Fixing crash and Issue 9

NHBalancedFlowLayout/NHBalancedFlowLayout.m

@@ -13,6 +13,10 @@ @interface NHBalancedFlowLayout ()
 {
     CGRect **_itemFrameSections;
     NSInteger _numberOfItemFrameSections;
+
+
+    NSMutableArray *_deleteIndexPaths, *_insertIndexPaths;
+    CGFloat centerXOffset;
 }
 
 @property (nonatomic) CGSize contentSize;
@@ -97,7 +101,7 @@ - (void)prepareLayout
 
     NSMutableArray *headerFrames = [NSMutableArray array];
     NSMutableArray *footerFrames = [NSMutableArray array];
-
+    
     CGSize contentSize = CGSizeZero;
 
     // first release old item frame sections
@@ -107,7 +111,7 @@ - (void)prepareLayout
     _numberOfItemFrameSections = [self.collectionView numberOfSections];
     _itemFrameSections = (CGRect **)malloc(sizeof(CGRect *) * _numberOfItemFrameSections);
 
-    for (int section = 0; section < [self.collectionView numberOfSections]; section++) {
+    for (int section = 0; section < _numberOfItemFrameSections; section++) {
         // add new item frames array to sections array
         NSInteger numberOfItemsInSections = [self.collectionView numberOfItemsInSection:section];
         CGRect *itemFrames = (CGRect *)malloc(sizeof(CGRect) * numberOfItemsInSections);
@@ -126,7 +130,7 @@ - (void)prepareLayout
 
         CGFloat totalItemSize = [self totalItemSizeForSection:section preferredRowSize:idealHeight];
         NSInteger numberOfRows = MAX(roundf(totalItemSize / [self viewPortAvailableSize]), 1);
-
+        
         CGPoint sectionOffset;
         if (self.scrollDirection == UICollectionViewScrollDirectionVertical) {
             sectionOffset = CGPointMake(0, contentSize.height + headerSize.height);
@@ -144,7 +148,7 @@ - (void)prepareLayout
             footerFrame = CGRectMake(contentSize.width + headerSize.width + sectionSize.width, 0, footerSize.width, CGRectGetHeight(self.collectionView.bounds));
         }
         [footerFrames addObject:[NSValue valueWithCGRect:footerFrame]];
-
+        
         if (self.scrollDirection == UICollectionViewScrollDirectionVertical) {
             contentSize = CGSizeMake(sectionSize.width, contentSize.height + headerSize.height + sectionSize.height + footerSize.height);
         }
@@ -157,6 +161,31 @@ - (void)prepareLayout
     self.footerFrames = [footerFrames copy];
 
     self.contentSize = contentSize;
+    CGSize size = self.collectionView.frame.size;
+    centerXOffset = 2* size.width;
+}
+
+- (void)prepareForCollectionViewUpdates:(NSArray *)updateItems {
+    // Keep track of insert and delete index paths
+    [super prepareForCollectionViewUpdates:updateItems];
+
+    _deleteIndexPaths = [NSMutableArray array];
+    _insertIndexPaths = [NSMutableArray array];
+
+    for (UICollectionViewUpdateItem *update in updateItems) {
+        if (update.updateAction == UICollectionUpdateActionDelete) {
+            [_deleteIndexPaths addObject:update.indexPathBeforeUpdate];
+        } else if (update.updateAction == UICollectionUpdateActionInsert) {
+            [_insertIndexPaths addObject:update.indexPathAfterUpdate];
+        }
+    }
+}
+
+- (void)finalizeCollectionViewUpdates {
+    [super finalizeCollectionViewUpdates];
+    // release the insert and delete index paths
+    _deleteIndexPaths = nil;
+    _insertIndexPaths = nil;
 }
 
 - (CGSize)collectionViewContentSize
@@ -167,17 +196,19 @@ - (CGSize)collectionViewContentSize
 - (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
 {
     NSMutableArray *layoutAttributes = [NSMutableArray array];
+    NSInteger n = [self.collectionView numberOfSections];
 
