/* |
Copyright (C) 2014 Apple Inc. All Rights Reserved. |
See LICENSE.txt for this sample’s licensing information |
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Abstract: |
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A view controller displaying a grid of assets. |
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*/ |
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#import "AAPLAssetGridViewController.h" |
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#import "AAPLGridViewCell.h" |
#import "AAPLAssetViewController.h" |
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@import Photos; |
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@implementation NSIndexSet (Convenience) |
- (NSArray *)aapl_indexPathsFromIndexesWithSection:(NSUInteger)section { |
NSMutableArray *indexPaths = [NSMutableArray arrayWithCapacity:self.count]; |
[self enumerateIndexesUsingBlock:^(NSUInteger idx, BOOL *stop) { |
[indexPaths addObject:[NSIndexPath indexPathForItem:idx inSection:section]]; |
}]; |
return indexPaths; |
} |
@end |
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@implementation UICollectionView (Convenience) |
- (NSArray *)aapl_indexPathsForElementsInRect:(CGRect)rect { |
NSArray *allLayoutAttributes = [self.collectionViewLayout layoutAttributesForElementsInRect:rect]; |
if (allLayoutAttributes.count == 0) { return nil; } |
NSMutableArray *indexPaths = [NSMutableArray arrayWithCapacity:allLayoutAttributes.count]; |
for (UICollectionViewLayoutAttributes *layoutAttributes in allLayoutAttributes) { |
NSIndexPath *indexPath = layoutAttributes.indexPath; |
[indexPaths addObject:indexPath]; |
} |
return indexPaths; |
} |
@end |
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@interface AAPLAssetGridViewController () <PHPhotoLibraryChangeObserver> |
@property (strong) IBOutlet UIBarButtonItem *addButton; |
@property (strong) PHCachingImageManager *imageManager; |
@property CGRect previousPreheatRect; |
@end |
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@implementation AAPLAssetGridViewController |
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static NSString * const CellReuseIdentifier = @"Cell"; |
static CGSize AssetGridThumbnailSize; |
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- (void)awakeFromNib |
{ |
self.imageManager = [[PHCachingImageManager alloc] init]; |
[self resetCachedAssets]; |
[[PHPhotoLibrary sharedPhotoLibrary] registerChangeObserver:self]; |
} |
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- (void)dealloc |
{ |
[[PHPhotoLibrary sharedPhotoLibrary] unregisterChangeObserver:self]; |
} |
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- (void)viewWillAppear:(BOOL)animated |
{ |
[super viewWillAppear:animated]; |
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CGFloat scale = [UIScreen mainScreen].scale; |
CGSize cellSize = ((UICollectionViewFlowLayout *)self.collectionViewLayout).itemSize; |
AssetGridThumbnailSize = CGSizeMake(cellSize.width * scale, cellSize.height * scale); |
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if (!self.assetCollection || [self.assetCollection canPerformEditOperation:PHCollectionEditOperationAddContent]) { |
self.navigationItem.rightBarButtonItem = self.addButton; |
} else { |
self.navigationItem.rightBarButtonItem = nil; |
} |
} |
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- (void)viewDidAppear:(BOOL)animated |
{ |
[super viewDidAppear:animated]; |
[self updateCachedAssets]; |
} |
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- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender |
{ |
NSIndexPath *indexPath = [self.collectionView indexPathForCell:sender]; |
AAPLAssetViewController *assetViewController = segue.destinationViewController; |
assetViewController.asset = self.assetsFetchResults[indexPath.item]; |
assetViewController.assetCollection = self.assetCollection; |
} |
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#pragma mark - PHPhotoLibraryChangeObserver |
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- (void)photoLibraryDidChange:(PHChange *)changeInstance |
{ |
// Call might come on any background queue. Re-dispatch to the main queue to handle it. |
dispatch_async(dispatch_get_main_queue(), ^{ |
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// check if there are changes to the assets (insertions, deletions, updates) |
