ALAssets的两种用法

一：

ALAssetsGroupEnumerationResultsBlock resultsBlock = ^(ALAsset *result, NSUInteger index, BOOL *stop) {

if (result && [[result valueForProperty:ALAssetPropertyType] isEqual:ALAssetTypePhoto]) {

ZWPhoto *aPhoto = [[ZWPhoto alloc] initWithAsset:result];

aPhoto.checked = false;

aPhoto.originPhotoNeeded = false;

[self.photosArray addObject:aPhoto];

} else if (self.photosArray.count > 0) {

[self.collectionView reloadData];

}

};

[self.assetsGroup enumerateAssetsUsingBlock:resultsBlock];

二：

self.assetsLibrary = [[ALAssetsLibrary alloc] init];

dispatch_queue_t dispatchQueue =dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

dispatch_async(dispatchQueue, ^(void) {

// 遍历所有相册

[self.assetsLibrary enumerateGroupsWithTypes:ALAssetsGroupAll

usingBlock:^(ALAssetsGroup *group, BOOL *stop) {

// 遍历每个相册中的项ALAsset

[group enumerateAssetsUsingBlock:^(ALAsset *result, NSUInteger index,BOOL *stop) {

__block BOOL foundThePhoto = NO;

if (foundThePhoto){

*stop = YES;

}

// ALAsset的类型

NSString *assetType = [result valueForProperty:ALAssetPropertyType];

if ([assetType isEqualToString:ALAssetTypePhoto]){

foundThePhoto = YES;

*stop = YES;

ALAssetRepresentation *assetRepresentation =[result defaultRepresentation];

CGFloat imageScale = [assetRepresentation scale];

UIImageOrientation imageOrientation = (UIImageOrientation)[assetRepresentation orientation];

dispatch_async(dispatch_get_main_queue(), ^(void) {

CGImageRef imageReference = [assetRepresentation fullResolutionImage];

// 对找到的图片进行操作

UIImage *image =[[UIImage alloc] initWithCGImage:imageReference scale:imageScale orientation:imageOrientation];

_myImageView = [[UIImageView alloc] initWithFrame:CGRectMake(100, 100, 200, 200)];

_myImageView.image = image;

[self.view addSubview:_myImageView];

if (image != nil){

//获取到第一张图片

} else {

NSLog(@"Failed to create the image.");

} });

}

}];

}

failureBlock:^(NSError *error) {

NSLog(@"Failed to enumerate the asset groups.");

}];

});