Android DataBindings

Post date: Feb 23, 2016 9:49:48 AM

Data binding is an excellent feature introduced in android to implement real MVVM pattern in mobile application developments.

1. Enable data binding

   Open build.gradle and add following configuration in it.

android {

  .....

    dataBinding{

        enabled = true

    }

.....

}

Observable Object:

A POJO class which is extent from BaseObservable object is called as observable object which can be directly bind to any xml files in android

• Getter method of each property fields in this POJO class should have @Bindable annotation

• Setter method of each property field in the POJO class should notify the property change through "notifyPropertyChanged" method.

• "BR" is a auto generated enum for each properity fields which has @Bindable annotation

package bob.bindme.model;

import android.databinding.BaseObservable;

import android.databinding.Bindable;

import bob.bindme.BR;

/**

 * Created by boobalanmunusamy on 2/23/16.

 */

public class CEmployee extends BaseObservable {

    private String userName;

    private String password;

    private String address;

    private String emailAddress;

    @Bindable

    public String getUserName() {

        return userName;

    }

    public void setUserName(String userName) {

        this.userName = userName;

        notifyPropertyChanged(BR.userName);

    }

    @Bindable

    public String getPassword() {

        return password;

    }

    public void setPassword(String password) {

        this.password = password;

        notifyPropertyChanged(BR.password);

    }

    @Bindable

    public String getAddress() {

        return address;

    }

    public void setAddress(String address) {

        this.address = address;

        notifyPropertyChanged(BR.address);

    }

    @Bindable

    public String getEmailAddress() {

        return emailAddress;

    }

    public void setEmailAddress(String emailAddress) {

        this.emailAddress = emailAddress;

        notifyPropertyChanged(BR.emailAddress);

    }

}

2. Move default activity xml codes inside the <layout></layout> tag

Normal Activity XML 

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context="bob.bindme.LoginActivity">

     <LinearLayout

            android:layout_width="match_parent"

            android:layout_height="wrap_content"

            android:orientation="vertical"

            tools:context="bob.bindme.LoginActivity"

            android:layout_centerVertical="true"

            android:layout_alignParentLeft="true"

            android:layout_alignParentStart="true">

            <LinearLayout

                android:orientation="horizontal"

                android:layout_width="match_parent"

                android:layout_height="wrap_content">

                <TextView

                    android:layout_width="0dp"

                    android:layout_weight=".3"

                    android:layout_height="wrap_content"

                    android:textAppearance="?android:attr/textAppearanceSmall"

                    android:text="User Name" android:padding="10dp"

                    android:id="@+id/textView" />

                <EditText

                    android:layout_width="0dp"

                    android:layout_weight=".7"

                    android:layout_height="wrap_content"

                    android:id="@+id/etUserName" />

            </LinearLayout>

            <LinearLayout

                android:orientation="horizontal"

                android:layout_width="match_parent"

                android:layout_height="wrap_content" >

                <TextView

                    android:layout_width="0dp"

                    android:layout_weight=".3"

                    android:layout_height="wrap_content"

                    android:textAppearance="?android:attr/textAppearanceSmall"

                    android:text="Password"

                    android:padding="10dp"

                    android:id="@+id/txtPassword" />

                <EditText

                    android:layout_width="0dp"

                    android:layout_weight=".7"

                    android:layout_height="wrap_content"

                    android:password="true"

                    android:id="@+id/etPassword" />

            </LinearLayout>

            <Button

                android:layout_width="match_parent"

                android:gravity="center"

                android:layout_height="wrap_content"

                android:text="Login"

                android:id="@+id/btnLogin" />

        </LinearLayout>

</RelativeLayout>

Updated XML file has been mentioned below; 

activity_login.xml

<?xml version="1.0" encoding="utf-8"?>

<layout xmlns:android = "http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools">

    <data>

        <variable

            name="employeeInfo"

            type="bob.bindme.model.CEmployee"/>

    </data>

    <RelativeLayout android:layout_width ="match_parent" android:layout_height= "match_parent"

        android:paddingBottom="@dimen/activity_vertical_margin"

        android:paddingLeft="@dimen/activity_horizontal_margin"

        android:paddingRight="@dimen/activity_horizontal_margin"

        android:paddingTop="@dimen/activity_vertical_margin"

        >

        <LinearLayout

            android:layout_width="match_parent"

            android:layout_height="wrap_content"

            android:orientation="vertical"

            tools:context=".activity.LoginActivity"

            android:layout_centerVertical="true"

            android:layout_alignParentLeft="true"

            android:layout_alignParentStart="true">

            <LinearLayout

                android:orientation="horizontal"

                android:layout_width="match_parent"

                android:layout_height="wrap_content">

                <TextView

                    android:layout_width="0dp"

                    android:layout_weight=".3"

                    android:layout_height="wrap_content"

                    android:textAppearance="?android:attr/textAppearanceSmall"

                    android:text="User Name" android:padding="10dp"

                    android:id="@+id/textView" />

                <EditText

                    android:layout_width="0dp"

                    android:layout_weight=".7"

                    android:layout_height="wrap_content"

                    android:text="@{employeeInfo.userName}"

                    android:id="@+id/etUserName" />

            </LinearLayout>

            <LinearLayout

                android:orientation="horizontal"

                android:layout_width="match_parent"

                android:layout_height="wrap_content" >

                <TextView

                    android:layout_width="0dp"

                    android:layout_weight=".3"

                    android:layout_height="wrap_content"

                    android:textAppearance="?android:attr/textAppearanceSmall"

                    android:text="Password"

                    android:padding="10dp"

                    android:id="@+id/txtPassword" />

                <EditText

                    android:layout_width="0dp"

                    android:layout_weight=".7"

                    android:layout_height="wrap_content"

                    android:password="true"

                    android:text="@{employeeInfo.password}"

                    android:id="@+id/etPassword" />

            </LinearLayout>

            <Button

                android:layout_width="match_parent"

                android:gravity="center"

                android:layout_height="wrap_content"

                android:text="Login"

                android:onClick="onLoginButtonClicked"

                android:id="@+id/btnLogin" />

        </LinearLayout>

    </RelativeLayout>

</layout>

Binding Data

By default, a Binding class will be generated based on the name of the layout file, converting it to Pascal case and suffixing “Binding” to it. The above layout file was activity_login.xml so the generate class was ActivityLoginBinding. This class holds all the bindings from the layout properties (e.g. the user variable) to the layout’s Views and knows how to assign values for the binding expressions.The easiest means for creating the bindings is to do it while inflating:

public class LoginActivity extends AppCompatActivity {

    CEmployee cEmployee;

    ActivityLoginBinding activityLoginBinding;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        activityLoginBinding = DataBindingUtil.setContentView(this, R.layout.activity_login);

        cEmployee = new CEmployee();

        activityLoginBinding.setEmployeeInfo(cEmployee);

    }

}