Develop Reference

Recycler view pagination in kotlin android development

Want to show images from internal storage in android studio using recycler view, did that but now want to use pagination, can it be done using pagination?
class TestingAdapter(var URI_String: ArrayList<String>, var activity: Activity) :
RecyclerView.Adapter<TestingAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view: View = LayoutInflater.from(parent.context).inflate(R.layout.view, parent, false)
return ViewHolder(view)
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
Glide.with(activity).load(URI_String[position]).into(holder.imageView)
}
override fun getItemCount(): Int {
return URI_String.size
}
class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
var imageView: ImageView
init {
imageView = itemView.findViewById(R.id.imageView2)
}
}
}

android - Creating and using ViewBinder inside a RecyclerView adapter

In my app, there is an Activity which has a RecyclerView inside, which loads the list of options needed for that screen.
In the code below, i tried to implement a binder, which is needed because of the recent Android changes.
However, when i open the activity starts, the application crashes, throwing this error, linking the line with binding = ItemSettingsBinding.bind(binding.root):
kotlin.UninitializedPropertyAccessException: lateinit property binding has not been initialized
What am i doing wrong? What's the correct way to implement a binder inside an adapter?
AdapterSettings.kt
class AdapterSettings(
var settingsList: List<DataItemSettings>,
var listener: OnItemClickListener
) : RecyclerView.Adapter<AdapterSettings.SettingsViewHolder>() {
private lateinit var binding: ItemSettingsBinding
inner class SettingsViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView), View.OnClickListener {
init {
itemView.setOnClickListener(this)
}
override fun onClick(p0: View?) {
val position : Int = adapterPosition
if (position != RecyclerView.NO_POSITION) {
listener.OnItemClick(position)
}
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): SettingsViewHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.item_settings, parent, false)
return SettingsViewHolder(view)
}
override fun getItemCount(): Int {
return settingsList.size
}
override fun onBindViewHolder(holder: SettingsViewHolder, position: Int) {
binding = ItemSettingsBinding.bind(binding.root)
holder.itemView.apply {
binding.rvTitle.text = settingsList[position].stringTitle
binding.rvDescription.text = settingsList[position].stringDescription
binding.rvIcon.setImageResource(settingsList[position].itemIcon)
}
}
interface OnItemClickListener {
fun OnItemClick(position: Int)
}
}

I believe you're missing your inflate in onCreateViewHolder:
// Pseudo-Code
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): SettingsViewHolder {
val binding = ItemSettingsBinding
.inflate(LayoutInflater.from(parent.context), parent, false)
return SettingsViewHolder(binding)
}
Then you can make use of it.

Create the binding in onCreateViewHolder and pass the binding into the ViewHolder instead of the inflated View. Thus you create a binding for each created view and only need to do the apply stuff in the onBindViewHolder
Example:
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): SettingsViewHolder {
val view = LayoutInflater.from(parent.context).inflate(R.layout.item_settings, parent, false)
val binding = ItemSettingsBinding.bind(view)
return SettingsViewHolder(binding)
}
override fun onBindViewHolder(holder: SettingsViewHolder, position: Int) {
holder.binding.apply {
rvTitle.text = settingsList[position].stringTitle
rvDescription.text = settingsList[position].stringDescription
rvIcon.setImageResource(settingsList[position].itemIcon)
}
}
Adapt your ViewHolder accordingly

There is indeed another way to ViewBind in an adapter.
First, we need to setup the ViewHolder in a different way:
inner class SettingsViewHolder(private val binding: ItemSettingsBinding):
RecyclerView.ViewHolder(binding.root), View.OnClickListener {
With this, we created a binding value inside the brackets, so we are able to call the items of the actual view or layout trough binding.root
Inside the viewholder, we need to create a function used to bind our items. We can either bind like this:
fun bind(item: Item) {
binding.item = item
binding.executePendingBindings()
}
Or like this:
fun bind(item: DataItemSettings) {
binding.rvTitle.text = settingsList[position].stringTitle
binding.rvDescription.text = settingsList[position].stringDescription
binding.rvIcon.setImageResource(settingsList[position].itemIcon)
}
NOTICE: 'getter for position: Int' is deprecated. Deprecated in Java.
And, final step, we need to write this, inside bindViewHolder:
override fun onBindViewHolder(holder: SettingsViewHolder, position: Int) {
holder.bind(settingsList[position])
}