PHFetchResultChangeDetails *collectionChanges = [changeInstance changeDetailsForFetchResult:self.assetsFetchResults]; |
if (collectionChanges) { |
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// get the new fetch result |
self.assetsFetchResults = [collectionChanges fetchResultAfterChanges]; |
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UICollectionView *collectionView = self.collectionView; |
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if (![collectionChanges hasIncrementalChanges] || [collectionChanges hasMoves]) { |
// we need to reload all if the incremental diffs are not available |
[collectionView reloadData]; |
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} else { |
// if we have incremental diffs, tell the collection view to animate insertions and deletions |
[collectionView performBatchUpdates:^{ |
NSIndexSet *removedIndexes = [collectionChanges removedIndexes]; |
if ([removedIndexes count]) { |
[collectionView deleteItemsAtIndexPaths:[removedIndexes aapl_indexPathsFromIndexesWithSection:0]]; |
} |
NSIndexSet *insertedIndexes = [collectionChanges insertedIndexes]; |
if ([insertedIndexes count]) { |
[collectionView insertItemsAtIndexPaths:[insertedIndexes aapl_indexPathsFromIndexesWithSection:0]]; |
} |
NSIndexSet *changedIndexes = [collectionChanges changedIndexes]; |
if ([changedIndexes count]) { |
[collectionView reloadItemsAtIndexPaths:[changedIndexes aapl_indexPathsFromIndexesWithSection:0]]; |
} |
} completion:NULL]; |
} |
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[self resetCachedAssets]; |
} |
}); |
} |
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#pragma mark - UICollectionViewDataSource |
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- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section |
{ |
NSInteger count = self.assetsFetchResults.count; |
return count; |
} |
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- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath |
{ |
AAPLGridViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:CellReuseIdentifier forIndexPath:indexPath]; |
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// Increment the cell's tag |
NSInteger currentTag = cell.tag + 1; |
cell.tag = currentTag; |
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PHAsset *asset = self.assetsFetchResults[indexPath.item]; |
[self.imageManager requestImageForAsset:asset |
targetSize:AssetGridThumbnailSize |
contentMode:PHImageContentModeAspectFill |
options:nil |
resultHandler:^(UIImage *result, NSDictionary *info) { |
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// Only update the thumbnail if the cell tag hasn't changed. Otherwise, the cell has been re-used. |
if (cell.tag == currentTag) { |
cell.thumbnailImage = result; |
} |
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}]; |
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return cell; |
} |
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#pragma mark - UIScrollViewDelegate |
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- (void)scrollViewDidScroll:(UIScrollView *)scrollView |
{ |
[self updateCachedAssets]; |
} |
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#pragma mark - Asset Caching |
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- (void)resetCachedAssets |
{ |
[self.imageManager stopCachingImagesForAllAssets]; |
self.previousPreheatRect = CGRectZero; |
} |
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- (void)updateCachedAssets |
{ |
BOOL isViewVisible = [self isViewLoaded] && [[self view] window] != nil; |
if (!isViewVisible) { return; } |
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// The preheat window is twice the height of the visible rect |
CGRect preheatRect = self.collectionView.bounds; |
preheatRect = CGRectInset(preheatRect, 0.0f, -0.5f * CGRectGetHeight(preheatRect)); |
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// If scrolled by a "reasonable" amount... |
CGFloat delta = ABS(CGRectGetMidY(preheatRect) - CGRectGetMidY(self.previousPreheatRect)); |
if (delta > CGRectGetHeight(self.collectionView.bounds) / 3.0f) { |
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// Compute the assets to start caching and to stop caching. |
NSMutableArray *addedIndexPaths = [NSMutableArray array]; |
