Expose scrollable nodes (#690)

* PLV now render after first onLayout

* ..

* scrollable node now a public API

Co-authored-by: Talha Naqvi <talha.naqvi@shopify.com>

src/core/RecyclerListView.tsx

@@ -353,6 +353,13 @@ export default class RecyclerListView<P extends RecyclerListViewProps, S extends
         });
     }
 
+    public getScrollableNode(): number | null {
+        if (this._scrollComponent && this._scrollComponent.getScrollableNode) {
+          return this._scrollComponent.getScrollableNode();
+        }
+        return null;
+    }
+
     public renderCompat(): JSX.Element {
         //TODO:Talha
         // const {

src/core/scrollcomponent/BaseScrollComponent.tsx

@@ -20,4 +20,9 @@ export interface ScrollComponentProps {
 }
 export default abstract class BaseScrollComponent extends React.Component<ScrollComponentProps, {}> {
     public abstract scrollTo(x: number, y: number, animate: boolean): void;
+
+    //Override and return node handle to your custom scrollview. Useful if you need to use Animated Events.
+    public getScrollableNode(): number | null {
+        return null;
+    }
 }

src/platform/reactnative/scrollcomponent/ScrollComponent.tsx

@@ -43,6 +43,13 @@ export default class ScrollComponent extends BaseScrollComponent {
         }
     }
 
+    public getScrollableNode(): number | null {
+        if (this._scrollViewRef && this._scrollViewRef.getScrollableNode) {
+          return this._scrollViewRef.getScrollableNode();
+        }
+        return null;
+    }
+
     public render(): JSX.Element {
         const Scroller = TSCast.cast<ScrollView>(this.props.externalScrollView); //TSI
         const renderContentContainer = this.props.renderContentContainer ? this.props.renderContentContainer : this._defaultContainer;