Fix DatabindingPresenter 'leak'

Author: natario1

library/src/main/kotlin/com/otaliastudios/elements/Presenter.kt

@@ -180,20 +180,20 @@ public abstract class Presenter<T: Any>(
      */
     public class Holder(view: View): RecyclerView.ViewHolder(view) {
 
-        private val map: MutableMap<String, Any> = mutableMapOf()
+        private val map: MutableMap<String, Any?> = mutableMapOf()
 
         /**
          * Sets an object to be held by this Holder. Might be a view,
          * or any other object you need to attach.
          */
-        public fun set(key: String, value: Any) { map[key] = value }
+        public fun set(key: String, value: Any?) { map[key] = value }
 
         /**
          * Returns an object that was previously attached to this
          * holder using [set].
          */
         @Suppress("UNCHECKED_CAST")
-        public fun <T: Any> get(key: String): T = map[key] as T
+        public fun <T> get(key: String): T = map[key] as T
 
         /**
          * Shorthand for itemViewType.

library/src/main/kotlin/com/otaliastudios/elements/extensions/DataBindingPresenter.kt

@@ -4,6 +4,9 @@ import android.content.Context
 import android.view.View
 import android.view.ViewGroup
 import androidx.databinding.ViewDataBinding
+import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.LifecycleObserver
+import androidx.lifecycle.OnLifecycleEvent
 import com.otaliastudios.elements.Element
 import com.otaliastudios.elements.Page
 import com.otaliastudios.elements.Presenter
@@ -23,9 +26,15 @@ abstract class DataBindingPresenter<T: Any, DB: ViewDataBinding>(
 
     final override fun onCreate(parent: ViewGroup, elementType: Int): Holder {
         val binding = onCreateBinding(parent, elementType)
-        binding.setLifecycleOwner(this) // Is this the right thing to do?
+        binding.setLifecycleOwner(this)
         val holder = Holder(binding.root)
         holder.set("binding", binding)
+        lifecycle.addObserver(object: LifecycleObserver {
+            @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
+            fun onDestroy() {
+                binding.setLifecycleOwner(null)
+            }
+        })
         return holder
     }