[Collections] Caches decoration views used in grid layout. Cleans up …

…layout invalidation logic. Summary: Closes https://github.com/google/material-components-ios/issues/479 Reviewers: junius, #mdc_ios_owners Reviewed By: junius, #mdc_ios_owners Projects: #material_components_ios Differential Revision: http://codereview.cc/D808
material-components · May 3, 2016 · 9e37e3a · 9e37e3a
1 parent 5ca5458
commit 9e37e3a
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Showing 2 changed files with 24 additions and 10 deletions.
diff --git a/components/Collections/src/MDCCollectionViewController.m b/components/Collections/src/MDCCollectionViewController.m
@@ -90,9 +90,10 @@ - (void)viewDidLoad {
   _inkTouchController.delaysInkSpread = YES;
 }
 
-- (void)viewDidLayoutSubviews {
-  [super viewDidLayoutSubviews];
-  _styler.shouldInvalidateLayout = NO;
+- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation
+                                duration:(NSTimeInterval)duration {
+  [super willRotateToInterfaceOrientation:toInterfaceOrientation duration:duration];
+  [_collectionViewLayout invalidateLayout];
 }
 
 - (UICollectionViewLayout *)collectionViewLayout {

diff --git a/components/Collections/src/MDCCollectionViewFlowLayout.m b/components/Collections/src/MDCCollectionViewFlowLayout.m
@@ -42,6 +42,7 @@ @implementation MDCCollectionViewFlowLayout {
   NSMutableIndexSet *_insertedSections;
   NSMutableIndexSet *_headerSections;
   NSMutableIndexSet *_footerSections;
+  NSMutableDictionary *_decorationViewAttributeCache;
 }
 
 - (instancetype)init {
@@ -54,6 +55,7 @@ - (instancetype)init {
     self.sectionInset = UIEdgeInsetsZero;
 
     // Register decoration view for grid background.
+    _decorationViewAttributeCache = [NSMutableDictionary dictionary];
     [self registerClass:[MDCCollectionGridBackgroundView class]
         forDecorationViewOfKind:kCollectionDecorationView];
   }
@@ -109,13 +111,17 @@ - (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect {
 }
 
 - (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds {
-  if (!CGSizeEqualToSize(self.collectionView.bounds.size, newBounds.size) ||
-      self.editor.isEditing ||
-      self.styler.cellLayoutType == MDCCollectionViewCellLayoutTypeGrid) {
-    [self invalidateLayout];
+  if (!CGSizeEqualToSize(self.collectionView.bounds.size, newBounds.size)) {
     return YES;
   }
-  return [super shouldInvalidateLayoutForBoundsChange:newBounds];
+  return NO;
+}
+
+- (void)invalidateLayout {
+  [super invalidateLayout];
+
+  // Clear decoration attribute cache.
+  [_decorationViewAttributeCache removeAllObjects];
 }
 
 #pragma mark - UICollectionViewLayout (UISubclassingHooks)
@@ -176,9 +182,16 @@ - (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSInde
 - (UICollectionViewLayoutAttributes *)
     layoutAttributesForDecorationViewOfKind:(NSString *)elementKind
                                 atIndexPath:(NSIndexPath *)indexPath {
+  // Check cache for decoration view attributes, and add to cache if they don't exist.
   MDCCollectionViewLayoutAttributes *decorationAttr =
-      [MDCCollectionViewLayoutAttributes layoutAttributesForDecorationViewOfKind:elementKind
-                                                                   withIndexPath:indexPath];
+      [_decorationViewAttributeCache objectForKey:indexPath];
+  if (!decorationAttr) {
+    decorationAttr =
+        [MDCCollectionViewLayoutAttributes layoutAttributesForDecorationViewOfKind:elementKind
+                                                                     withIndexPath:indexPath];
+    [_decorationViewAttributeCache setObject:decorationAttr forKey:indexPath];
+  }
+
   // Determine section frame by summing all of its item frames.
   CGRect sectionFrame = CGRectNull;
   for (NSInteger i = 0; i < [self numberOfItemsInSection:indexPath.section]; ++i) {