feat: isItemAtIndexVisible

Author: farfromrefug

src/collectionview/collectionview-common.ts

@@ -137,6 +137,7 @@ export abstract class CollectionViewBase extends View implements CollectionViewD
 
     public abstract refresh();
     public abstract refreshVisibleItems();
+    public abstract isItemAtIndexVisible(index:number);
     public abstract scrollToIndex(index: number, animated: boolean);
     public onLayout(left: number, top: number, right: number, bottom: number) {
         super.onLayout(left, top, right, bottom);

src/collectionview/collectionview.android.ts

@@ -774,6 +774,19 @@ export class CollectionView extends CollectionViewBase {
             this._listViewAdapter.notifyItemRangeChanged(first, last - first + 1);
         }
     }
+    public isItemAtIndexVisible(index: number): boolean {
+        const view = this.nativeViewProtected;
+        if (!view) {
+            return false;
+        }
+        const layoutManager = this.layoutManager as androidx.recyclerview.widget.LinearLayoutManager;
+        if (layoutManager['findFirstVisibleItemPosition']) {
+		    const first = layoutManager.findFirstVisibleItemPosition();
+		    const last = layoutManager.findLastVisibleItemPosition();
+		    return index >= first && index <= last;
+        }
+        return false;
+	}
 
     @profile
     public refresh() {

src/collectionview/collectionview.d.ts

@@ -8,6 +8,7 @@ export type Orientation = 'horizontal' | 'vertical';
 export class CollectionView extends CollectionViewBase {
     public refresh();
     public refreshVisibleItems();
+    public isItemAtIndexVisible(index: number): boolean;
     public scrollToIndex(index: number, animated: boolean);
     public getViewForItemAtIndex(index: number): View;
     // on iOS a view is dragged from its center by default

src/collectionview/collectionview.ios.ts

@@ -509,6 +509,15 @@ export class CollectionView extends CollectionViewBase {
             }, null);
         });
     }
+    public isItemAtIndexVisible(itemIndex: number): boolean {
+        const view = this.nativeViewProtected;
+        if (!view) {
+            return false;
+        }
+		const indexes: NSIndexPath[] = Array.from(view.indexPathsForVisibleItems);
+
+		return indexes.some((visIndex) => visIndex.row === itemIndex);
+	}
 
     @profile
     public refresh() {