-    for (NSInteger section = 0, n = [self.collectionView numberOfSections]; section < n; section++) {
+    for (NSInteger section = 0; section < n; section++) {
         NSIndexPath *sectionIndexPath = [NSIndexPath indexPathForItem:0 inSection:section];
-
+        
         UICollectionViewLayoutAttributes *headerAttributes = [self layoutAttributesForSupplementaryViewOfKind:UICollectionElementKindSectionHeader
                                                                                                   atIndexPath:sectionIndexPath];
 
-        if (! CGSizeEqualToSize(headerAttributes.frame.size, CGSizeZero) && CGRectIntersectsRect(headerAttributes.frame, rect)) {
+        CGSize size = headerAttributes.frame.size;
+        if (size.height != 0 && size.width != 0 && CGRectIntersectsRect(headerAttributes.frame, rect)) {
             [layoutAttributes addObject:headerAttributes];
         }
-            
+
         for (int i = 0; i < [self.collectionView numberOfItemsInSection:section]; i++) {
             CGRect itemFrame = _itemFrameSections[section][i];
             if (CGRectIntersectsRect(rect, itemFrame)) {
@@ -188,8 +219,8 @@ - (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
 
         UICollectionViewLayoutAttributes *footerAttributes = [self layoutAttributesForSupplementaryViewOfKind:UICollectionElementKindSectionFooter
                                                                                                   atIndexPath:sectionIndexPath];
-
-        if (! CGSizeEqualToSize(footerAttributes.frame.size, CGSizeZero) && CGRectIntersectsRect(footerAttributes.frame, rect)) {
+        size = footerAttributes.frame.size;
+        if (size.width != 0 && size.height != 0 && CGRectIntersectsRect(footerAttributes.frame, rect)) {
             [layoutAttributes addObject:footerAttributes];
         }
     }
@@ -233,6 +264,50 @@ - (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds
     return NO;
 }
 
+- (UICollectionViewLayoutAttributes *)initialLayoutAttributesForAppearingItemAtIndexPath:(NSIndexPath *)itemIndexPath
+{
+    // Must call super
+    UICollectionViewLayoutAttributes *attributes = [super initialLayoutAttributesForAppearingItemAtIndexPath:itemIndexPath];
+
+    if ([_insertIndexPaths containsObject:itemIndexPath]) {
+        // only change attributes on inserted cells
+        if (!attributes)
+            attributes = [self layoutAttributesForItemAtIndexPath:itemIndexPath];
+
+        // Configure attributes ...
+        attributes.alpha = 0.5;
+        CGPoint center = attributes.center;
+        attributes.center = CGPointMake(center.x+centerXOffset, center.y);
+    }
+
+    return attributes;
+}
+
+// Note: name of method changed
+// Also this gets called for all visible cells (not just the deleted ones) and
+// even gets called when inserting cells!
+- (UICollectionViewLayoutAttributes *)finalLayoutAttributesForDisappearingItemAtIndexPath:(NSIndexPath *)itemIndexPath
+{
+    // So far, calling super hasn't been strictly necessary here, but leaving it in
+    // for good measure
+    UICollectionViewLayoutAttributes *attributes = [super finalLayoutAttributesForDisappearingItemAtIndexPath:itemIndexPath];
+
+    if ([_deleteIndexPaths containsObject:itemIndexPath])
+    {
+        // only change attributes on deleted cells
+        if (!attributes)
+            attributes = [self layoutAttributesForItemAtIndexPath:itemIndexPath];
+
+        // Configure attributes ...
+        attributes.alpha = 0.5;
+        CGPoint center = attributes.center;
+        attributes.center = CGPointMake(center.x-centerXOffset, center.y);
+        //attributes.transform3D = CATransform3DMakeScale(0.1, 0.1, 1.0);
+    }
+
+    return attributes;
+}
+
 #pragma mark - Layout helpers
 
