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Infinum Android Talks #14 - Data binding to the rescue... or not (?) by Kristijan Jurkovic

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Infinum
Infinum

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.

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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
<?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>
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); } }
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
<?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>
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 } }
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; } }
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} }
public class Film { private final ObservableField<String> title = new ObservableField<>(); }
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 @Override public void onBindViewHolder(FilmsAdapter.ViewHolder holder, int position) { final T item = items.get(position); holder.getBinding().setVariable(BR.item, item); holder.getBinding().executePendingBindings(); }
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>
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
Infinum Android Talks #14 - Data binding to the rescue... or not (?) by Kristijan Jurkovic
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Infinum Android Talks #14 - Data binding to the rescue... or not (?) by Kristijan Jurkovic