We're checking out new data binding lib announced on the last Google I/O. We'll go in depth of data binding - goals, benefits and drawbacks. Less code should mean less bugs - in theory.

1. Data binding to the
rescue... or not (?)
KRISTIJAN JURKOVIC

2. WHAT IS DATA BINDING?
• Process that establishes a connection between the
application UI and Business logic.
• UI reflects data changes when made
• Announced on the Google I/O 2015

3. REQUIREMENTS
• API level 7+ (Android 2.1 Eclair)
• Android Studio with Android Gradle plugin 1.3.0-beta4 or
higher
• Data binding lib (currently RC)

4. SETUP
Top level build.gradle
dependencies {
classpath 'com.android.tools.build:gradle:1.3.0'
classpath 'com.android.databinding:dataBinder:1.0-rc1'
classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8'
}

5. SETUP
App module build.gradle
dependencies {
...
apt 'com.android.databinding:compiler:1.0-rc0'
}
apply plugin: 'com.android.databinding'
apply plugin: 'com.neenbedankt.android-apt'

6. 01THE CODE

7. BIND IT
• Several ways of binding:
• DataBindingUtil.setContentView({activity}, {layout});
• DataBindingUtil.bind({view});
• DataBindingUtil.inflate({inflater}, {layout}, {parentView},
{attachToParent});

8. WHAT DO WE GET?
• Data binding lib will generate object with name of your
layout in camel case, suffixed with Binding
• list_item_film.xml → ListItemFilmBinding
• on that object we can set variables which are defined in our
layout

9. <?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<data>
<variable name="film" type="co.infinum.starwars.models.Film"/>
</data>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView
android:id="@+id/title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@{film.getTitle()}"
android:padding="@dimen/default_spacing"/>
<TextView
android:id="@+id/director"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@{film.getDirector()}"
android:padding="@dimen/default_spacing"/>
<TextView
android:id="@+id/description"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@{film.getDescription()}"
android:padding="@dimen/default_spacing”/>
</LinearLayout>
</layout>

10. public class FilmDetailsActivity extends BaseActivity {
public static final String FILM = "film";
private ActivityDetailsBinding binding;
private Film film;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
binding = DataBindingUtil
.setContentView(this, R.layout.activity_details);
film = (Film) getIntent().getSerializableExtra(FILM);
binding.setFilm(film);
}
}

11. WHATS WITH THE LISTS
• You can inflate the view in adapter same as in Fragment
• ViewHolder is a bit different that it used to be

12. <?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<data>
<variable name="film"
type="co.infinum.starwars.models.Film" />
</data>
<TextView
android:id="@+id/name"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@{film.getTitle()}"
android:padding="@dimen/default_spacing"/>
</layout>

13. public class FilmsAdapter
extends RecyclerView.Adapter<FilmsAdapter.ViewHolder> {
{ some code here }
@Override
public FilmsAdapter.ViewHolder
onCreateViewHolder(ViewGroup parent, int viewType) {
ListItemMovieBinding binding =
DataBindingUtil.inflate(
LayoutInflater.from(context),
R.layout.list_item_movie,
parent, false);
return new ViewHolder(binding, listener);
}
@Override
public void onBindViewHolder(
FilmsAdapter.ViewHolder holder, int position) {
holder.getBinding().setFilm(getItem(position));
}
{ some code here }
}

14. public static class ViewHolder
extends RecyclerView.ViewHolder
implements View.OnClickListener {
private ListItemMovieBinding binding;
private OnItemClickListener listener;
ViewHolder(ListItemMovieBinding binding,
OnItemClickListener listener) {
super(binding.getRoot());
this.binding = binding;
this.listener = listener;
binding.getRoot().setOnClickListener(this);
}
@Override
public void onClick(View v) {
if (listener != null) {
listener.onItemClick(getAdapterPosition());
}
}
public ListItemMovieBinding getBinding() {
return binding;
}
}

15. public class Film extends BaseObservable {
{some code}
@SerializedName("title")
private String title;
@Bindable
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
notifyPropertyChanged(BR.title);
}
{some code}
}

16. public class Film {
private final ObservableField<String> title = new ObservableField<>();
}

17. 01IS IT ALL THERE IS?

18. NO IT IS NOT
• ObservableCollections
• Event Bindings (OnClick, OnLongClick, etc)
• Dynamic Bindings (for the adapters)
• Custom Setters (for properties which do not have same
name as methods in Java - e.g. padding)

19. DYNAMIC BINDINGS
@Override
public void onBindViewHolder(FilmsAdapter.ViewHolder holder, int position) {
final T item = items.get(position);
holder.getBinding().setVariable(BR.item, item);
holder.getBinding().executePendingBindings();
}

20. CUSTOM SETTERS
@BindingAdapter("app:imageUrl")
public static void loadImage(ImageView view, String url) {
Glide.with(context).load(url).into(view);
}
<layout>
<data>
<variable name="binder" type="com.example.feed.DummyBinder" />
</data>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<ImageView
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:imageUrl="@{binder.imageUrl}" />
</LinearLayout>
</layout>

21. SHOULD WE USE IT?
• You can, on your own risk. - Why?, you ask.
• RC release
• Might contain bugs
• Subject to significant changes which might not be
compatible with your app
• without APT - AS can’t find generated classes

22. HOW SHOULD WE USE IT?
• Databinding allows some kind of logic in layouts
• Databinding allows various imports in the layouts
• Be smart - don’t do it or you’ll have bonding time with AS
debugger when output is not what you desire

23. WHAT TO READ?
• http://developer.android.com/tools/data-binding/
guide.html#custom_binding_class_names
• https://realm.io/news/data-binding-android-boyar-mount/
• https://www.reddit.com/r/androiddev/comments/3f9c3v/
android_data_binding_moves_some_logic_to_xml_is/
• https://code.google.com/p/android/issues/list?can=2&q=Data
+binding&colspec=ID+Type+Status+Owner+Summary
+Stars&cells=tiles

24. EXAMPLES
• https://github.com/kjurkovic/Hello-Databinding
• https://github.com/ikocijan/Hello-data-binding

26. Thank you!
Visit www.infinum.co or find us on social networks:
infinum.co infinumco infinumco infinum