 - (CGRect)headerFrameForSection:(NSInteger)section
@@ -253,7 +328,9 @@ - (CGRect)footerFrameForSection:(NSInteger)section
 - (CGFloat)totalItemSizeForSection:(NSInteger)section preferredRowSize:(CGFloat)preferredRowSize
 {
     CGFloat totalItemSize = 0;
-    for (NSInteger i = 0, n = [self.collectionView numberOfItemsInSection:section]; i < n; i++) {
+    NSUInteger n = [self.collectionView.dataSource collectionView:self.collectionView numberOfItemsInSection:section];
+
+    for (NSInteger i = 0; i < n; i++) {
         CGSize preferredSize = [self.delegate collectionView:self.collectionView layout:self preferredSizeForItemAtIndexPath:[NSIndexPath indexPathForItem:i inSection:section]];
 
         if (self.scrollDirection == UICollectionViewScrollDirectionVertical) {
@@ -282,7 +359,34 @@ - (NSArray *)weightsForItemsInSection:(NSInteger)section
 - (void)setFrames:(CGRect *)frames forItemsInSection:(NSInteger)section numberOfRows:(NSUInteger)numberOfRows sectionOffset:(CGPoint)sectionOffset sectionSize:(CGSize *)sectionSize
 {
     NSArray *weights = [self weightsForItemsInSection:section];
-    NSArray *partition = [NHLinearPartition linearPartitionForSequence:weights numberOfPartitions:numberOfRows];
+
+    if (weights.count == 0) {
+        *sectionSize = CGSizeZero;
+        return;
+    }
+
+    NSMutableArray *partition = [NHLinearPartition linearPartitionForSequence:weights numberOfPartitions:numberOfRows];
+
+    // workaround to remove single images in a row
+    for (NSInteger i = 0; i < partition.count; i++) {
+        NSArray *row = partition[i];
+        if (row.count == 1) {
+            NSArray *prev = i > 0 ? partition[i-1] : nil;
+            NSArray *next = i < partition.count-1 ? partition[i+1] : nil;
+            if (prev || next) {
+                // stick the image in the row with less images in it
+                if (next == nil || (prev != nil && prev.count < next.count)) {
+                    partition[i-1] = [prev arrayByAddingObject:row[0]];
+                } else {
+                    NSMutableArray *arr = [next mutableCopy];
+                    [arr insertObject:row[0] atIndex:0];
+                    partition[i+1] = arr;
+                }
+                [partition removeObjectAtIndex:i];
+                i--;
+            }
+        }
+    }
 
     int i = 0;
     CGPoint offset = CGPointMake(sectionOffset.x + self.sectionInset.left, sectionOffset.y + self.sectionInset.top);

NHBalancedFlowLayout/NHLinearPartition.h

@@ -15,6 +15,6 @@
  */
 @interface NHLinearPartition : NSObject
 
-+ (NSArray *)linearPartitionForSequence:(NSArray *)sequence numberOfPartitions:(NSInteger)numberOfPartitions;
++ (NSMutableArray *)linearPartitionForSequence:(NSArray *)sequence numberOfPartitions:(NSInteger)numberOfPartitions;
 
 @end

NHBalancedFlowLayout/NHLinearPartition.m

@@ -75,23 +75,23 @@ + (NSInteger *)linearPartitionTable:(NSArray *)sequence numPartitions:(NSInteger
     return solution;
 }
 
-+ (NSArray *)linearPartitionForSequence:(NSArray *)sequence numberOfPartitions:(NSInteger)numberOfPartitions
++ (NSMutableArray *)linearPartitionForSequence:(NSArray *)sequence numberOfPartitions:(NSInteger)numberOfPartitions
 {
     NSInteger n = [sequence count];
     NSInteger k = numberOfPartitions;
 
-    if (k <= 0) return @[];
+    if (k <= 0) return [NSMutableArray array];
 
     if (k >= n) {
         NSMutableArray *partition = [[NSMutableArray alloc] init];
         [sequence enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
             [partition addObject:@[obj]];
         }];
-        return [partition copy];
+        return [partition mutableCopy];
     }
 
     if (n == 1) {
-        return @[sequence];
+        return [NSMutableArray arrayWithObject:sequence];
     }
 
