Develop Reference

How Can I create Interface for ItemClickListener in Kotlin?

I am new to Android & Kotlin. I want to click my row and intent it to other activity. That's why I tried to create an interface in my Adapter but it does not work. How can I create it?
My adapter code:
class NoteAdapter(private val titleTextArray: ArrayList<String>, private val imageArray: ArrayList<String>) : RecyclerView.Adapter<NoteAdapter.NoteHolder>() {
class NoteHolder (view: View) : RecyclerView.ViewHolder(view) {
var recyclerTitleText: TextView ?= null
var recyclerImageView: ImageView ?= null
init {
recyclerTitleText = view.findViewById(R.id.recyclerTitleText)
recyclerImageView = view.findViewById(R.id.recyclerImage)
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): NoteHolder {
val inflater = LayoutInflater.from(parent.context)
val view = inflater.inflate(R.layout.recycler_row, parent, false)
return NoteHolder(view)
}
override fun onBindViewHolder(holder: NoteHolder, position: Int) {
holder.recyclerTitleText?.text = titleTextArray[position]
Picasso.get().load(imageArray[position]).into(holder.recyclerImageView)
}
override fun getItemCount(): Int {
return titleTextArray.size
}
}

With Kotlin, you could to use a lambda (higher order function) to fetch the user clicks in the holder. For example, a base approach could be the next:
class YourAdapter(
private val listener: (String) -> Unit
) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
private val yourDataList = emptyList<String>()
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.compound_checkbox_terms_layout, parent, false)
return YourViewHolder(view)
}
override fun getItemCount(): Int {
TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
}
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
}
private inner class YourViewHolder(view: View) : RecyclerView.ViewHolder(view) {
init {
if (adapterPosition != RecyclerView.NO_POSITION) {
val selectedData = yourDataList[adapterPosition]
listener.invoke(selectedData)
}
}
}
}

Pass the activity context to the adapter from Activity so it can launch intent
Activity Code :
mAdapter = new CustomAdapter(this, imageArray, ArrayList);
Adapter Code :
class NoteAdapter(private val titleTextArray: ArrayList, private val imageArray: ArrayList, private val context : Context) : RecyclerView.Adapter<NoteAdapter.NoteHolder>() {
class NoteHolder (view: View) : RecyclerView.ViewHolder(view) {
var recyclerTitleText: TextView?= null
var recyclerImageView : ImageView?= null
init {
recyclerTitleText = view.findViewById(R.id.recyclerTitleText)
recyclerImageView = view.findViewById(R.id.recyclerImage)
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): NoteHolder {
val inflater = LayoutInflater.from(parent.context)
val view = inflater.inflate(R.layout.recycler_row, parent, false)
return NoteHolder(view)
}
override fun onBindViewHolder(holder: NoteHolder, position: Int) {
holder.recyclerTitleText?.text = titleTextArray[position]
Picasso.get().load(imageArray[position]).into(holder.recyclerImageView)
holder.recyclerImageView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(context, NesneTani.class);
context.startActivity(intent);
}
});
}
override fun getItemCount(): Int {
return titleTextArray.size
}
}

Create an Interface to catch the click event. (position is optional)
interface OnItemClickListener {
fun onItemClick(position: Int)
}
add OnItemClickListener as a parameter in your Adapter class
class NoteAdapter(
private val titleTextArray: ArrayList<String>,
private val imageArray: ArrayList<String>,
private val listener: OnItemClickListener
) : RecyclerView.Adapter<NoteAdapter.NoteHolder>()
Then do below inside onBindViewHolder
override fun onBindViewHolder(holder: NoteHolder, position: Int) {
listener.onItemClick(position)
}
now inside your activity, implement the OnItemClickListener
class ActivityName implements OnItemClickListener{}
and while initiating adapter, do this
mAdapter = new CustomAdapter(this, imageArray, ArrayList);
Then inside the overridden method do what you want
override fun onItemClick(position: Int) {
//start the activity you want.
}

How to implement onItemClick and onLongItemClick in RecycleView for Kotlin in android

