Develop Reference

Toggle background for a button programmitacly in android kotlin

class Split_recycler_adapter (var arrayList: ArrayList<Split_recycler_model>) :
RecyclerView.Adapter<Split_recycler_adapter.Viewholder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): Viewholder {
val v = LayoutInflater.from(parent.context).inflate(R.layout.changesplit_recycler_item,parent,false)
return Viewholder(v)
}
override fun onBindViewHolder(holder: Viewholder, position: Int) {
val split_modal = arrayList[position]
var checked = true
Log.e("position_outside_loop->","$position")
holder.split_text.text = split_modal.getText()
holder.split_text.setOnClickListener{
if(checked){
Log.e("check->","Working")
holder.split_text.setBackgroundResource(R.drawable.green_button_gradient)
holder.split_text.setTextColor(Color.parseColor("#454546"))
checked = false
}else{
holder.split_text.setBackgroundResource(R.drawable.dropdown_gradient)
holder.split_text.setTextColor(Color.parseColor("#A4A4A4"))
checked = true
}
}
}
override fun getItemCount(): Int {
return arrayList.size
}
class Viewholder(Itemview: View) : RecyclerView.ViewHolder(Itemview) {
val split_text : TextView = Itemview.findViewById(R.id.split_text)
}
}
This code helps me to change the background of the button when clicked and revert the background when one more click is done but this is not the exact thing i want , I need to toggle the background on click, when one click is done it should want to remove the background of the other button , only one button should be highlighted at a time , Please help me if any one know the solution

You can't do it this way.
You have added a click listener in a binder and performed checked logic for that item mainly situated at that holder position. It won't affect other items at other positions. So to update other positions' state, you have to manage the state for each item by adding isChecked variable in Split_recycler_model class.
class Split_recycler_model {
var isChecked : Boolean = false
}
And in onClick of view, update your list item for that particular adapterPosition.
Updated click action,
holder.split_text.setOnClickListener{
checkItem(adapterPosition)
}
fun checkItem(adapterPosition:Int) {
arrayList.forEachIndexed{index,item ->
item.apply{
isChecked = (index == adapterPosition)
}
}
/**
Here you can manually calculate the changes
to update adapter to improve performance.
For now, I'm updating it with the `notifyDataSetChanged` method.
*/
notifyDataSetChanged()
}

Android - RecyclerView - edittext notifyItemChanged keep focus and continue typing

I have a RecyclerView which has an EditText in its items.
For each EditText I have added a textChangeListener.
Whenever the user types a character I want to do an input validation and so I can change the item, for example show red border in case of wrong input etc...
After I do the validation I call:
adapter.notifyItemChanged(itemPosition)
to update the view.
But the problem is that the focus is lost from the EditText and I have to click again inside the box in order to continue typing.
Is there a solution for this case? How can I continue typing while the view is updated after calling notifyItemChanged ?
ADAPTER
class ItemAdapter() : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
val inflater = LayoutInflater.from(parent.context)
val binding = LayoutItemBinding.inflate(inflater, parent, false)
binding.editText.addTextChangedListener {
// Do layout changes....
if (isInvalidInput) {
item.setError = true
....
...
}
adapter.notifyItemChanged(itemPosition)
}
return ItemViewHolder(binding)
}
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
holder.bind(items[position])
}
inner class ItemViewHolder(val binding: LayoutItemBinding)
: RecyclerView.ViewHolder(binding.root) {
fun bind(model: ItemModel) {
// Setup view for item
}
}
}

Try to move your error setting code in the bind function of the ViewHolder and update the error status outside of the TextWatcher:
class ItemAdapter() : RecyclerView.Adapter<RecyclerView.ViewHolder>()
{
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
val inflater = LayoutInflater.from(parent.context)
val binding = LayoutItemBinding.inflate(inflater, parent, false)
return ItemViewHolder(binding)
}
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
holder.bind(items[position], position)
}
inner class ItemViewHolder(val binding: LayoutItemBinding) : RecyclerView.ViewHolder(binding.root) {
fun bind(model: ItemModel, position: Int) {
binding.editText.addTextChangedListener {
// Update the ItemModel on text change
adapter.notifyItemChanged(position)
}
// Update the view error status everytime it is updated
val isInvalidInput = ... // Add your logic
if (isInvalidInput) {
model.setError = true
....
....
}
}
}
}

First, Please post your code.
If you called notifyDatasetChanged(), all views of recyclerview will refreshed (it means that the views could be recreated.).
So if you want remain focus in edittext, you not call notifyDatasetChanged() or set focus to your edittext after notifyDataChanged().
But setFocus is bit more difficult.
So I suggest method that update views of recyclerview without call notifyDatasetChanged().
I think you can directly update view of recyclerview without call notifyDataChanged().

