DataBinding in Android

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Overview

Android DataBinding is a way to attach user interface with business logic. DataBinding eliminates the way of manual intervention. If there is a change in data, user interface will update automatically. This reduces a lot of boilerplate codes.

Steps to follow

  • Enable databinding in build.gradle (Module) in the android section
 plugins {
    id 'com.android.application'
    id 'kotlin-android'
    id 'kotlin-android-extensions'
    id 'kotlin-kapt'
 }
 buildFeatures {
    dataBinding true
 }
 /*or*/
 dataBinding {
    enabled true
 }
  • Import the dependency in build.gradle (Module) in the dependencies section
 kapt "com.android.databinding:compiler:3.1.4"
  • Enable DataBinding in layout.
 <?xml version="1.0" encoding="utf-8"?>
 <layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <variable
                name="user"
                type="info.androidhive.databinding.User" />
    </data>

    <LinearLayout 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"
            android:orientation="vertical"
            android:padding="@dimen/fab_margin"
            app:layout_behavior="@string/appbar_scrolling_view_behavior"
            tools:context=".MainActivity"
            tools:showIn="@layout/activity_main">

        <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@{user.name}" />

        <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@{user.email}" />

    </LinearLayout>
 </layout>
  • Create an instance of DataBinding in MainActivity with the help of DataBindingUtil.setContentView() method
 class MainActivity : AppCompatActivity()
 {
    private var user : User? = null
    override fun onCreate(savedInstanceState : Bundle?)
    {
        super.onCreate(savedInstanceState)

        // setContentView(R.layout.activity_main);
        val binding : ActivityMainBinding =
            DataBindingUtil.setContentView(this , R.layout.activity_main)
        user = User("Ravi Tamada", "ravi@androidhive.info")
        binding.setUser(user)
    }
 }

Various ways of DataBinding

DataBinding in Activity

 class MainActivity : AppCompatActivity()
 {
    private lateinit var binding : ActivityMainBinding
    override fun onCreate(savedInstanceState : Bundle?)
    {
        super.onCreate(savedInstanceState)
        binding = DataBindingUtil.setContentView(this , R.layout.activity_main)
        binding.tvLabel.text = "Introduction of Data Binding"
    }
 }

Declarative Binding in xml file and Activity

 class MainActivity : AppCompatActivity()
 {
    private lateinit var binding : ActivityMainBinding
    override fun onCreate(savedInstanceState : Bundle?)
    {
        super.onCreate(savedInstanceState)
        binding = DataBindingUtil.setContentView(this , R.layout.activity_main)
        binding.quote = Quote("Hello World!!!", "Raaj Kanchan")
    }
 }
 <?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="quote"
                type="com.example.databinding_android.Quote" />
    </data>

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

        <TextView
                android:id="@+id/tvQuote"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@{quote.quote}"
                android:textSize="18sp"
                android:textStyle="bold"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toTopOf="parent" />

        <TextView
                android:id="@+id/tvAuthor"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginTop="20dp"
                android:text="@{quote.author}"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toBottomOf="@+id/tvQuote" />

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

One Way DataBinding with ViewModel

 class MainActivity : AppCompatActivity()
 {
    private lateinit var binding : ActivityMainBinding
    private lateinit var mainViewModel : MainViewModel
    override fun onCreate(savedInstanceState : Bundle?)
    {
        super.onCreate(savedInstanceState)
        binding = DataBindingUtil.setContentView(this , R.layout.activity_main)
        mainViewModel = ViewModelProvider(this)[MainViewModel::class.java]
        binding.mainViewModel = mainViewModel
        binding.lifecycleOwner = this
    }
 }
 data class Quote(val quote : String , val author : String)
 class MainViewModel : ViewModel()
 {
    private val quotesObject = MutableLiveData(Quote("Life of Stray!" , "Raj Kanchan"))
    val quotesLive : LiveData<Quote>
        get() = quotesObject
    private val releasingObject = MutableLiveData("24th December 2002")
    val releasing : LiveData<String>
        get() = releasingObject

    fun getQuotes()
    {
        quotesObject.value = Quote("Harry Potter and the Goblet of Fire" , "J.K. Rowling")
    }

    fun getReleasingData()
    {
        releasingObject.value = "25th December 2002"
    }
 }
 <?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="mainViewModel"
                type="com.example.databinding_android.MainViewModel" />
    </data>

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

        <!--<EditText
                android:id="@+id/edtReleasingInfo"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:ems="10"
                android:text="@={mainViewModel.releasing}"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toTopOf="parent" />

        <TextView
                android:id="@+id/tvReleasingInfo"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginTop="20dp"
                android:text="@{mainViewModel.releasing}"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toBottomOf="@+id/edtReleasingInfo" />-->

        <TextView
                android:id="@+id/tvQuote"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@{mainViewModel.quotesLive.quote}"
                app:layout_constraintBottom_toTopOf="@+id/tvAuthor"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toTopOf="parent" />

        <TextView
                android:id="@+id/tvAuthor"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@{mainViewModel.quotesLive.author}"
                app:layout_constraintBottom_toTopOf="@id/btnUpdate"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toBottomOf="@id/tvQuote" />

        <Button
                android:id="@+id/btnUpdate"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:onClick="@{() -> mainViewModel.getQuotes()}"
                android:text="Update"
                android:textAllCaps="false"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toBottomOf="@+id/tvAuthor" />

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

References

  1. https://www.vogella.com/tutorials/AndroidDatabinding/article.html
  2. https://www.androidhive.info/android-working-with-databinding/


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