iOS开发之获取系统相册ALAssetLibrary

注：当你选择看这篇博客时想必你的应用还支持iOS8一下系统，如果你的应用要求最低版本大于iOS8，建议使用PhotoKit框架，效率更高

ALAssetsLibrary包含，ALAssetsLibrary，ALAssetsGroup，ALAsset，ALAssetsFilter，ALAssetRepresentation几个类

1、框架解析

(1) ALAssetsLibrary

ALAssetsLibrary类可以实现查看相册列表，增加相册，保存图片到相册等功能

具体实现见框架使用

(2) ALAssetsGroup

ALAssetsGroup就是相册的类，可以通过ALAssetsLibrary遍历得到相册ALAssetsGroup

通过valueForProperty:获取相册名称

[assetsGroup valueForProperty:ALAssetsGroupPropertyName]

ALAssetsGroup 可以使用setAssetsFilter:(ALAssetsFilter *)filter过滤照片或者视频详情见ALAssetsFilter

(3) ALAsset

ALAsset就是一个资源文件，一个ALAssetsGroup下会有多个资源文件，获取相册和视频就是通过ALAssetsLibrary遍历得到相册ALAssetsGroup，

然后通过ALAssetsGroup遍历得到资源文件ALAsset

通过valueForProperty:获取资源文件的信息：

//查看资源的文件类型

[asset valueForProperty:ALAssetPropertyType]

//查看资源的文件类型

[asset valueForProperty:ALAssetPropertyType]

//查看资源的地理位置信息
 [asset valueForProperty:ALAssetPropertyLocation]
 //如果资源是视频，查看视频的时长
  [asset valueForProperty:ALAssetPropertyDuration]
 //查看资源的方向，图片的旋转方向
 [asset valueForProperty:ALAssetPropertyOrientation]
  //查看资源的创建时间
 [asset valueForProperty:ALAssetPropertyDate]
  //查看资源的描述信息
  [asset valueForProperty:ALAssetPropertyRepresentations]
  //查看资源的url路径
  [asset valueForProperty:ALAssetPropertyAssetURL]

通过 asset.defaultRepresentation 可以获取资源文件的url、size、name等信息

// 获取资源文件url

asset.defaultRepresentation.url

// 获取资源文件大小

asset.defaultRepresentation.size

// 获取资源文件名称

asset.defaultRepresentation.filename

(4) ALAssetsFilter

ALAssetsFilter主要用于过滤图片和视频

通过setAssetsFilter:筛选资源文件

//筛选图片和视频

[group setAssetsFilter:[ALAssetsFilter allAssets]];

//筛选图片

[group setAssetsFilter:[ALAssetsFilter allPhotos]];

//筛选视频

[group setAssetsFilter:[ALAssetsFilter allVideos]];

(5) ALAssetRepresentation

ALAsset类有一个defaultRepresentation方法，返回值是ALAssetRepresentation类，该类的作用就是获取该资源图片的详细资源信息。

通过representation 获取资源文件信息

// //获取资源图片的详细资源信息

ALAssetRepresentation* representation = [asset defaultRepresentation];

//获取资源图片的长宽

CGSize dimension = [representation dimensions];

//获取资源图片的高清图

[representation fullResolutionImage];

//获取资源图片的全屏图

[representation fullScreenImage];

//获取资源图片的名字

NSString* filename = [representation filename]; NSLog(@"filename:%@",filename);

//缩放倍数

[representation scale];

//图片资源容量大小

[representation size];

//图片资源原数据

[representation metadata];

//旋转方向

[representation orientation];

//资源图片url地址，该地址和ALAsset通过ALAssetPropertyAssetURL获取的url地址是一样的

[representation url];

//资源图片uti，唯一标示符

[representation UTI]

2、框架使用

（1）遍历得到图片视频资源

ALAssetsLibrary *assetsLibrary = [[ALAssetsLibrary alloc] init]

[assetsLibrary enumerateGroupsWithTypes:ALAssetsGroupAll  usingBlock:resultsBlock  failureBlock:nil];

ALAssetsLibraryGroupsEnumerationResultsBlock resultsBlock = ^(ALAssetsGroup *group, BOOL *stop) {

NSString * str = [group valueForProperty:ALAssetsGroupPropertyName];

// 得到相册

if (group){

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

// 得到资源文件

if (asset) {

NSString *type = [asset valueForProperty:ALAssetPropertyType];

if ([type isEqual:ALAssetTypePhoto] )

{

dispatch_async(dispatch_get_global_queue(0, 0), ^{

[self addAssetWith:asset title:[self.assetsGroup valueForProperty:ALAssetsGroupPropertyName]];

});

self.numberOfPhotos ++;

AddFileSelectModel *assetSelectModel = [[AddFileSelectModel alloc] init];

assetSelectModel.asset = asset;

assetSelectModel.selected = NO;

NSDate *date = [assetSelectModel.asset valueForProperty:ALAssetPropertyDate];

