Advanced Android DataBinding

Talk at GDG Düsseldorf November MeetUp (2016-11-24).

Among Android Developers, the introduction of DataBinding is considered as one of „the most significant changes“ to the Android framework. It impacts the whole way how developers develop and design their apps. The basic usage of DataBinding is pretty straightforward. However, in advanced use cases the usage could be tricky. How to generically bind data in RecyclerViews? How to test DataBinding? What are BindingAdapters for? Which architectural style to choose for DataBinding? ...

This talk tries to answer these kind of questions by providing a closer look to this new tool. It addresses advanced challenges developers will stumble upon when applying DataBinding in real world projects. I'm using DataBinding since day one and already gained some practical experiences which might be interesting for other Android enthusiast as well. However, while one objective of the talk is to share my experience I would also like to facilitate a discussion among the attendees and also learn from their experiences with DataBinding.

Transcript

1. Advanced Android DataBinding André Diermann q2ad a11n GDG Düsseldorf
2. “DataBinding is one of the most significant changes to the Android Framework.”
3. Agenda • Basics • Hands-on • Migration • Architecture • Testing
4. What? DataBinding is a tool which drastically reduces the amount of boilerplate code. It helps you to do more with less code.
5. How? android { dataBinding { enabled = true } } build.gradle
6. How? <?xml version="1.0" encoding="utf-8"?> <layout xmlns:android="…"> <data> <variable name="user" type="…"/> </data> <TextView … android:text="@{user.name}"/> </layout> main_activity.xml
7. How? <?xml version="1.0" encoding="utf-8"?> <layout xmlns:android="…"> <data> <variable name="user" type="…"/> </data> <TextView … android:text="@{user.name}"/> </layout> main_activity.xml
8. How? <?xml version="1.0" encoding="utf-8"?> <layout xmlns:android="…"> <data> <variable name="user" type="…"/> </data> <TextView … android:text="@{user.name}"/> </layout> main_activity.xml
9. How? <?xml version="1.0" encoding="utf-8"?> <layout xmlns:android="…"> <data> <variable name="user" type="…"/> </data> <TextView … android:text="@{user.name}"/> </layout> main_activity.xml
10. How? @Override protected void onCreate(…) { … MainActivityBinding binding = DataBindingUtil.setContentView( this, R.layout.main_activity); binding.setUser(user); } ActivityMain.java
11. How? @Override protected void onCreate(…) { … MainActivityBinding binding = DataBindingUtil.setContentView( this, R.layout.main_activity); binding.setUser(user); } ActivityMain.java
12. How? @Override protected void onCreate(…) { … MainActivityBinding binding = DataBindingUtil.setContentView( this, R.layout.main_activity); binding.setUser(user); } ActivityMain.java
13. Features • Code generation • View references • Variables • Custom setters • Custom conversions • Event handling • Observability • Two-way binding • Expression language • …
14. Hands-on • Lists • User interaction • Data changes
15. Lists <android.support.v7.widget.RecyclerView bind:data="@{listData}" bind:layout="@{@layout/list_item}" /> Generic data
16. User interaction <Button … android:onClick="@{()->vm.onClick()}" /> Events <EditText android:text="@={vm.text}" /> Two-way
17. Data changes public class MyViewModel implements ViewModel { public final ObservableField<String> string; public final ObservableBoolean boolean; public final ObservableList<ListViewModel> list; … } Dynamic data Further reading: https://medium.com/google-developers/android-data-binding-observability-9de4ff3fe038
18. https://github.com/a11n/devfest-2016-realm
19. Migration
20. Migration
21. Migration Button button = (Button) findViewById( R.id.button); button.setOnClickListener(…); Before 1. Eliminate findViewById()* * or any third party library binding.button. setOnClickListener(…); After
22. Migration button.setOnClickListener( new OnClickListener(){ @Override onClick(…){ handler.onClick(…); } } ); Before 2. Remove event listeners <Button android:onClick= “@{handler::onClick}“ /> After
23. Migration User user = loadUser(); tvUserName.setText(user.getName()); if (user.getPicture() == null) ivUserPic.setVisibility(…); … Before 3. Bind data to UI binding.setUser(user); <TextView android:text=“@{user.name}“ /> <ImageView android:visibility=“@{user.picture}“ /> After
24. Migration 1. Eliminate findViewById() 2. Remove event listeners 3. Bind data to UI 4. Adapt your architecture
25. Architecture MVVM VIEW VIEW MODEL MODEL (Business Logic) • Binding • Entities • Interactors
26. 1. Activity or Fragment • Load Binding • Create ViewModel • Inject Interactors into ViewModel • Inject ViewModel into Binding VIEW 2. ViewModel • Load Model via Interactor • Bind Model data to ViewModel fields VIEW MODEL MODEL (Business Logic) 3. There is no step 3 ;-)
27. Testing • Don‘t test the generated code • Test your ViewModels • Verify UI with Espresso
28. Conclusion • DataBinding has great potential for faster and cleaner app dev. • Using its full potential requires architecture changes • It’s not meant for everything! • Some controversy voices exist