1 #import <AssetsLibrary/AssetsLibrary.h>  3   4   5 /**  6  *  ALAssetsLibrary.h 代表资源库(所有的视频,照片)  7     ALAssetsGroup.h   代表资源库中的相册  8     ALAsset.h         代表相册中一个视频或者一张照片  9     ALAssetRepresentation.h 代表一个资源的描述,可以获取到原始图片 10  */ 11  12 @interface ViewController () 13  14 @property (weak, nonatomic) IBOutlet UICollectionView *collectionView; 15  16 @property (nonatomic,strong)NSMutableArray *array; 17 @end 18  19 @implementation ViewController{ 20  21     ALAssetsLibrary *library; 22  23 } 24  25 - (void)viewDidLoad { 26     [super viewDidLoad]; 27      28     //创建可变数组,存储资源文件 29     _array = [NSMutableArray array]; 30      31     //创建资源库,用于访问相册资源 32     library = [[ALAssetsLibrary alloc] init]; 33      34     //遍历资源库中所有的相册,有多少个相册,usingBlock会调用多少次 35     [library enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos usingBlock:^(ALAssetsGroup *group, BOOL *stop) { 36          37         //如果存在相册,再遍历 38         if (group) { 39              40             //遍历相册中所有的资源(照片,视频) 41            [group enumerateAssetsUsingBlock:^(ALAsset *result, NSUInteger index, BOOL *stop) { 42                 43                /* 44                 资源的索引 45                if (index == 2) { 46                     47                 //停止遍历 48                    *stop = YES; 49                } 50                 */ 51                 52                if (result) { 53                    //将资源存储到数组中 54                    [_array addObject:result]; 55                } 56                 57            }]; 58         } 59          60         //刷新_collectionView reloadData; 61          [_collectionView reloadData]; 62          63     } failureBlock:^(NSError *error) { 64          65         NSLog(@"访问失败"); 66     }]; 67      68 } 69  70 #pragma mark -UICollectionViewDelegate 71  72 //行的个数 73 - (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section { 74  75  76     return _array.count; 77  78 } 79  80 //创建UICollectionViewCell 81 - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath { 82      83     //如果单元格是在故事版中画出来的,不需要注册,需要在单元格中指定标识符 84     UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"cell" forIndexPath:indexPath]; 85      86     //取得图片视图 87     UIImageView *imgView = (UIImageView *)[cell.contentView viewWithTag:1]; 88      89     //取出对应的资源数据 90      ALAsset *result =_array[indexPath.row]; 91      92     //获取到缩略图 93     CGImageRef cimg = [result thumbnail]; 94      95     //转换为UIImage 96     UIImage *img = [UIImage imageWithCGImage:cimg]; 97  98     //显示图片 99     imgView.image = img;100     101     /**102      *  获取到原始图片103      ALAssetRepresentation *presentation = [result defaultRepresentation];104     105     CGImageRef resolutionImg = [presentation fullResolutionImage];106      */107 108     return cell;109 110 }111 112 //单元格大小113 - (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath{114 115     return CGSizeMake(70, 70);