Data Binding with ViewModel in Android
Last Updated : 30 May, 2024
DataBinding is one of the most important concepts to really improve the performance of your Android Application It plays a vital role in the maintenance of the many Android Architectures. In this article, we will learn about DataBinding in ViewModel In Android.
Benefits of integrating Data binding in ViewModel
There are many benefits of using two important concepts of Android Application Development together as mentioned below:
- It provides easy communication between VIEW and its data (or can say View's Data).
- Increase the productivity of developers as it reduces boilerplate codes: As we know the Views are defined in XML files and the XML files are linked with their activity or fragment file, but their data are stored in ViewModel objects. So if the data wants to communicate with the Views, the Activity or Fragment file will act as an intermediate.
So, In this article will we get to how to connect the Views and their Data directly which is there in ViewModel objects.
Step-Step for Data Binding with ViewModel in Android
We will learn this by creating a simple app using Kotlin.
Step 1: Create a New Project in Android Studio
To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio.
Step 2: Enable Data Binding in Application
Create an app with an empty activity. As we are using Data binding we need to enable Data Binding in the build.gradle file
Add a snippet to the build.gradle:
buildFeatures{ dataBinding = true } Step 3: Make Changes in the activity_main.xml file
activity_main.xml is one holding the layout of the whole application. Now we will be adding Data Binding to the Application by adding a layout tag to the activity_main.xml as mentioned below in the CodeBlock.
Here <data> tag can hold the layout variables and layout expressions that will assist us in the whole process.
< layout // all namespaces /> <data> // layout variables/layout expressions </data> // Content of activity_main.xml </layout>
Now we need to create a layout in XML and create a variable in the XML layout. Using a data tag we declare a variable.
XML <?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.ayush.databinding.MainViewModel" /> </data> <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:gravity="center" android:orientation="vertical" android:padding="50dp" tools:context=".MainActivity"> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center_vertical" android:gravity="center_horizontal" android:text="@{ mainViewModel.text }" android:textSize="24sp" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Update text" android:onClick="@{ ()-> mainViewModel.updateText() }"/> </LinearLayout> </layout>
Step 4: Making Changes in the MainAcitivity.kt File
Now, we need to create a binding object in Activity, to pass the data to the variable which we defined in XML layout and MainViewModel object as a data source for the Views.
Below is the MainAcitivity file with the changes to be added:
MainActivity.kt // You need to add your package name here package com.example.data_binding_viewgroup import android.os.Bundle import androidx.activity.enableEdgeToEdge import androidx.appcompat.app.AppCompatActivity import androidx.core.view.ViewCompat import androidx.core.view.WindowInsetsCompat import androidx.databinding.DataBindingUtil import com.example.data_binding_viewgroup.databinding.ActivityMainBinding class MainActivity : AppCompatActivity() { // lateinit variables declared here used // for binding and for storing the ViewModel to // be updated lateinit var binding: ActivityMainBinding lateinit var mainViewModel:MainViewModel override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) enableEdgeToEdge() // Storing the value of extracted in DataBinding binding = DataBindingUtil.setContentView(this,R.layout.activity_main) // Model stored in the variable mainViewModel = MainViewModel() // Data binding the ViewModel binding.mainViewModel = mainViewModel } }
Create a ViewModel class
We want to add Changes in the View Groups all changes are mentioned in a MainViewModel Class which can be used while Data Binding. We Create MainViewModel.kt. by right-clicking and creating Kotlin Class/File name it as MainViewModel.kt.
Navigate to the New Created File:
Add the changes mentioned below:
MainViewModel.kt package com.example.data_binding_viewgroup import androidx.lifecycle.ViewModel class MainViewModel : ViewModel(){ var text = "This is my Application" fun updateText(){ text = "text is Updated" } }
Output:
Github Final Application:
The Final Application Created Can be downloaded from this link - GitHub Link for the Data Binding Android Application
Issues with this Application
Our app is ready and it's also working as we can see the data in form of text which was stored in the ViewModel object. So, we got to know how we directly communicate the View with its Data without taking the help of any intermediate. But, in this app, there is one issue as if we click the UPDATE TEXT button the text won't be updated as expected, but it will remain the same. This is because we need to set the change text ( Data ) again to the View for any new data changes, so we need to define a function in the Activity file to Update the view. But we don't want the communicate the View with Activity.
Solution of the Problem:
So here we can use Live Data, Simply we can say, that Live Data is an observer data holder class. If we declare any data as LiveData, then the data can be observed by Android components like Activity, Fragments, etc. Therefore, if we declare any data as Live Data and bind it using view binding to a View, then whenever the data changes the View gets automatically gets updated. In this article, we have discussed only Data binding with ViewModel and in the next article, we will also see Data Binding with LiveData.
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