AssetsLibrary 实现访问相册,选取多张照片显示

  1 #import "ViewController.h"
  2 #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);
116
117 }