NSTimeInterval time = date.timeIntervalSince1970;

assetSelectModel.date = (NSInteger)time;

NSDateFormatter* formatter = [[NSDateFormatter alloc] init];

[formatter setDateFormat:@"yyyy-MM-dd HH:MM:ss"];

NSString *str = [formatter stringFromDate:[NSDate dateWithTimeIntervalSince1970:time]];

NSLog(@"%@",str);

[self.assets addObject:assetSelectModel];

self.assets = [[[self.assets reverseObjectEnumerator] allObjects] mutableCopy];

dispatch_async(dispatch_get_main_queue(), ^{

[self.collectionView reloadData];

});

}

}

}

}];

}

};

（2）在系统相册中创建相册

- (void)createAlbumInPhone

{

ALAssetsLibrary *assetsLibrary = [[ALAssetsLibrary alloc] init];

NSMutableArray *groups=[[NSMutableArray alloc]init];

ALAssetsLibraryGroupsEnumerationResultsBlock listGroupBlock = ^(ALAssetsGroup *group, BOOL *stop) {

if (group) {

[groups addObject:group];

} else {

BOOL haveHDRGroup = NO;

for (ALAssetsGroup *gp in groups) {

NSString *name =[gp valueForProperty:ALAssetsGroupPropertyName];

if ([name isEqualToString:@"联系家庭云"]) {

haveHDRGroup = YES;

}

}

if (!haveHDRGroup) {

[assetsLibrary addAssetsGroupAlbumWithName:@"联系家庭云" resultBlock:^(ALAssetsGroup *group) {

[groups addObject:group];

} failureBlock:nil];

haveHDRGroup = YES;

}

}

};

//创建相簿

[assetsLibrary enumerateGroupsWithTypes:ALAssetsGroupAlbum usingBlock:listGroupBlock failureBlock:nil];

}

（3）在系统相册中保存图片

- (void)saveImageToAlbum:(UIImage *)image

{

[self saveToAlbumWithMetadata:nil imageData:UIImageJPEGRepresentation(image,1.0) customAlbumName:@"联系家庭云" completionBlock:^{

// 创建成功执行成功代码

} failureBlock:^(NSError *error) {

//处理添加失败的方法显示alert让它回到主线程执行，不然那个框框死活不肯弹出来

dispatch_async(dispatch_get_main_queue(), ^{

//添加失败一般是由用户不允许应用访问相册造成的，这边可以取出这种情况加以判断一下

if([error.localizedDescription rangeOfString:@"User denied access"].location != NSNotFound ||[error.localizedDescription rangeOfString:@"用户拒绝访问"].location!=NSNotFound){

UIAlertView *alert=[[UIAlertView alloc]initWithTitle:error.localizedDescription message:error.localizedFailureReason delegate:nil cancelButtonTitle:NSLocalizedString(@"ok", nil) otherButtonTitles: nil];

[alert show];

}

});

}];

}

- (void)saveToAlbumWithMetadata:(NSDictionary *)metadata imageData:(NSData *)imageData customAlbumName:(NSString *)customAlbumName completionBlock:(void (^)(void))completionBlock failureBlock:(void (^)(NSError *error))failureBlock

{

ALAssetsLibrary *assetsLibrary = [[ALAssetsLibrary alloc] init];

void (^AddAsset)(ALAssetsLibrary *, NSURL *) = ^(ALAssetsLibrary *assetsLibrary, NSURL *assetURL) {

[assetsLibrary assetForURL:assetURL resultBlock:^(ALAsset *asset) {

[assetsLibrary enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:^(ALAssetsGroup *group, BOOL *stop) {

if ([[group valueForProperty:ALAssetsGroupPropertyName] isEqualToString:customAlbumName]) {

[group addAsset:asset];

if (completionBlock) {

completionBlock();

}

}

} failureBlock:^(NSError *error) {

if (failureBlock) {

failureBlock(error);

}

}];

} failureBlock:^(NSError *error) {

if (failureBlock) {

failureBlock(error);

}

}];

};

[assetsLibrary writeImageDataToSavedPhotosAlbum:imageData metadata:metadata completionBlock:^(NSURL *assetURL, NSError *error) {

if (customAlbumName) {

[assetsLibrary addAssetsGroupAlbumWithName:customAlbumName resultBlock:^(ALAssetsGroup *group) {

if (group) {

[assetsLibrary assetForURL:assetURL resultBlock:^(ALAsset *asset) {

[group addAsset:asset];

if (completionBlock) {

completionBlock();

}

} failureBlock:^(NSError *error) {

if (failureBlock) {

failureBlock(error);

}

}];

} else {

AddAsset(assetsLibrary, assetURL);

}

} failureBlock:^(NSError *error) {

AddAsset(assetsLibrary, assetURL);

}];

} else {

if (completionBlock) {

completionBlock();

}

}

}];

}