2. How to Use Data Binding Library with Kotlin

2.1. DataBinding:

• Data binding offers flexibility as well as broad compatibility to your code.
• we have been using Data Binding Library to bind application logic and layouts.
• It’s a library that allows you to bind the data of your models directly to the xml views in a very flexible way.
• Kotlin very much supports Data Binding Library. We can still bind our layouts with the Kotlin class.
• If you want to use data binding and Kotlin, here are a few things to keep in mind:
• Data binding is a support library, so it can be used with all Android platform versions all the way back to Android 2.1 (API level 7+).
• To use data binding, you need Android Plugin for Gradle 1.5.0-alpha1 or higher. You can see here how to update the Android Plugin for Gradle.
• Android Studio 3.0 fully supports kotlin
• First of all, create an Android Studio project and add a dependency for Kotlin and few changes for your Project level build.gradle
• We also need to add the Data Binding dependency and the ones of Kotlin to the build.gradle file of our app.
• //Notice that I made the compiler version a variable in the project level build gradle so it can be managed from a single place. That’s all the configuration we need to start using Data Binding with Kotlin.

Now for Kotlin and Data Binding to work together, add a Kotlin Model Class. This model class is going to bind your layout with your Kotlin activity class.

2.2. activity_main:

<?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">
   <data>
       <variable
           name="nithya"
           type="com.example.databinding.Name" />
   </data>
<LinearLayout
   android:layout_width="match_parent"
   android:orientation="vertical"
   android:layout_height="match_parent"
   tools:context=".MainActivity">

   <EditText
       android:id="@+id/name"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"/>
<TextView
   android:text="@={nithya.names}"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:id="@+id/ts"/>
   <Button
       android:text="submit"
       android:id="@+id/btn"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"/>

</LinearLayout>
</layout>

2.3. MainActivity:

package com.example.databinding

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.databinding.DataBindingUtil
import com.example.databinding.databinding.ActivityMainBinding

class MainActivity : AppCompatActivity() {
lateinit var dataBinding:ActivityMainBinding
   override fun onCreate(savedInstanceState: Bundle?) {
       super.onCreate(savedInstanceState)
       dataBinding = DataBindingUtil.setContentView(this,R.layout.activity_main)
       dataBinding.btn.setOnClickListener{
           Anusha()
       }

   }

   private fun Anusha() {
      // TODO("Not yet implemented")
     val n=dataBinding.name.text.toString()
       val d=Name(n)
       dataBinding.nithya=d
       //dataBinding.ts.text=d.names
     //  dataBinding.ts.text=n
   }
}

2.4. Name.kt

data class Name(var names:String = " ")

2.5. Output:

2.6. Another Example:

2.7. Using DataBinding:

<?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">

    <LinearLayout

        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        tools:context=".MainActivity">

        <Button
            android:id="@+id/plus"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:text="+"
            android:textSize="50dp" />

        <TextView
            android:id="@+id/zero"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="8"
            android:gravity="center"
            android:text="0"
            android:textSize="190dp"

            />

        <Button
            android:id="@+id/minus"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:text="-"
            android:textSize="50dp" />

    </LinearLayout>
</layout>

2.8. MainActivity:

package com.example.databinding2

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.databinding.DataBindingUtil
import com.example.databinding2.databinding.ActivityMainBinding

class MainActivity : AppCompatActivity() {
lateinit var binding:ActivityMainBinding
   var count=0
   override fun onCreate(savedInstanceState: Bundle?) {
       super.onCreate(savedInstanceState)
      binding= DataBindingUtil.setContentView(this,R.layout.activity_main)
       binding.plus.setOnClickListener{
           count++
           binding.zero.text=count.toString()
       }
       binding.minus.setOnClickListener{
           count--
           binding.zero.text=count.toString()
       }
   }
}