Data Binding - Android by Harin Trivedi

Data Binding
with Android Studio
by
Harin Trivedi
Sr. Software Engineer

OBJECTIVE
➔ Automatic & Dynamic
view binding
➔ Binding data to view
component
◆ Static binding
◆ Dynamic binding

How to enable it ?
Just add below lines of code in app
level build.gradle file.
➔ Available on and above Android
2.1 (Level 7)
➔ Need ‘Android Gradle Plugin’
2.0.0 and above.
➔ After Gradle version 3.1.0 add this
in gradle.properties
android.databinding.enableV2=true
android {
...
dataBinding {
enabled = true
}
}

View Component
binding of
Layout
Need to place layout with root tag
<layout>
<layout
xmlns:android="http://schemas.android.com/apk/res/android">
<data>
… // Model to binding
</data>
… // Your layout
</layout>

Generate Binding
Three ways to generate dynamic binding to attached java class
1. Activity
1. Fragment or Other (eg. Adapter row layout)
MainActivityBinding Binding =
DataBindingUtil.setContentView(this,R.layout.main_activity);
OR
MainActivityBinding binding = MainActivityBinding.inflate(getLayoutInflater());
FragmentListBinding binding = DataBindingUtil.inflate(layoutInflater,
R.layout.fragment_list, viewGroup, false);

Binding Data (Model)
Include model class variable inside <data> tag to use in layout
<layout>
<data>
<variable name="user" type="com.example.User"/>
</data>
<LinearLayout ...>
<TextView ...
android:text="@{user.firstName}"/>
<TextView ...
android:text="@{user.lastName}"/>
</LinearLayout>
</layout>
public class User {
private final String firstName;
private final String lastName;
public User(String firstName, String lastName) {
this.firstName = firstName;
this.lastName = lastName;
}
public String getFirstName() {
return this.firstName; }
public String getLastName() {
return this.lastName; }
}

Event Binding
➔ Method Reference :- Direct reference to events (eg. onClick, onItemClick etc.)
➔ Listener Binding :- Reference to event handler (eg. presenter)
android:onClick="@{listener::onClick}"
<CheckBox … android:onCheckedChanged=
"@{(cb, isChecked) ->
presenter.toggleSubscribe(task, isChecked)}"
android:onClick=
"()->presenter.onSaveClick(task)"
public class Presenter {
public void onSaveClick(Task task){}
public void onCompletedChanged(Task task, boolean completed){} }

Injecting Multiple
Type of Data
<data>
<import type="com.example.User"/>
<import type="java.util.List"/>
<import
type="android.graphics.drawable.Drawable"/>
...
<variable name="user"
type="com.example.User"/>
<variable name="image" type="Drawable"/>
<variable name="note" type="String"/>
<variable name="userList"
type="List<User>"/>
</data>
Note :- Auto import is not yet supported.
➔ Primitive Type Objects
◆ Int, float, string etc.
➔ Model
◆ User defined or System class
objects
➔ Collections
◆ List, Map etc.
➔ Drawables
etc.

Include
<include
android:id="+@id/inner_layout_id"
layout="@layout/inner_layout"
bind:user="@{user}"/>
Need to pass bound data to the
included layout.
MainActivityBinding mainBinding;
InnerLayoutBinding innerBinding;
...
innerBinding =
mainBinding.innerLayoutId;
innerBinding.tvTitle.setText(“Hello”);

Expression Language
&
Operators
Examples:
android:visibility="@{age < 18 ? View.GONE :
View.VISIBLE}"
android:visibility="@{item.isFavourite ?
View.VISIBLE : View.GONE}"
android:text="@{user.firstname + ‘ ’ +
user.lastname}"
android:text="@{String.valueOf(index + 1)}"
android:transitionName="@{‘image_’ + id}"

Attribute Setters
1. Automatic Setters
1. Renamed Setters
If you want ‘itemBackgroundColor’ instead ‘background color’
android:text="@{tiem.title}" // looks for setTitle() in user object
android:background="@{item.bgColor}" // looks for setTitle() in user object
@BindingMethods({
@BindingMethod(type = "android.widget.ImageView",
attribute = "android:background",
method = "setItemBackgroundColor")
})
Public void setItemBackgroundColor(int color) { … }
android:background=
"@{item.itemBackgroundColor}"

Custom Setters (Binding Adapter)
More than setting value, process view and/or apply logic on data.
Public class BindingUtils{
@BindingAdapter({"bind:imageUrl", "bind:error"})
public static void loadImage(ImageView view, String url, Drawable error) {
Picasso.with(view.getContext()).load(url).error(error).into(view);
}
}
<ImageView … app:imageUrl="@{item.imageUrl}"
app:error="@{@drawable/errorDrawable}"/>

Observables
➔ Observable Objects
➔ Observable Fields
➔ Observable Collections
https://developer.android.com/topic/
libraries/data-
binding/index.html#data_objects
➔ Suitable for MVVM
approach.
The real power of data binding can
be used by giving your data objects
the ability to
notify
when
data changes.

Before I forget ...
Two Way Binding
<layout>
<data>
<variable name="user" type="com.example.User"/>
</data>
<LinearLayout ...>
<EditText …
android:text="@={user.firstName}"/>
<EditText …
android:text="@={user.lastName}"/>
</LinearLayout>
</layout>

References
● https://developer.android.com/topic/libr
aries/data-binding/index.html
● https://medium.com/google-
developers/android-data-binding-
recyclerview-db7c40d9f0e4#.n53rmdvsf
● Blog Series:
https://medium.com/@Harry91/android-data-
binding-binding-view-and-data-part-1-
3b9154de09c6
● Github Demo:
https://github.com/HarinTrivedi/MyDataBindin
gExample-master

Data Binding - Android by Harin Trivedi

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