1. 添加绑定设置

如上一篇文章（Android - DataBinding）一样，在 build.gradle 中添加

buildFeatures{
    dataBinding true
}

2. 添加数据类

添加数据类 User.java：

public class User {
    public String userName;

    public User(String userName) {
        this.userName = userName;
    }
}

3. 添加ViewModel

添加 UserViewModel.java：

public class UserViewModel {
    private ObservableField<User> userObservableField;

    public UserViewModel() {
        User user = new User("Jack");
        userObservableField = new ObservableField<>();
        userObservableField.set(user);
    }

    public String getUserName(){
        return userObservableField.get().userName;
    }

    public void setUserName(String userName){
        Log.d("UserViewModel", "userObservableField: " + userName);
        userObservableField.get().userName = userName;
    }
}

4. activity_main.xml添加绑定

<?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="userViewModel"
            type="com.example.databinding2.UserViewModel" />
    </data>

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

        <EditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            tools:text="用户名"
            android:text="@={userViewModel.userName}"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

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

5. MainActivity.java添加绑定

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.activity_main);

        ActivityMainBinding activityMainBinding = DataBindingUtil.setContentView(this, R.layout.activity_main);
        activityMainBinding.setUserViewModel(new UserViewModel());
    }
}