Data Binding and Kotlin

In this session you'll dive deeper into the Data Binding library and learn some Kotlin tips and tricks.

1. Data Binding and Kotlin ETON OTIENO @eton_otieno @CodeZilla7
2. Project Set Up
3. Converting existing layouts to data binding layouts
4. Converting existing layouts to data binding layouts
5. The Expression Language  Data Binding provides expressions which can be used in your layouts.  Use them minimally because placing logic in your layouts makes testing impossible.  There are some useful ones like the null coalescing operator and the ternary operand. The null coalescing operator choses the left operand if it isn’t null or the right if the left is null.
6. The Expression Language Data binding also supports using imports in your layouts
7. Binding your data to views  Let’s create a model with the data we require.  By using a data class you get methods like toString(), equals() , hashCode() and copy() automatically, you don’t have to override them.
8. Binding your data to views
9. Binding your data to views
10. Binding your data to views  As I had earlier said, you shouldn’t put complex logic in your XML, instead use ViewModels. It’s testable and you’ll get to write more Kotlin code.  You can get a reference to the ViewModel using the variable tag in your layout.
11. Binding your data to views
12. Cleaning up with Kotlin
13. Cleaning up with Kotlin
14. Data Binding Adapters Data binding adapters are responsible for calling the appropriate framework methods to set the values of your layout views. You can also define custom attributes in your XML layouts with custom binding adapters.
15. Data Binding Adapters  Hold on for a second, what type of attribute is errorImage?  This is one of the many parts of data binding that really shines.  With custom binding adapters, you don’t have to write custom attributes in your custom view; just use a binding adapter.
16. Data Binding Adapters  Let’s say for example you have a setImageShadowBackground(Int) in your custom view, you can use the attribute imageShadowBackground attribute in your layout!
17. Data Binding Adapters
18. Data Binding Adapters  Data binding will call the appropriate function in your custom view.  This also works with the android framework classes that have setter methods but no layout attributes. The DrawerLayout is a good example.
19. Data Binding Adapters  So, how can you use the attributes I showed you earlier on? Let’s write some Kotlin code!
20. Data Binding Adapters If you prefer using an object instead of declaring the binding adapter as a top level function, remember to annotate the function as @JvmStatic
21. Learning Resources  https://github.com/googlesamples/android-databinding  https://developer.android.com/topic/libraries/data-binding/  https://androidstudy.com/2018/04/11/android-data-binding/
22. Thank You! I had a great time being your data binding sensei for this session!