ANDROID RECYCLER VIEW EXAMPLE WITH KOTLIN

Now as google has officially announced kotlin as official language for Android Development, today I am writing a tutorial about creating Android Recycler View with kotlin. Though Android Studio 3.0 is not released yet, but you can get the beta release for android development in kotlin. Visit the link to download android studio 3.0 beta release (get the stable build if released).
Here is the final image of our recyclerview.

                                                             

                                                                    Recycler View Using Kotlin - Android Tech Point

Steps to Create Recycler View

 You can create your recycler view by following these simple steps 

• Add the recycler view in your xml.
• Add a new layout xml file for the list item and add card view in it.
• Create your data class.
• Write your adapter class.
• Set the adapter for the recycler view.

And that's all. Now we will see the implementation in a bit details with the actual code.

Implementation for Recycler View with Kotlin

Drag  and drop the recycler view, android studio will automatically add the dependency for recycler view in the Build,gradle(app).
                                           
                                                                                   Recycler View - Android Tech Point
Here is the code for the recycler view in activity_main.xml
activity_main.xml

	<?xml version="1.0" encoding="utf-8"?>
	<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
	xmlns:app="http://schemas.android.com/apk/res-auto"
	xmlns:tools="http://schemas.android.com/tools"
	android:layout_width="match_parent"
	android:layout_height="match_parent"
	tools:context="com.example.farooq.firstappwithkotlin.MainActivity">
	<android.support.v7.widget.RecyclerView
	android:id="@+id/recyclerview"
	android:layout_width="match_parent"
	android:layout_height="match_parent" />
	</LinearLayout>

Create a new xml layout file and name it list_item.xml. Drag and drop the card view in the design section (Android Studio will automatically add the dependency for card view) create the design for a single row.
list_item.xml

	<?xml version="1.0" encoding="utf-8"?>
	<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
	xmlns:tools="http://schemas.android.com/tools"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:orientation="horizontal">
	<android.support.v7.widget.CardView
	android:layout_width="match_parent"
	android:layout_margin="4dp"
	android:layout_height="wrap_content">
	<LinearLayout
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:orientation="horizontal">
	<ImageView
	android:id="@+id/imageview"
	android:layout_width="0dp"
	android:layout_height="match_parent"
	android:layout_weight="1"
	android:scaleType="centerCrop" />
	<TextView
	android:id="@+id/textview"
	android:layout_marginLeft="4dp"
	android:layout_marginRight="4dp"
	android:layout_marginStart="4dp"
	android:layout_marginEnd="4dp"
	android:layout_width="0dp"
	android:layout_height="wrap_content"
	android:layout_weight="8"
	android:textSize="24sp"
	tools:text="This is a sample text" />
	</LinearLayout>
	</android.support.v7.widget.CardView>
	</LinearLayout>

Now we will add the data class or you can say POJO class in kotlin. It is very very simple in kotlin. You don't have to write any boilerplate code.
MyData.kt

	package com.example.farooq.firstappwithkotlin
	import android.graphics.Bitmap
	/**
	* Created by androidtechpoint.blogspot.com on 9/12/2017.
	*/
	data class MyData(var text:String, var image:Bitmap)

Next step is to create our RecyclerViewAdapter.kt. It is pretty much same as we usually do in java.
RecyclerViewAdapter.kt 

	package com.example.farooq.firstappwithkotlin
	import android.support.v7.widget.RecyclerView
	import android.util.Log
	import android.view.LayoutInflater
	import android.view.View
	import android.view.ViewGroup
	import android.widget.ImageView
	import android.widget.TextView
	/**
	* Created by farooq on 9/12/2017.
	*/
	class RecyclerViewAdapter(val list:ArrayList<MyData>):RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder>() {
	override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerViewAdapter.ViewHolder {
	val v = LayoutInflater.from(parent.context).inflate(R.layout.list_item, parent, false)
	return ViewHolder(v)
	}
	//this method is binding the data on the list
	override fun onBindViewHolder(holder: RecyclerViewAdapter.ViewHolder, position: Int) {
	holder.bindItems(list[position])
	}
	//this method is giving the size of the list
	override fun getItemCount(): Int {
	return list.size
	}
	class ViewHolder(view: View): RecyclerView.ViewHolder(view) {
	fun bindItems(data : MyData){
	val _textView:TextView = itemView.findViewById(R.id.textview)
	val _imageView:ImageView = itemView.findViewById(R.id.imageview)
	_textView.text = data.text
	_imageView.setImageBitmap(data.image)
	//set the onclick listener for the singlt list item
	itemView.setOnClickListener({
	Log.e("ItemClicked", data.text)
	})
	}
	}
	}

Its time to use our custom adapter and display the list of items on the screen. In your main activity, set the adapter for the recycler view.
MainActivity.kt

	package com.example.farooq.firstappwithkotlin
	import android.graphics.BitmapFactory
	import android.support.v7.app.AppCompatActivity
	import android.os.Bundle
	import android.support.v7.widget.LinearLayoutManager
	import android.support.v7.widget.RecyclerView
	import android.widget.LinearLayout
	class MainActivity : AppCompatActivity() {
	override fun onCreate(savedInstanceState: Bundle?) {
	super.onCreate(savedInstanceState)
	setContentView(R.layout.activity_main)
	val _recyclerView: RecyclerView = findViewById(R.id.recyclerview)
	_recyclerView.layoutManager = LinearLayoutManager(this, LinearLayout.VERTICAL, false)
	val items = ArrayList<MyData>()
	//adding some dummy data to the list
	items.add(MyData("text 1", BitmapFactory.decodeResource(resources, R.drawable.icon1)))
	items.add(MyData("text 2", BitmapFactory.decodeResource(resources, R.drawable.icon2)))
	items.add(MyData("text 3", BitmapFactory.decodeResource(resources, R.drawable.icon3)))
	items.add(MyData("text 4", BitmapFactory.decodeResource(resources, R.drawable.icon4)))
	items.add(MyData("text 5", BitmapFactory.decodeResource(resources, R.drawable.icon5)))
	items.add(MyData("text 6", BitmapFactory.decodeResource(resources, R.drawable.icon1)))
	items.add(MyData("text 7", BitmapFactory.decodeResource(resources, R.drawable.icon2)))
	items.add(MyData("text 7", BitmapFactory.decodeResource(resources, R.drawable.icon3)))
	items.add(MyData("text 8", BitmapFactory.decodeResource(resources, R.drawable.icon4)))
	items.add(MyData("text 9", BitmapFactory.decodeResource(resources, R.drawable.icon5)))
	items.add(MyData("text 10", BitmapFactory.decodeResource(resources, R.drawable.icon1)))
	items.add(MyData("text 11", BitmapFactory.decodeResource(resources, R.drawable.icon2)))
	items.add(MyData("text 12", BitmapFactory.decodeResource(resources, R.drawable.icon2)))
	items.add(MyData("text 13", BitmapFactory.decodeResource(resources, R.drawable.icon3)))
	items.add(MyData("text 14", BitmapFactory.decodeResource(resources, R.drawable.icon4)))
	items.add(MyData("text 15", BitmapFactory.decodeResource(resources, R.drawable.icon5)))
	items.add(MyData("text 16", BitmapFactory.decodeResource(resources, R.drawable.icon1)))
	//creating our adapter
	val adapter = RecyclerViewAdapter(items)
	//now adding the adapter to recyclerview
	_recyclerView.adapter = adapter
	}
	}

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