fix: reorder allow to disable reording to certain positions (using itemReorderCheck event)

Author: farfromrefug

src/collectionview/index-common.ts

@@ -105,6 +105,7 @@ export abstract class CollectionViewBase extends View implements CollectionViewD
     public static itemTapEvent = 'itemTap';
     public static displayItemEvent = 'displayItem';
     public static itemReorderedEvent = 'itemReordered';
+    public static itemReorderCheckEvent = 'itemReorderCheck';
     public static itemReorderStartingEvent = 'itemReorderStarting';
     public static itemReorderStartedEvent = 'itemReorderStarted';
     public static loadMoreItemsEvent = 'loadMoreItems';
@@ -559,6 +560,19 @@ export abstract class CollectionViewBase extends View implements CollectionViewD
         this.notify(args);
         this.draggingView = null;
     }
+    _canReorderToPosition(oldPosition, newPosition, item) {
+        const args = {
+            returnValue: true,
+            eventName: CollectionViewBase.itemReorderCheckEvent,
+            object: this,
+            index: oldPosition,
+            item,
+            data: { targetIndex: newPosition },
+            view: this.draggingView
+        } as CollectionViewItemEventData & { returnValue: boolean };
+        this.notify(args);
+        return args.returnValue;
+    }
     _reorderItemInSource(oldPosition: number, newPosition: number, callEvents = true) {
         this.suspendUpdates();
         const ownerSource = this.items as any;

src/collectionview/index.android.ts

@@ -56,11 +56,14 @@ class SimpleCallback extends androidx.recyclerview.widget.ItemTouchHelper.Simple
     ): boolean {
         const startPosition = viewHolder.getAdapterPosition();
         const endPosition = target.getAdapterPosition();
+        const owner = this.owner?.get();
+        if (owner && !owner._canReorderToPosition(startPosition, endPosition, owner.getItemAtIndex(endPosition))) {
+            return false;
+        }
         if (this.startPosition === -1) {
             this.startPosition = startPosition;
         }
         this.endPosition = endPosition;
-        const owner = this.owner?.get();
         if (owner) {
             owner._reorderItemInSource(startPosition, endPosition);
             return true;

src/collectionview/index.ios.ts

@@ -175,11 +175,11 @@ export class CollectionView extends CollectionViewBase {
         return this._map.size;
     }
     onLoaded() {
-        super.onLoaded()
+        super.onLoaded();
         // we need refreshVisibleItems
         // if some items were updated while unloaded they wont re layout
         // after this (because we are not a Layout view)
-        this.refreshVisibleItems()
+        this.refreshVisibleItems();
     }
     eachChild(callback: (child: ViewBase) => boolean) {
         // used for css updates (like theme change)
@@ -472,16 +472,15 @@ export class CollectionView extends CollectionViewBase {
         // this.clearCellSize();
 
         const sizes: NSMutableArray<NSValue> = this._delegate instanceof UICollectionViewDelegateImpl ? this._delegate.cachedSizes : null;
-        const performBatchUpdatesCompletion = (c) =>
-        {   
+        const performBatchUpdatesCompletion = (c) => {
             // if we are not "presented" (viewController hidden) then performBatchUpdatesCompletion would crash
-            const viewIsLoaded =  !!this.page?.viewController ? !!this.page.viewController.view.window : true;
+            const viewIsLoaded = !!this.page?.viewController ? !!this.page.viewController.view.window : true;
             if (viewIsLoaded) {
                 view.performBatchUpdatesCompletion(c, null);
             } else {
                 c();
             }
-        }
+        };
 
         switch (event.action) {
             case ChangeType.Delete: {
@@ -1273,6 +1272,13 @@ class UICollectionViewDelegateImpl extends UICollectionViewCacheDelegateFlowLayo
             owner.scrollViewDidEndScrollingAnimation(scrollView);
         }
     }
+    collectionViewTargetIndexPathForMoveFromItemAtIndexPathToProposedIndexPath(collectionView: UICollectionView, currentIndexPath: NSIndexPath, proposedIndexPath: NSIndexPath): NSIndexPath {
+        const owner = this._owner?.get();
+        if (owner && !owner._canReorderToPosition(currentIndexPath.row, proposedIndexPath.row, owner.getItemAtIndex(proposedIndexPath.row))) {
+            return currentIndexPath;
+        }
+        return proposedIndexPath;
+    }
 }
 
 @NativeClass