NSMutableArray *removedIndexPaths = [NSMutableArray array]; |
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[self computeDifferenceBetweenRect:self.previousPreheatRect andRect:preheatRect removedHandler:^(CGRect removedRect) { |
NSArray *indexPaths = [self.collectionView aapl_indexPathsForElementsInRect:removedRect]; |
[removedIndexPaths addObjectsFromArray:indexPaths]; |
} addedHandler:^(CGRect addedRect) { |
NSArray *indexPaths = [self.collectionView aapl_indexPathsForElementsInRect:addedRect]; |
[addedIndexPaths addObjectsFromArray:indexPaths]; |
}]; |
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NSArray *assetsToStartCaching = [self assetsAtIndexPaths:addedIndexPaths]; |
NSArray *assetsToStopCaching = [self assetsAtIndexPaths:removedIndexPaths]; |
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[self.imageManager startCachingImagesForAssets:assetsToStartCaching |
targetSize:AssetGridThumbnailSize |
contentMode:PHImageContentModeAspectFill |
options:nil]; |
[self.imageManager stopCachingImagesForAssets:assetsToStopCaching |
targetSize:AssetGridThumbnailSize |
contentMode:PHImageContentModeAspectFill |
options:nil]; |
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self.previousPreheatRect = preheatRect; |
} |
} |
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- (void)computeDifferenceBetweenRect:(CGRect)oldRect andRect:(CGRect)newRect removedHandler:(void (^)(CGRect removedRect))removedHandler addedHandler:(void (^)(CGRect addedRect))addedHandler |
{ |
if (CGRectIntersectsRect(newRect, oldRect)) { |
CGFloat oldMaxY = CGRectGetMaxY(oldRect); |
CGFloat oldMinY = CGRectGetMinY(oldRect); |
CGFloat newMaxY = CGRectGetMaxY(newRect); |
CGFloat newMinY = CGRectGetMinY(newRect); |
if (newMaxY > oldMaxY) { |
CGRect rectToAdd = CGRectMake(newRect.origin.x, oldMaxY, newRect.size.width, (newMaxY - oldMaxY)); |
addedHandler(rectToAdd); |
} |
if (oldMinY > newMinY) { |
CGRect rectToAdd = CGRectMake(newRect.origin.x, newMinY, newRect.size.width, (oldMinY - newMinY)); |
addedHandler(rectToAdd); |
} |
if (newMaxY < oldMaxY) { |
CGRect rectToRemove = CGRectMake(newRect.origin.x, newMaxY, newRect.size.width, (oldMaxY - newMaxY)); |
removedHandler(rectToRemove); |
} |
if (oldMinY < newMinY) { |
CGRect rectToRemove = CGRectMake(newRect.origin.x, oldMinY, newRect.size.width, (newMinY - oldMinY)); |
removedHandler(rectToRemove); |
} |
} else { |
addedHandler(newRect); |
removedHandler(oldRect); |
} |
} |
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- (NSArray *)assetsAtIndexPaths:(NSArray *)indexPaths |
{ |
if (indexPaths.count == 0) { return nil; } |
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NSMutableArray *assets = [NSMutableArray arrayWithCapacity:indexPaths.count]; |
for (NSIndexPath *indexPath in indexPaths) { |
PHAsset *asset = self.assetsFetchResults[indexPath.item]; |
[assets addObject:asset]; |
} |
return assets; |
} |
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#pragma mark - Actions |
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- (IBAction)handleAddButtonItem:(id)sender |
{ |
// Create a random dummy image. |
CGRect rect = rand() % 2 == 0 ? CGRectMake(0, 0, 400, 300) : CGRectMake(0, 0, 300, 400); |
UIGraphicsBeginImageContextWithOptions(rect.size, NO, 1.0f); |
[[UIColor colorWithHue:(float)(rand() % 100) / 100 saturation:1.0 brightness:1.0 alpha:1.0] setFill]; |
UIRectFillUsingBlendMode(rect, kCGBlendModeNormal); |
UIImage *image = UIGraphicsGetImageFromCurrentImageContext(); |
UIGraphicsEndImageContext(); |
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// Add it to the photo library |
[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{ |
PHAssetChangeRequest *assetChangeRequest = [PHAssetChangeRequest creationRequestForAssetFromImage:image]; |
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if (self.assetCollection) { |
PHAssetCollectionChangeRequest *assetCollectionChangeRequest = [PHAssetCollectionChangeRequest changeRequestForAssetCollection:self.assetCollection]; |
[assetCollectionChangeRequest addAssets:@[[assetChangeRequest placeholderForCreatedAsset]]]; |
} |
} completionHandler:^(BOOL success, NSError *error) { |
if (!success) { |
NSLog(@"Error creating asset: %@", error); |
} |
}]; |
} |
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@end |