I have used Kotlin for implementing click listeners
How to properly use it, currently click is not detecting, I am not able to detect click using below code.
class AdptEvents (val items: MutableList<TestModel>, val context: Context) : RecyclerView.Adapter<ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, p1: Int): ViewHolder {
return ViewHolder(LayoutInflater.from(context).inflate(R.layout.row_event, parent, false))
}
override fun getItemCount(): Int {
return items.size
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder?.tvAnimalType?.text = items.get(position).getName()
holder?.rootView.setOnClickListener{
clickEventRow(items,position)
true
}
holder?.rootView.setOnLongClickListener {
clickEventRow(items,position)
true
}
}
private fun clickEventRow( items: MutableList<TestModel>, position: Int ) {
Toast.makeText(context,items[position].getName(),Toast.LENGTH_LONG).show()
}
}
class ViewHolder (view: View) : RecyclerView.ViewHolder(view) {
// Holds the TextView that will add each animal to
val tvAnimalType = view.txtTitle!!
val rootView = view.eventListRootId!!
}

You dont need anything else
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder?.tvAnimalType?.text = items.get(position).getName()
holder?.rootView.setOnClickListener{
// code here
}
holder?.rootView.setOnLongClickListener {
//code here
}
}

Change your view holder. Also, if you need to get index, use adapterPosition variable.
inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
// Holds the TextView that will add each animal to
val tvAnimalType = itemView.txtTitle!!
val rootView = itemView.eventListRootId!!
init {
itemView.setOnClickListener {
Toast.makeText(context, "OnClick", Toast.LENGTH_LONG).show()
}
// OnLongClick and etc.
}
}

If you need to handle root view click events apply it dirrectly
class ViewHolder (view: View) : RecyclerView.ViewHolder(view) {
// Holds the TextView that will add each animal to
val tvAnimalType = view.txtTitle!!
view.setOnClickListener {
Toast.makeText(view.context, "OnClick", Toast.LENGTH_LONG).show()
}
view.setOnLongClickListener {
Toast.makeText(view.context, "OnLongClick", Toast.LENGTH_LONG).show()
true
}
}

OnClickListener Button inside the Adapter Class Crashing the App in Kotlin

I am trying to store the values from retrofit into a database by pressing a AddtoCartButton but app is getting crashed when I press this button. I am able to retrieve the result from retrofit without any issues but onclicklistener is the issue.
Code:
inner class MoviesAdapter : RecyclerView.Adapter<MoviesAdapter.MovieViewHolder>() {
private val movies: MutableList<Movie> = mutableListOf()
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MovieViewHolder {
return MovieViewHolder(layoutInflater.inflate(R.layout.item_movie_layout, parent, false))
}
override fun getItemCount(): Int {
return movies.size
}
override fun onBindViewHolder(holder: MovieViewHolder, position: Int) {
holder.bindModel(movies[position])
}
fun setMovies(data: List<Movie>) {
movies.addAll(data)
notifyDataSetChanged()
}
inner class MovieViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
val movieGenreTxt : TextView = itemView.findViewById(R.id.movieGenre)
val movieYearTxt : TextView = itemView.findViewById(R.id.movieYear)
val movieAvatarImage : ImageView = itemView.findViewById(R.id.movieAvatar)
val movieDescription: TextView =itemView.findViewById(R.id.movieDescription)
fun bindModel(movie: Movie) {
// movieTitleTxt.text = movie.name
movieGenreTxt.text = movie.menu
movieYearTxt.text = movie.price
Picasso.get().load(movie.picture).into(movieAvatarImage)
movieDescription.text=movie.description
var movieName:String= movie.name!!
var testvar=movie.name.toString()
}
}
}
fun addtocart(view: View)
{
Toast.makeText(context,"Success on Click", Toast.LENGTH_SHORT).show()
print testvar
}
Error:
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

Below code solves the purpose.
Code:
inner class MoviesAdapter : RecyclerView.Adapter<MoviesAdapter.MovieViewHolder>() {
private val movies: MutableList<Movie> = mutableListOf()
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MovieViewHolder {
return MovieViewHolder(layoutInflater.inflate(R.layout.item_movie_layout, parent, false))
}
override fun getItemCount(): Int {
return movies.size
}
override fun onBindViewHolder(holder: MovieViewHolder, position: Int) {
holder.bindModel(movies[position])
}
fun setMovies(data: List<Movie>) {
movies.addAll(data)
notifyDataSetChanged()
}
inner class MovieViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
val movieGenreTxt : TextView = itemView.findViewById(R.id.movieGenre)
val movieYearTxt : TextView = itemView.findViewById(R.id.movieYear)
val movieAvatarImage : ImageView = itemView.findViewById(R.id.movieAvatar)
val movieDescription: TextView =itemView.findViewById(R.id.movieDescription)
fun bindModel(movie: Movie) {
// movieTitleTxt.text = movie.name
movieGenreTxt.text = movie.menu
movieYearTxt.text = movie.price
Picasso.get().load(movie.picture).into(movieAvatarImage)
movieDescription.text=movie.description
var movieName:String= movie.name!!
var testvar=movie.name.toString()
val addtocart = itemView.findViewById<Button>(R.id.idCart)
addtocart!!.setOnClickListener {
print $testvar
Toast.makeText(context,"Success on Click", Toast.LENGTH_SHORT).show()
startActivity(intent) }
}
}
}

