Data binding to the rescue... or not (?)

KRISTIJAN JURKOVIC

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

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)

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'}

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'

01THE CODE

BIND IT

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

{attachToParent});

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

<?xmlversion="1.0"encoding="utf-8"?><layoutxmlns:android="http://schemas.android.com/apk/res/android"><data><variablename="film"type="co.infinum.starwars.models.Film"/></data><LinearLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical">

<TextViewandroid:id="@+id/title"android:layout_width="match_parent"android:layout_height="wrap_content"android:text="@{film.getTitle()}"android:padding="@dimen/default_spacing"/>

<TextViewandroid:id="@+id/director"android:layout_width="match_parent"android:layout_height="wrap_content"android:text="@{film.getDirector()}"android:padding="@dimen/default_spacing"/>

<TextViewandroid:id="@+id/description"android:layout_width="match_parent"android:layout_height="wrap_content"android:text="@{film.getDescription()}"android:padding="@dimen/default_spacing”/></LinearLayout></layout>

publicclassFilmDetailsActivityextendsBaseActivity{publicstaticfinalStringFILM="film";privateActivityDetailsBindingbinding;privateFilmfilm;

@OverrideprotectedvoidonCreate(BundlesavedInstanceState){super.onCreate(savedInstanceState);binding=DataBindingUtil.setContentView(this,R.layout.activity_details);film=(Film)getIntent().getSerializableExtra(FILM);binding.setFilm(film);}}

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

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

publicclassFilmsAdapterextendsRecyclerView.Adapter<FilmsAdapter.ViewHolder>{{somecodehere}@OverridepublicFilmsAdapter.ViewHolderonCreateViewHolder(ViewGroupparent,intviewType){ListItemMovieBindingbinding=DataBindingUtil.inflate(LayoutInflater.from(context),R.layout.list_item_movie,parent,false);returnnewViewHolder(binding,listener);}

@OverridepublicvoidonBindViewHolder(

FilmsAdapter.ViewHolderholder,intposition){holder.getBinding().setFilm(getItem(position));}

{somecodehere}}

publicstaticclassViewHolderextendsRecyclerView.ViewHolderimplementsView.OnClickListener{

privateListItemMovieBindingbinding;privateOnItemClickListenerlistener;

ViewHolder(ListItemMovieBindingbinding,OnItemClickListenerlistener){

super(binding.getRoot());this.binding=binding;this.listener=listener;binding.getRoot().setOnClickListener(this);}

@OverridepublicvoidonClick(Viewv){if(listener!=null){listener.onItemClick(getAdapterPosition());}}

publicListItemMovieBindinggetBinding(){returnbinding;}}

publicclassFilmextendsBaseObservable{{somecode}@SerializedName("title")privateStringtitle;

@BindablepublicStringgetTitle(){returntitle;}

publicvoidsetTitle(Stringtitle){this.title=title;notifyPropertyChanged(BR.title);}{somecode}}

publicclassFilm{

privatefinalObservableField<String>title=newObservableField<>();}

01IS IT ALL THERE IS?

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)

DYNAMIC BINDINGS

@OverridepublicvoidonBindViewHolder(FilmsAdapter.ViewHolderholder,intposition){finalTitem=items.get(position);holder.getBinding().setVariable(BR.item,item);holder.getBinding().executePendingBindings();}

CUSTOM SETTERS@BindingAdapter("app:imageUrl")publicstaticvoidloadImage(ImageViewview,Stringurl){ Glide.with(context).load(url).into(view);}<layout> <data> <variablename="binder"type="com.example.feed.DummyBinder"/> </data><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:orientation="vertical">

<ImageViewandroid:layout_width="match_parent"android:layout_height="wrap_content"app:imageUrl="@{binder.imageUrl}"/></LinearLayout></layout>

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

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

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

EXAMPLES

• https://github.com/kjurkovic/Hello-Databinding

• https://github.com/ikocijan/Hello-data-binding

Thank you!

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