Kotlin & Android Data Binding Library

1. Kotlin & Android Data Binding Library @takuji31
2. @takuji31 (Takuji Nishibayashi) Application Engineer at Hatena
3. Loves Kotlin
4. Kotlin 1.0.1-2 released
5. Android Data Binding Library
6. Official binding library for Android
7. Android Studio support
8. One way binding support
9. Two way binding support latest version
10. Can use with Kotlin
11. Define binding using layout XML
12. Auto generate binding class
13. Define binding <layout>
 <data>
 <import type="android.view.View" />
 <variable name=“user" type="jp.takuji31.kotlindatabinding.DataClassActivity.User" />
 <variable name=“randomButtonClickListener” type="android.view.View.OnClickListener" />
 </data>
 <RelativeLayout>
 <TextView android:text="Name : "/>
 <TextView android:text="@{user.name}" tools:text="namename" />
 <TextView android:text="Birthday : "
 android:visibility="@{user.birthDay != null ? View.VISIBLE : View.GONE}" />
 <TextView android:text=“@{user.birthDay}" tools:text="1970/01/01"
 android:visibility="@{user.birthDay != null ? View.VISIBLE : View.GONE}” />
 <Button android:onClick="@{randomButtonClickListener}"/>
 </RelativeLayout>
 </layout>
14. Using binding class DataClassActivity : AppCompatActivity() {
 data class User(val name: String, val birthDay: String?)
 var users = listOf(
 User(name = "takuji31", birthDay = "1987/03/01"),
 User(name = "takuji32", birthDay = "1987/03/02"),
 User(name = "takuji33", birthDay = "1987/03/03"),
 User(name = "takuji24884", birthDay = null)
 )
 val binding: ActivityDataClassBinding by lazy {
 DataBindingUtil.setContentView<ActivityDataClassBinding>(this, R.layout.activity_data_class)
 }
 override fun onCreate(savedInstanceState: Bundle?) {
 binding.user = users.last()
 binding.randomButtonClickListener = View.OnClickListener {
 binding.user = users[0]
 users = users.drop(1) + binding.user
 }
 }
 }
15. No more (ViewClass)findById(R.id.viewId)
16. Define binding <layout>
 
 <android.support.v7.widget.RecyclerView
 android:id="@+id/recyclerView"
 android:layout_width="match_parent"
 android:layout_height="match_parent"/>
 </layout>
17. Field access class MainActivity : AppCompatActivity() {
 val binding : ActivityMainBinding by lazy {DataBindingUtil.setContentView<ActivityMainBinding>(this, R.layout.activity_main)} 
 override fun onCreate(savedInstanceState: Bundle?) {
 super.onCreate(savedInstanceState)
 binding.recyclerView.layoutManager = LinearLayoutManager(this)
 }
 }
18. Property observer
19. Observable data class class Counter : BaseObservable() {
 @get:Bindable
 var count : Int = 0
 set(value) {
 field = value
 notifyPropertyChanged(BR.count)
 }
 }

20. Define binding <layout>
 <data>
 <variable name=“counter" type=“…PropertyObserverActivity.Counter” />
 <variable name="buttonClickListener"
 type="android.view.View.OnClickListener" />
 </data>
 <LinearLayout>
 <TextView android:text="@{@string/count_format(counter.count)}"/>
 <Button android:onClick=“@{buttonClickListener}" />
 </LinearLayout>
 </layout>

21. Change value class PropertyObserverActivity : AppCompatActivity() {
 val binding : ActivityPropertyObserverBinding by lazy { DataBindingUtil.setContentView( this, R.layout.activity_property_observer ) } 
 override fun onCreate(savedInstanceState: Bundle?) {
 val counter = Counter()
 binding.counter = counter
 binding.buttonClickListener = View.OnClickListener {
 counter.count += 1 }
 }
 }
22. Binding adapter
23. Define binding adapter object Adapters {
 @JvmStatic
 @BindingAdapter("android:text")
 fun convertZonedDateTimeToString (textView: TextView, zonedDateTime : ZonedDateTime) {
 val timeString = zonedDateTime.format( DateTimeFormatter.ofPattern("yyyy/MM/dd/ HH:mm:SS"))
 textView.text = timeString
 }
 }
24. Value converter
25. Issues with Kotlin
26. Can’t find converter written with Kotlin
27. Use Java
28. example : github.com/ takuji31/KotlinDataBinding
29. Enjoy Data Binding Life