iOS之Photos：访问某个相册通过collectionView显示
文中相关知识点较多，只记载重点思路，相关部分都有对应注释说明，部分还需要优化，只是工作学习的一种思路。
@import AVFoundation;
@import Photos; 导入框架
- (void)viewDidLoad {
[super viewDidLoad];
[self getallAblumInfo];得到相应相册的所有资源
}
- (void)getallAblumInfo{
_localDic = [NSMutableDictionary dictionary];表示对应日期的相应资源集合的键值对
_allKeys = [NSMutableArray array];所有键的集合（目的是字典不会排序，需要通过键值获取对应时间升序的value数组）
PHFetchOptions *options = [[PHFetchOptions alloc]init];
options.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:YES]];通过创建日期升序遍历
PHFetchResult *userCollections = [PHCollection fetchTopLevelUserCollectionsWithOptions:nil];获取用户创建的相册集合
for (PHCollection *c in userCollections) {
if ([c.localizedTitle isEqualToString:@"Test"]) { 条件：集合元数据的相册名为Test
PHAssetCollection *collection = (PHAssetCollection *)c;
PHFetchResult *results = [PHAsset fetchAssetsInAssetCollection:collection options:options];在test相册中通过options条件得到phasset资源集合
NSMutableArray *arr = [NSMutableArray array];
for (int i = 0; i < results.count; i++) {
按时间排序分组
PHAsset *asset1 = results[i];
NSString *str1 = [NSDateFormatter localizedStringFromDate:asset1.creationDate
dateStyle:NSDateFormatterMediumStyle
timeStyle:NSDateFormatterNoStyle];得到资源的年月日
if (i == 0) {
[_allKeys addObject:str1];
[arr addObject:asset1];
[_localDic setObject:arr forKey:str1];
}
if (i > 0) {
PHAsset *asset0 = results[i-1];
NSString *str0 = [NSDateFormatter localizedStringFromDate:asset0.creationDate
dateStyle:NSDateFormatterMediumStyle
timeStyle:NSDateFormatterNoStyle];
if ([str0 isEqualToString:str1]) {
[arr addObject:asset1];
[_localDic setObject:arr forKey:str1];添加元数据到字典
}else{
[_allKeys addObject:str1];
arr = [NSMutableArray array];
[arr addObject:asset1];
[_localDic setObject:arr forKey:str1];
}
}
}
}
}
}
条件2： uicollectionviewdatasource
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
LocalCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:LocalID forIndexPath:indexPath];
PHImageManager *manager = [PHImageManager defaultManager];
if (cell.tag) {
NSLog(@"tag = %ld",cell.tag);
[manager cancelImageRequest:(PHImageRequestID)cell.tag];
}
PHAsset *asset = [_localDic objectForKey:_allKeys[indexPath.section]][indexPath.row];
if (asset.mediaType == PHAssetMediaTypeImage) {资源为图片类型
PHImageRequestOptions *options = [[PHImageRequestOptions alloc]init];
options.resizeMode = PHImageRequestOptionsResizeModeFast;
options.deliveryMode = PHImageRequestOptionsDeliveryModeFastFormat;
options.synchronous = YES;
cell.tag = [manager requestImageForAsset:asset targetSize:CGSizeMake(300, 300) contentMode:PHImageContentModeAspectFit options:options resultHandler:^(UIImage *result, NSDictionary *info) {
cell.contentImg.image = result;获取缩略图
}];
}else if(asset.mediaType == PHAssetMediaTypeVideo){资源为视频类型
cell.tag = [manager requestAVAssetForVideo:asset options:nil resultHandler:^(AVAsset *asset1, AVAudioMix *audioMix, NSDictionary *info) {
AVAssetImageGenerator *generator = [[AVAssetImageGenerator alloc]initWithAsset:asset1];
generator.appliesPreferredTrackTransform = YES;将图片设置为正图
CMTime time = CMTimeMake(0.6, 30);当前时刻的图片
AVAssetImageGeneratorCompletionHandler handler = ^(CMTime requestedTime, CGImageRef image, CMTime actualTime, AVAssetImageGeneratorResult result, NSError *error){
UIImage *thumbImg = [UIImage imageWithCGImage:image];
if (result == AVAssetImageGeneratorSucceeded) {
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
UIGraphicsBeginImageContextWithOptions(cell.contentImg.image.size, NO, 0.0);主线程中合并图片，主要是给缩略图加上一个播放按钮图区分
[thumbImg drawInRect:CGRectMake(0, 0, cell.contentImg.image.size.width, cell.contentImg.image.size.height)];
[[UIImage imageNamed:@"Play"] drawInRect:CGRectMake(cell.contentImg.image.size.width/2-cell.contentImg.image.size.width/6, cell.contentImg.image.size.height/2-cell.contentImg.image.size.height/6, cell.contentImg.image.size.width/3, cell.contentImg.image.size.height/3)];
UIImage *fullImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
cell.contentImg.image = fullImage;
});
}
};
generator.maximumSize = CGSizeMake(200, 200);
[generator generateCGImagesAsynchronouslyForTimes:
[NSArray arrayWithObject:[NSValue valueWithCMTime:time]] completionHandler:handler];
}];
}
return cell;
}
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath{
HeaderCollectionView *reusable = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"headerView" forIndexPath:indexPath];
reusable.lab.text = _allKeys[indexPath.section];设置头视图的日期
NSLog(@"text : %@",reusable.lab.text);
return reusable;
}
UICollectionViewLayoutDelegate 设置头视图的高度（垂直滚动）
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section{
return CGSizeMake(self.view.bounds.size.width, 44);
}