     // get the solution table
@@ -128,7 +128,7 @@ + (NSArray *)linearPartitionForSequence:(NSArray *)sequence numberOfPartitions:(
 
     [answer insertObject:currentAnswer atIndex:0];
 
-    return [answer copy];
+    return answer;
 }
 
 @end

NHBalancedFlowLayoutDemo/NHBalancedFlowLayoutDemo.xcodeproj/project.pbxproj

@@ -313,7 +313,7 @@
 		50CAF4BC180430A6009A7FA1 /* Project object */ = {
 			isa = PBXProject;
 			attributes = {
-				LastUpgradeCheck = 0500;
+				LastUpgradeCheck = 0720;
 				ORGANIZATIONNAME = "Niels de Hoog";
 				TargetAttributes = {
 					50CAF4E4180430A6009A7FA1 = {
@@ -442,7 +442,6 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
-				ARCHS = "$(ARCHS_STANDARD_INCLUDING_64_BIT)";
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
 				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_MODULES = YES;
@@ -457,6 +456,7 @@
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 				"CODE_SIGN_IDENTITY[sdk=iphoneos*]" = "iPhone Developer";
 				COPY_PHASE_STRIP = NO;
+				ENABLE_TESTABILITY = YES;
 				GCC_C_LANGUAGE_STANDARD = gnu99;
 				GCC_DYNAMIC_NO_PIC = NO;
 				GCC_OPTIMIZATION_LEVEL = 0;
@@ -482,7 +482,6 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				ALWAYS_SEARCH_USER_PATHS = NO;
-				ARCHS = "$(ARCHS_STANDARD_INCLUDING_64_BIT)";
 				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
 				CLANG_CXX_LIBRARY = "libc++";
 				CLANG_ENABLE_MODULES = YES;
@@ -521,6 +520,7 @@
 				GCC_PREFIX_HEADER = "NHBalancedFlowLayoutDemo/NHBalancedFlowLayoutDemo-Prefix.pch";
 				INFOPLIST_FILE = "NHBalancedFlowLayoutDemo/NHBalancedFlowLayoutDemo-Info.plist";
 				IPHONEOS_DEPLOYMENT_TARGET = 6.0;
+				PRODUCT_BUNDLE_IDENTIFIER = "com.invisiblepixel.${PRODUCT_NAME:rfc1034identifier}";
 				PRODUCT_NAME = NHBalancedFlowLayoutDemo;
 				TARGETED_DEVICE_FAMILY = "1,2";
 				WRAPPER_EXTENSION = app;
@@ -536,6 +536,7 @@
 				GCC_PREFIX_HEADER = "NHBalancedFlowLayoutDemo/NHBalancedFlowLayoutDemo-Prefix.pch";
 				INFOPLIST_FILE = "NHBalancedFlowLayoutDemo/NHBalancedFlowLayoutDemo-Info.plist";
 				IPHONEOS_DEPLOYMENT_TARGET = 6.0;
+				PRODUCT_BUNDLE_IDENTIFIER = "com.invisiblepixel.${PRODUCT_NAME:rfc1034identifier}";
 				PRODUCT_NAME = NHBalancedFlowLayoutDemo;
 				TARGETED_DEVICE_FAMILY = "1,2";
 				WRAPPER_EXTENSION = app;
@@ -545,7 +546,6 @@
 		50CAF4FA180430A6009A7FA1 /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
-				ARCHS = "$(ARCHS_STANDARD_INCLUDING_64_BIT)";
 				BUNDLE_LOADER = "$(BUILT_PRODUCTS_DIR)/NHBalancedFlowLayoutDemo.app/NHBalancedFlowLayoutDemo";
 				FRAMEWORK_SEARCH_PATHS = (
 					"$(SDKROOT)/Developer/Library/Frameworks",
@@ -559,6 +559,7 @@
 					"$(inherited)",
 				);
 				INFOPLIST_FILE = "NHBalancedFlowLayoutDemoTests/BalancedFlowLayoutDemoTests-Info.plist";
+				PRODUCT_BUNDLE_IDENTIFIER = "com.invisiblepixel.${PRODUCT_NAME:rfc1034identifier}";
 				PRODUCT_NAME = NHBalancedFlowLayoutDemoTests;
 				TEST_HOST = "$(BUNDLE_LOADER)";
 				WRAPPER_EXTENSION = xctest;
@@ -568,7 +569,6 @@
 		50CAF4FB180430A6009A7FA1 /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
-				ARCHS = "$(ARCHS_STANDARD_INCLUDING_64_BIT)";
 				BUNDLE_LOADER = "$(BUILT_PRODUCTS_DIR)/NHBalancedFlowLayoutDemo.app/NHBalancedFlowLayoutDemo";
 				FRAMEWORK_SEARCH_PATHS = (
 					"$(SDKROOT)/Developer/Library/Frameworks",
@@ -578,6 +578,7 @@
 				GCC_PRECOMPILE_PREFIX_HEADER = YES;
 				GCC_PREFIX_HEADER = "NHBalancedFlowLayoutDemo/NHBalancedFlowLayoutDemo-Prefix.pch";
 				INFOPLIST_FILE = "NHBalancedFlowLayoutDemoTests/BalancedFlowLayoutDemoTests-Info.plist";
+				PRODUCT_BUNDLE_IDENTIFIER = "com.invisiblepixel.${PRODUCT_NAME:rfc1034identifier}";
 				PRODUCT_NAME = NHBalancedFlowLayoutDemoTests;
 				TEST_HOST = "$(BUNDLE_LOADER)";
 				WRAPPER_EXTENSION = xctest;