You should save the id of item that contains the EditText that is editing. And in the bind() method of ViewHolder, you will check if the item is currently being edit, you will call requestFocus() method on EditText.
And please take note that when you call notifyDataChanged(), the RecycleView maybe check the data of each item to know whether it was changed or not. If the data of an item was changed, RecycleView will redraw that item.

notifyDataSetChanged() not updating UI

I want to display new list of items retrieved from ViewModel in custom RecyclerView.Adapter. To do so I pass the retrieved list to adapter and invoke notifyDataSetChanged(), but nothing changes on the UI.
I've debugged code and adapter's list had 1 element (UI displayed 1 element), new retrieved list had 2 elements - after setting new list in adapter and invoking notifyDataSetChanged() UI didn't change, but should append that 1 element.
Fragment's code:
trip_details_participantsList.layoutManager = LinearLayoutManager(activity, LinearLayoutManager.HORIZONTAL, false)
trip_details_participantsList.adapter = userBriefAdapter
tripsDetailsViewModel.getTripParticipants(tripId).observe(this, Observer {participants ->
tripsDetailsViewModel.getUsersBriefs(participants.map { x -> x.userId }).observe(this, Observer{ users ->
userBriefAdapter.setData(users)
})
})
Custom Adapter and ViewHolder:
class UserBriefAdapter : RecyclerView.Adapter<UserBriefViewHolder>() {
private var users: List<UserBrief> = mutableListOf()
fun setData(items: List<UserBrief>){
this.users = items
notifyDataSetChanged()
}
override fun onBindViewHolder(holder: UserBriefViewHolder, position: Int) =
holder.bind(users[position])
override fun getItemCount() = users.size
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): UserBriefViewHolder {
val inflater = LayoutInflater.from(parent.context)
return UserBriefViewHolder(inflater, parent)
}
}
class UserBriefViewHolder(inflater: LayoutInflater, parent: ViewGroup) : RecyclerView.ViewHolder(inflater.inflate(
R.layout.trip_details_list_item, parent, false)) {
private var profilePictureImageView: ImageView = itemView.findViewById(R.id.trips_details_profile_image)
fun bind(userBrief: UserBrief){
Picasso.get()
.load(userBrief.profilePictureUrl)
.into(profilePictureImageView)
}
}
I've read existing topics about it, but every accepted solution is something like my adapter's setData() function with notifyDataSetChanged(). I've also tried to set new instance of UserBriefAdapter to RecyclerView each time observed values changed, but results were the same. When I go back and forth the view, then it correctly displays the elements, but I want to achieve this without changing the view.

It could be an issue of threading. Try to post a runnable to the main thread in your observer callback:
tripsDetailsViewModel.getUsersBriefs(participants.map { x -> x.userId }).observe(this, Observer{ users ->
view?.post { userBriefAdapter.setData(users) }
})

Done some more debugging and figured out that notifyDataSetChanged() wasn't the problem. I was passing wrong profilePictureUrl to UserBriefViewHolder, so Picasso library doesn't fetch an image and in consequence UI wasn't updated.

The notifyItemRangeInserted command isn't working

I'm having a problem when call the notifyItemRangeInserted of the adapter. When I call this method, nothing happens, simple as that. I've tried to set some println() in the ViewHolderAdapter, but he isn't called, so I can't view the prints.
I've tried all of the "notify" commands of the adapter, and none of these work. Simply nothing happens.
That's my MainActivity. All the objects and arrays I've tested, all of them are working like a charm. I can't understand why the notify doesn't work.
class MainActivity:AppCompatActivity(){
//Declarations of the variables
var pageNumber = 1
var limitPerPage = 5
lateinit var product: Product
var productList = ArrayList<EachProduct>()
var myAdapter =ViewHolderAdapter(productList, productList.size)
override fun onCreate(savedInstanceState:Bundle?){
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
recyclerView.layoutManager = LinearLayoutManager(this#MainActivity)
recyclerView.adapter = myAdapter
The code to add items on the list and notify the ViewHolderAdapter is
//update the product list
fun updateProductList(product:Product){
for(i in 0 until 5 step 1){
productList.add(product.produtos[i])
}
showData(productList,pageNumber*limitPerPage)//then notify
}
fun showData(productList:List<EachProduct>,productsListSize:Int){
myAdapter.notifyItemRangeInserted(0,productList.size)
}
That's my ViewHolderAdapter class
class ViewHolderAdapter(private var products: List<EachProduct>, private val productsListSize: Int): RecyclerView.Adapter<ViewHolderAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent:ViewGroup,viewType:Int): ViewHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.recyclerview_layout, parent, false)
returnViewHolder(view)
}
override fun getItemCount() = productsListSize
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.productName.text=products[position].nome
Picasso.get().load(products[position].fabricante.img).into((holder.productLogo))
}
class ViewHolder(itemView: View): RecyclerView.ViewHolder(itemView) {
val productName:TextView=itemView.ProductName
var productLogo:ImageView=itemView.ProductLogo
}
}
I expect the ViewHolderAdapter to be called, but this is not occurring. Why is that happens? I can't understand. I'll be very grateful if someone could help me.