How to Retrieve a variable from a Inner Class to a function in Kotlin

I am trying to retrieve a testvar value from inner class Adapter to addtocart function but I am not getting the value. I am able to retrieve value inside Adapter class but not outside the class.
Code:
inner class MoviesAdapter : RecyclerView.Adapter<MoviesAdapter.MovieViewHolder>() {
private val movies: MutableList<Movie> = mutableListOf()
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MovieViewHolder {
return MovieViewHolder(layoutInflater.inflate(R.layout.item_movie_layout, parent, false))
}
override fun getItemCount(): Int {
return movies.size
}
override fun onBindViewHolder(holder: MovieViewHolder, position: Int) {
holder.bindModel(movies[position])
}
fun setMovies(data: List<Movie>) {
movies.addAll(data)
notifyDataSetChanged()
}
inner class MovieViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
val movieGenreTxt : TextView = itemView.findViewById(R.id.movieGenre)
val movieYearTxt : TextView = itemView.findViewById(R.id.movieYear)
val movieAvatarImage : ImageView = itemView.findViewById(R.id.movieAvatar)
val movieDescription: TextView =itemView.findViewById(R.id.movieDescription)
fun bindModel(movie: Movie) {
// movieTitleTxt.text = movie.name
movieGenreTxt.text = movie.menu
movieYearTxt.text = movie.price
Picasso.get().load(movie.picture).into(movieAvatarImage)
movieDescription.text=movie.description
var movieName:String= movie.name!!
var testvar=movie.name.toString()
}
}
}
fun addtocart(view: View)
{
Toast.makeText(context,"Success on Click", Toast.LENGTH_SHORT).show()
print testvar
}

Think you are looking to put a button in the RecyclerView.
In that case setOnclicklistener within the
inner class MovieViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
val addtocart = itemView.findViewById<Button>(R.id.viewprofile)
addtocart!!.setOnClickListener {
}}

Hide and show item when the user click on it using adapter

My list is about questions and answer.
I've designed an item that has the question and answer and I'm planing to hide and show the answer, not the whole item (GONE/VISIBLE), when the user click on the question. So it will be more like expandable way.
Now this is my adapter:
class FaqExpandableAdapter internal constructor(private val context: Context, private var items: List<Faq>,private val callBack: AdapterCallBack?) : RecyclerView.Adapter<FaqExpandableAdapter.MyViewHolder>() {
private val inflater: LayoutInflater = LayoutInflater.from(context)
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
val view = inflater.inflate(R.layout.item_question_faq, parent, false)
return MyViewHolder(view)
}
override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
holder.txtQuestionFaq.text = items[position].question?.toString() ?: "-"
holder.txtAnswerFaq.text = items[position].answer?.toString() ?: "-"
}
override fun getItemCount(): Int {
return items.size
}
fun update(items: List<Faq>) {
this.items = items
notifyDataSetChanged()
}
inner class MyViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
#BindView(R.id.txtQuestionFaq)
lateinit var txtQuestionFaq: AppCompatTextView
#BindView(R.id.txtAnswerFaq)
lateinit var txtAnswerFaq: AppCompatTextView
init {
ButterKnife.bind(this, itemView)
}
#OnClick(R.id.relativeRowFaq)
fun onItemClicked() {
callBack?.onItemClicked(adapterPosition)
}
}
interface AdapterCallBack {
fun onItemClicked(position: Int)
}
}
My last step is where to do the visibility action?

Kotlin : Write onClick method on your onBindViewHolder function.
holder.txtQuestionFaq.setOnClickListener {
holder.txtAnswerFaq.visibility = View.VISIBLE;
}

In onBindViewHolder() method, add below lines: (I use Java)
holder.txtQuestionFaq.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
holder.txtAnswerFaq.setVisibility(View.VISIBLE);
}
});