How to use Data Binding Android Library in Kotlin

apply plugin: 'kotlin-kapt'

android {
    dataBinding {
        enabled true
    }
}
dependencies {
    implementation 'com.android.support:recyclerview-v7:27.1.1'
    implementation 'com.android.support:cardview-v7:27.1.1'
}

 

Create a POJO class

package com.example.databindingdemo.models

data class Player(val name:String, val club: String, val country: String)

 

Convert your layout in DataBinding layout

To enable DataBinding in a layout, the root element must start with the <Layout> tag. With this, the <data> and <variable> tags are used.

<?xml version="1.0" encoding="utf-8"?>
<layout 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">

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/recycler_main"
            android:layout_width="0dp"
            android:layout_height="0dp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            android:paddingTop="15dp"/>

    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

Binding layout with data

1. A <data> tag follows <Layout>. All binding variables and methods must go inside the <data> tag.
2. Inside the <data> tag, a variable will be declared using the <variable> tag. The variable tag takes two attributes `name` and `type`. The name attribute will be the alias name and type must be of object model class. In our case, the path of the user class.
3. To bind a value, the @ annotation must be used. In the layout below, the player name, player club and player country are bound to the TextView using @ {Player.name}, @ {Player.club} and @ {Player.country}

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>
    <variable
        name="Player"
        type="com.example.databindingdemo.models.Player" />
    </data>

        <androidx.cardview.widget.CardView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_margin="15dp"
            app:cardCornerRadius="10dp">

            <androidx.constraintlayout.widget.ConstraintLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:padding="15dp">

                <TextView
                    android:id="@+id/txt_player_name"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="@{Player.name}"
                    app:layout_constraintTop_toTopOf="parent"
                    app:layout_constraintStart_toStartOf="parent"
                    android:textSize="25sp"
                    android:textStyle="bold"/>

                <TextView
                    android:id="@+id/txt_player_info"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="@{Player.club + ` | ` + Player.country}"
                    app:layout_constraintTop_toBottomOf="@+id/txt_player_name"
                    app:layout_constraintStart_toStartOf="parent"
                    android:textSize="20sp"/>

            </androidx.constraintlayout.widget.ConstraintLayout>

        </androidx.cardview.widget.CardView>

</layout>

 

Make changes in adapter

package com.example.databindingdemo.adapters

import android.content.Context
import android.view.LayoutInflater
import android.view.ViewGroup
import androidx.databinding.DataBindingUtil
import androidx.recyclerview.widget.RecyclerView
import com.example.databindingdemo.R
import com.example.databindingdemo.databinding.PlayerRowBinding
import com.example.databindingdemo.models.Player

class PlayerAdapter(private val context: Context, private val list: MutableList<Player>?) : RecyclerView.Adapter<PlayerAdapter.MyViewHolder>() {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
        val inflater = LayoutInflater.from(context)
        val binding: PlayerRowBinding = DataBindingUtil.inflate(inflater, R.layout.player_row,parent,false)
        return MyViewHolder(binding)
    }

    override fun getItemCount(): Int {
        if(list == null){
            return 0
        }
        return list.size
    }

    override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
        holder.itemBinding.player = list?.get(position)
    }

    class MyViewHolder(val itemBinding: PlayerRowBinding) : RecyclerView.ViewHolder(itemBinding.root){

        private var binding : PlayerRowBinding? = null

        init {
            this.binding = itemBinding
        }

    }

}

Make changes in Activity

package com.example.databindingdemo.activities

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.databinding.DataBindingUtil
import androidx.recyclerview.widget.LinearLayoutManager
import com.example.databindingdemo.R
import com.example.databindingdemo.adapters.PlayerAdapter
import com.example.databindingdemo.databinding.ActivityMainBinding
import com.example.databindingdemo.models.Player

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val binding: ActivityMainBinding = DataBindingUtil.setContentView(this@MainActivity, R.layout.activity_main)
        binding.recyclerMain.layoutManager = LinearLayoutManager(this@MainActivity)

        val playersList = mutableListOf<Player>()
        playersList.add(Player("Cristiano Ronaldo","Juventus","Portugal"))
        playersList.add(Player("Thiago Silva","PSG","Brazil"))
        playersList.add(Player("Sergio Ramos","Real Madrid","Spain"))

        val adapter = PlayerAdapter(this,
            playersList
        )
        binding.recyclerMain.adapter = adapter

    }
}