NHBalancedFlowLayoutDemo/NHBalancedFlowLayoutDemo/NHBalancedFlowLayoutDemo-Info.plist

@@ -9,7 +9,7 @@
 	<key>CFBundleExecutable</key>
 	<string>${EXECUTABLE_NAME}</string>
 	<key>CFBundleIdentifier</key>
-	<string>com.invisiblepixel.${PRODUCT_NAME:rfc1034identifier}</string>
+	<string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
 	<key>CFBundleInfoDictionaryVersion</key>
 	<string>6.0</string>
 	<key>CFBundleName</key>

NHBalancedFlowLayoutDemo/NHBalancedFlowLayoutDemoTests/BalancedFlowLayoutDemoTests-Info.plist

@@ -7,7 +7,7 @@
 	<key>CFBundleExecutable</key>
 	<string>${EXECUTABLE_NAME}</string>
 	<key>CFBundleIdentifier</key>
-	<string>com.invisiblepixel.${PRODUCT_NAME:rfc1034identifier}</string>
+	<string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
 	<key>CFBundleInfoDictionaryVersion</key>
 	<string>6.0</string>
 	<key>CFBundlePackageType</key>

README.md

@@ -3,6 +3,18 @@ NHBalancedFlowLayout
 
 UICollectionViewLayout subclass for displaying items of different sizes in a grid without wasting any visual space. Inspired by: http://www.crispymtn.com/stories/the-algorithm-for-a-perfectly-balanced-photo-gallery
 
+
+## About this Fork
+
+Mainly three differences to the original:
+
+- It fixes the [Issue of upscaled images](https://github.com/njdehoog/NHBalancedFlowLayout/issues/22) wich occurs if the partition algorithm assigns a single item to one row.
+- Incorporates a fix for a crash on `[UICollectionView insertSections:]` from [Pull Request #24](https://github.com/njdehoog/NHBalancedFlowLayout/pull/24)
+- It implements swipe in and out animations, when inserting or removing cells.
+
+
+Hopefully this can be useful for some of you, if you don't want the animations you can easily remove them in the code: [piece 1](https://github.com/graetzer/NHBalancedFlowLayout/blob/master/NHBalancedFlowLayout/NHBalancedFlowLayout.m#L267) and [piece 2](https://github.com/graetzer/NHBalancedFlowLayout/blob/master/NHBalancedFlowLayout/NHBalancedFlowLayout.m#L289).
+
 ## Notes 
 * Tested with iOS 7, but should be compatible with iOS6 as well
 * Works with iPhone and iPad