dataSelected.any { it.sku_code == itemSku }

ideally you wouldn't be using adapterPosition to find the current item either - the item you're matching is passed in to bindItems (as data), you could just pass that to your restore function

---

edit if the items aren't being removed from dataSelected, at a guess it's because the object you're fetching from dataList "doesn't exist" in dataSelected. By "doesn't exist" I mean there isn't an object that equals the one you're trying to remove.

ob.dataSelected.remove(dataList[adapterPosition])

I'm assuming that might be the case because you're not doing straight object comparisons when you're checking if an item is in the selected array, you're specifically comparing their sku_code values instead

if (ob.dataSelected[i].sku_code == (dataList[j]).sku_code)

If you can't just do if (obj.dataSelected[i] == dataList[j]), then remove won't work either - it's the same check. So maybe you need to look into making those objects equal (e.g. using data classes if that works for what you're doing), or use removeAll with a predicate (remove only works with a specific item):

ob.dataSelected.removeAll { it.sku_code == dataList[adapterPosition].sku_code }

You'll still have the problem of the UI not being updated though, like the first part of the answer explains! So you might have two problems here

Answered By - cactustictacs