OnBindViewHolder is triggered only once

What is Happening: Even though there are two elements in val list: ArrayList<StudentModel> collection as seen in image below and I have explicitly given size 2 in getItemCount(). Only once onBindViewHolder is triggered
AdapterCode
class ListAdapter(private val list: ArrayList<StudentModel>,val context: Context) : RecyclerView.Adapter<MovieViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MovieViewHolder {
return MovieViewHolder(LayoutInflater.from(context).inflate(R.layout.frag_disp_group_blocks, parent, false))
}
override fun getItemCount(): Int {
Timber.i("$list.size")
return 2
}
override fun onBindViewHolder(holder: MovieViewHolder, position: Int) {
val movie = list[position]
Timber.i("$movie")
Timber.i("$movie.get(position)")
holder?.tvAnimalType?.text = ""
}
}
class MovieViewHolder (view: View) : RecyclerView.ViewHolder(view) {
// Holds the TextView that will add each animal to
val tvAnimalType = view.list_title
}

passing a context from activity/fragment is not necessary unless they serve the purpose of their usage. Use context from the onCreateViewHolder parameter parent.
return MovieViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.frag_disp_group_blocks, parent, false))

This was a mistake from my side .... I had given the matchParent params so it was triggering once. wrapContent did solve the problem

Recycleview in Kotlin

I have a problem with:
RecyclerView: No adapter attached; skipping layout
I can't define adapter in OnCreate because the list is not ready.
How I can define adapter in OnCreate? or what is a possible solution for resolve my problem?

In onCreate I did:
adapter = MyAdapter(this#MyActivity)
adapter.data = ArrayList()
Then later I just set adapter.date = xxx
In my adapter I have:
class MyAdapter(val activity: MyActivity) :
RecyclerView.Adapter<MyAdapter.BodyViewHolder>() {
var data: MutableList<MyModel>? = null
set(value) {
field = value
notifyDataSetChanged()
}
override fun getItemCount() = data?.size ?: 0
fun ViewGroup.inflate(#LayoutRes layoutRes: Int, attachToRoot: Boolean = false): View {
return LayoutInflater.from(context).inflate(layoutRes, this, attachToRoot)
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): BodyViewHolder {
val view = LayoutInflater.from(parent.context)
.inflate(R.layout.my_layout, parent, false)
return BodyViewHolder(view)
}
override fun onBindViewHolder(holder: BodyViewHolder, position: Int) {
holder.bindValue(data?.get(position), activity)
}
class BodyViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
fun bindValue(record: MyModel?, activity: MyActivity) {
record?.let {
itemView.mTextView.text = ....
}
}
}
}
Worth mentioning that the height of my recycler view is wrap_content
<android.support.v7.widget.RecyclerView
android:id="#+id/mRecyclerView"
android:layout_width="match_parent"
android:layout_height="wrap_content" />

It's totally ok if you don't have data in onCreate. What you need to do is to define the adapter and bind it with your RecyclerView. Once you have data ready, add data to the list in adapter and notify it. Example as below
class MyAdapter: RecyclerView.Adapter<MyViewHolder>() {
private val data = mutableListOf<MyModel>()
override fun getItemCount() = data.count()
fun addData(data : MyModel) {
// add single data the list or call addAll() to add a group of data.
// just remember not to replace the variable
}
fun clearData() {
}
fun deleteData(id: Int) {
}
}

class adpCoba(val context: Context, val datalist:ArrayList<dataCoba>):RecyclerView.Adapter<adpCoba.MyViewHolder>(){
class MyViewHolder (itemView:View):RecyclerView.ViewHolder(itemView){
val text :TextView=itemView.findViewById(R.id.textcoba)
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
val itemView = LayoutInflater.from(context).inflate(R.layout.fetch_coba,parent,false)
return MyViewHolder(itemView)
}
override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
val currntItem = datalist [position]
holder.text.text= currntItem.nama
}
override fun getItemCount(): Int {
return datalist.size
}
}

RecyclerAdapter is creating multiple view back to back

I am using recyclerview to display images in cardview. When I load images from the url. It loads well from first time but when It loads for second time it is not displayed properly.
How to fix it? Here is the code
override fun getItemCount(): Int {
dataList = FlickrDBOperation.dataArray
if (dataList!!.isEmpty())
return 0
Log.e("count",dataList!!.size.toString())
return dataList!!.size
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): Holder {
var itemView: View = LayoutInflater.from(parent.context).inflate(R.layout.imagelist_row,parent,false)
var viewHolder: FlickrAdapter.Holder = FlickrAdapter.Holder(itemView)
return viewHolder
}
override fun onBindViewHolder(holder: Holder, position: Int) {
holder.image_name.text = dataList!!.get(position).name
Picasso.with(context).load(dataList!!.get(position).preUrl).into(holder.row_image)
}
class Holder(itemView: View?) : RecyclerView.ViewHolder(itemView) {
val row_image: ImageView
val image_name: TextView
init {
row_image = itemView!!.findViewById<ImageView>(R.id.row_image)
image_name = itemView!!.findViewById<TextView>(R.id.image_name)
}
}