Android ViewModel Data Binding Tutorial

Data Binding:

As define in Android developer,

The Data Binding Library is a support library that allows you to bind UI components in your layouts
to data sources in your app using a declarative format rather than programmatically.

Now use data binding on the layout which we created on ViewModel example,

(No any changes in step 1, step 2 and Step 3).

Let us assume, we are showing EMPLOYEE data on screen,

To implement ViewModel,

Step 1:

Create a DataModel class,

public class User {

  public String empId;

  public String empName;

 

  public User(String empId, String empName) {

      this.empId = empId;

      this.empName = empName;

  

  }

  public String getEmpId() {

      return empId;

  }

  public void setEmpId(String empId) {

      this.empId = empId;

  }

  public String getEmpName() {

      return empName;

  }

  public void setEmpName(String empName) {

      this.empName = empName;

  }

}

Step 2:

Create a Repository, which will communicate between ViewModel and Data,

public class MainActivityRepo {

  private static MainActivityRepo instance;

  private ArrayList<User> dataset=new ArrayList<>();

  public static MainActivityRepo getInstance(){

      if(instance==null){

          instance=new MainActivityRepo();

      }

      return instance;

  }

  public MutableLiveData<List<User>> getUser(){

      setUserData();

      MutableLiveData<List<User>> data=new MutableLiveData<>();

      data.setValue(dataset);

      return data;

  }

  private void setUserData(){

      dataset.add(

              new User("emp001","John Doe","http://lorempixel.com/400/200/sports/1/"));

      dataset.add(

              new User("emp002","Ray Ban","http://lorempixel.com/400/200/sports/2/"));

      dataset.add(

              new User("emp003","Don Brown","http://lorempixel.com/400/200/sports/3/"));

  }

Step 3:

Create ViewModel,

public class MainActivityViewModel extends ViewModel {

  private MutableLiveData<List<User>> users;

  private MainActivityRepo mRepo;

  public void init(){

      if(users!=null){

          return;

      }

      mRepo=MainActivityRepo.getInstance();

      users=mRepo.getUser();

  }

  public LiveData<List<User>> getUser(){

      if(users==null){

          users=new MutableLiveData<List<User>>();

      }

      return users;

  }

}

Step 4:

Create a layout xml, with <layout> parent tag,

<?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="empDetail"

 type="com.mpvtest.jetapplication.oneWayBinding.oneWayBinding.dataModel.User"/>

   </data>

<RelativeLayout

      android:layout_width="match_parent"

      android:layout_height="match_parent"

      tools:context=".oneWayBinding.oneWayBinding.MainActivity">

  <TextView

           android:id="@+id/tv_empId"

          android:layout_width="match_parent"

          android:layout_height="wrap_content"

android:text="@{empDetail.empId}"

           />

</RelativeLayout>

</layout>

Now build your project, it will generate DataBinding class,

For eg: if layout name is activity_main, then the generated dataBinding class name will be,

ActivityMainBinding

Step 5:

Create a MainActivity class,

Now remove setContentView,

We have to use DataBindingUtil.setContentView ,

And we will free our code from using findViewById also.

public class MainActivityJv extends AppCompatActivity {

   @Override

  protected void onCreate(@Nullable Bundle savedInstanceState) {

      super.onCreate(savedInstanceState);

      //setContentView(R.layout.activity_main);

    binding= DataBindingUtil.setContentView(this, R.layout.activity_main);

      MainActivityViewModel model = ViewModelProviders.of(this)

                                      .get(MainActivityViewModel.class);

      model.init();

      model.getUser().observe(this, new Observer<List<User>>() {

          @Override

          public void onChanged(@Nullable List<User> users) {

              changeUI(users);

          }});

  }

  private void changeUI(List<User> user){

/** can get all user data from loop**/

//        for(int i=0;i<user.size();i++){

//         // Log.d("data:value",user.get(i).empId);

//

//        }

 //    TextView tv_empId=findViewById(R.id.tv_empId);

 //   tv_empId.setText(user.get(0).empId);

binding.setEmpDetail(user.get(0));

binding.invalidateAll();

  }

}

Now benefit the data binding.ccc

find the sample project in Github