Adding capability to set final offset after progressive list view upd…

…ates (#685)

* Item container support added

* Added description for renderItemContainer

* version bump

* fixed bug where layout size was ignored on first load by scroll component callback

* adding final update function to progressive list view

* version bump

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

package.json

@@ -1,6 +1,6 @@
 {
   "name": "recyclerlistview",
-  "version": "3.1.0-beta.2",
+  "version": "3.1.0-beta.3",
   "description": "The listview that you need and deserve. It was built for performance, uses cell recycling to achieve smooth scrolling.",
   "main": "dist/reactnative/index.js",
   "types": "dist/reactnative/index.d.ts",

src/core/ProgressiveListView.tsx

@@ -2,9 +2,19 @@ import RecyclerListView, { RecyclerListViewProps, RecyclerListViewState } from "
 export interface ProgressiveListViewProps extends RecyclerListViewProps {
     maxRenderAhead?: number;
     renderAheadStep?: number;
+
+    /**
+     * A smaller final value can help in building up recycler pool in advance. This is only used if there is a valid updated cycle.
+     * e.g, if maxRenderAhead is 0 then there will be no cycle and final value will be unused
+     */
+    finalRenderAheadOffset?: number;
 }
 /**
  * This will incremently update renderAhread distance and render the page progressively.
+ * renderAheadOffset = initial value which will be incremented
+ * renderAheadStep = amount of increment made on each frame
+ * maxRenderAhead = maximum value for render ahead at the end of update cycle
+ * finalRenderAheadOffset = value to set after whole update cycle is completed. If undefined, final offset value will be equal to maxRenderAhead
  */
 export default class ProgressiveListView extends RecyclerListView<ProgressiveListViewProps, RecyclerListViewState> {
     public static defaultProps = {
@@ -43,11 +53,21 @@ export default class ProgressiveListView extends RecyclerListView<ProgressiveLis
                 if (currentRenderAheadOffset < maxContentSize && currentRenderAheadOffset < this.props.maxRenderAhead) {
                     const newRenderAheadOffset = currentRenderAheadOffset + this.props.renderAheadStep;
                     this.updateRenderAheadProgessively(newRenderAheadOffset);
+                } else {
+                    this.performFinalUpdate();
                 }
             }
         }
     }
 
+    private performFinalUpdate(): void {
+        requestAnimationFrame(() => {
+        if (this.props.finalRenderAheadOffset !== undefined) {
+                this.updateRenderAheadOffset(this.props.finalRenderAheadOffset);
+            }
+        });
+    }
+
     private cancelRenderAheadUpdate(): void {
         if (this.renderAheadUdpateCallbackId) {
             cancelAnimationFrame(this.renderAheadUdpateCallbackId);