A custom Kotlin delegate for initializing ViewDataBinding objects for Android databinding

ActivityBindingProvider.kt

/**
 * Provides a [ViewDataBinding] object of the declared type by
 * calling [DataBindingUtil.setContentView] with the property owning [Activity] and the specified
 * layout resource id
 */
class ActivityBindingProvider<out T : ViewDataBinding>(
        @LayoutRes private val layoutRes: Int) : ReadOnlyProperty<Activity, T> {

    private var binding : T? = null

    override operator fun getValue(thisRef: Activity, property: KProperty<*>): T {
        return binding ?: createBinding(thisRef).also{ binding = it }
    }

    private fun createBinding(activity: Activity):T {
        return DataBindingUtil.setContentView(activity, layoutRes)
    }
}

FooActivity.kt

class FooActivity : Activity {
  val binding:ActivityFooBinding by ActivityBindingProvider(R.layout.activity_foo)
}