Because initial value of the variable productsListSize is zero. Remove it from the constructor and change adapter like this:
class ViewHolderAdapter(private var products: List<EachProduct>): RecyclerView.Adapter<ViewHolderAdapter.ViewHolder>() {
override fun getItemCount() = products.size
}

A reason can be that the initial size of the item list you want to show is 0 and the recycler view height is set to wrap content. At the moment, for this case I see 2 options:
Keep wrap content for recycler view and make sure the initial list size > 0.
Set the height of the recycler view to match_parent or a fixed size and notifyItemRangeInserted will work without issues.

Cannot access var object of inner class in kotlin

I am trying to write a RecyclerView adapter class in Kotlin for android. I am trying to use the traditional way of creating a custom viewer class, for custom objects, and use a click listener in that. While I am able to do rest of the things like access the variables of inner class and show the RecyclerView, what I have not been able to do is add click listener to the var objects of inner class.
ie something like
var convertView : View? = itemView
convertView.setOnClickListener(this)
Following is my complete code of adapter class
public open class TestAdapter(val items: MutableList<Any>, val context: Activity) : RecyclerView.Adapter<TestAdapter.CustomViewHolder>() {
public var mItem: MutableList<Any> = items
public var mActivity: Activity = context
protected var clickListener: ExampleInterface? = null
public interface ExampleInterface {
fun click(pos: Int) {
}
}
open public fun setListener(mInterFaceListener: ExampleInterface) {
clickListener = mInterFaceListener
}
override fun onCreateViewHolder(p0: ViewGroup, p1: Int): CustomViewHolder {
var parentLayout: View = LayoutInflater.from(mActivity).inflate(R.layout.custom_view, p0, false)
return CustomViewHolder(parentLayout)
// return CustomViewHolder(LayoutInflater.from(mActivity).inflate(R.layout.custom_view, p0, false))
}
override fun getItemCount(): Int {
return mItem.size
TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
}
override fun onBindViewHolder(p0: CustomViewHolder, p1: Int) {
p0.dataView.text = mItem.get(p1).toString()
}
inner class CustomViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView), View.OnClickListener {
var convertView: View? = itemView
var dataView: TextView = convertView!!.findViewById(R.id.data)
var mposition = adapterPosition
override fun onClick(p0: View?) {
if (clickListener != null) {
clickListener!!.click(mposition)
}
TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
}
}
}
So if you see these two lines in CustomView class
var convertView: View? = itemView
var dataView: TextView = convertView!!.findViewById(R.id.data)
I cannot access these variables "convertView" and "dataView" so that I can set clicklistener to them. So how to achieve it ?
Thanks :)

I referred to this site
https://www.raywenderlich.com/367-android-recyclerview-tutorial-with-kotlin
Here I go to know my mistake , I need to use init in the class, there I am able to access it and initialize on click listener. Got it working
init {
convertView?.setOnClickListener(this)
}
Though the above answer could be acceptable as well, as I am new to Kotlin I cannot say which one is the better option, but my requirement is satisfied with the above mentioned site.
Thank you :)

In RecyclerView adapters, You could place the OnClickListeners in onCreateViewHolder in order to prevent them from being set each time onBindViewHolder is called (as onBindViewHolder is called multiple times when RecyclerView is scrolled). Use parentLayout in your onCreateViewHolder to access your views and set onClickListener to them. to determine current position in onCreateViewHolder you can do as below :
override fun onCreateViewHolder(p0: ViewGroup, p1: Int): CustomViewHolder {
val parentLayout: View = LayoutInflater.from(mActivity).inflate(R.layout.custom_view, p0, false)
val customViewHolder = CustomViewHolder(parentLayout)
parentLayout.myExampleTextView.setOnClickListener {
// Place onClick logic here.
// If you need position, do as bellow :
val adapterPosition = customViewHolder.adapterPosition
if(adapterPosition != RecyclerView.NO_POSITION) {
// Place your position dependent logic here
}
}
return customViewHolder
}
UPDATE:
I updated the code snippet above and added the RecyclerView.NO_POSITION (which is equal to -1) check. The reason for the position being returned as -1 is explained below.
From android docs:
The other set of position related methods are in the form of
AdapterPosition. (e.g. getAdapterPosition(), findViewHolderForAdapterPosition(int)) You should use these methods
when you need to work with up-to-date adapter positions even if they
may not have been reflected to layout yet. For example, if you want to
access the item in the adapter on a ViewHolder click, you should use
getAdapterPosition(). Beware that these methods may not be able to
calculate adapter positions if notifyDataSetChanged() has been called
and new layout has not yet been calculated. For this reasons, you
should carefully handle NO_POSITION or null results from these
methods.

you can access them in the onBindViewHolder using the p0 this way p0.dataView so there you can set listeners successfully