Gracefully cancel cell reordering when application will resign active notification sent

Author: sibljon

LXReorderableCollectionViewFlowLayout/LXReorderableCollectionViewFlowLayout.m

@@ -85,6 +85,9 @@ - (void)setupCollectionView {
                                                                     action:@selector(handlePanGesture:)];
     _panGestureRecognizer.delegate = self;
     [self.collectionView addGestureRecognizer:_panGestureRecognizer];
+
+    // Useful in multiple scenarios: one common scenario being when the Notification Center drawer is pulled down
+    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleApplicationWillResignActive:) name: UIApplicationWillResignActiveNotification object:nil];
 }
 
 - (id)init {
@@ -303,6 +306,7 @@ - (void)handleLongPressGesture:(UILongPressGestureRecognizer *)gestureRecognizer
 
             [self invalidateLayout];
         } break;
+        case UIGestureRecognizerStateCancelled:
         case UIGestureRecognizerStateEnded: {
             NSIndexPath *currentIndexPath = self.selectedItemIndexPath;
 
@@ -381,6 +385,7 @@ - (void)handlePanGesture:(UIPanGestureRecognizer *)gestureRecognizer {
                 } break;
             }
         } break;
+        case UIGestureRecognizerStateCancelled:
         case UIGestureRecognizerStateEnded: {
             [self invalidatesScrollTimer];
         } break;
@@ -457,6 +462,13 @@ - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(N
     }
 }
 
+#pragma mark - Notifications
+
+- (void)handleApplicationWillResignActive:(NSNotification *)notification {
+    self.panGestureRecognizer.enabled = NO;
+    self.panGestureRecognizer.enabled = YES;
+}
+
 #pragma mark - Depreciated methods
 
 #pragma mark Starting from 0.1.0