【iOS开发】---- 如何将图片保存至自定义分组
一般我们照片存储都是直接存储在相机胶卷中，调用下面的方法就可以了：
1. void UIImageWriteToSavedPhotosAlbum (
2. UIImage *image,
3. id completionTarget,
4. SEL completionSelector,
5. void *contextInfo
6. );
但是如果我们想将图片存储到自定义的分组该怎么做呢，我查了一下ALAssetsLibrary的文档，发现没有相应的方法，好吧，google一下，发现了一篇文章：点击打开链接。
作者的解决思路如下：
1.将图片先保存到相机胶卷中；
2.在相机胶卷中找到这个图片所创建的AlAsset；
3.将此AlAsset添加到你需要存放的自定义分组中。
主要代码如下所示，注释也很清楚了：
1. -(void)saveImage:(UIImage*)image toAlbum:(NSString*)albumName withCompletionBlock:(SaveImageCompletion)completionBlock
2. {
3. //write the image data to the assets library (camera roll)
4. [self writeImageToSavedPhotosAlbum:image.CGImage orientation:(ALAssetOrientation)image.imageOrientation
5. completionBlock:^(NSURL* assetURL, NSError* error) {
6.
7. //error handling
8. if (error!=nil) {
9. completionBlock(error);
10. return;
11. }
12.
13. //add the asset to the custom photo album
14. [self addAssetURL: assetURL
15. toAlbum:albumName
16. withCompletionBlock:completionBlock];
17.
18. }];
19. }
1. -(void)addAssetURL:(NSURL*)assetURL toAlbum:(NSString*)albumName withCompletionBlock:(SaveImageCompletion)completionBlock
2. {
3. __block BOOL albumWasFound = NO;
4.
5. //search all photo albums in the library
6. [self enumerateGroupsWithTypes:ALAssetsGroupAlbum
7. usingBlock:^(ALAssetsGroup *group, BOOL *stop) {
8.
9. //compare the names of the albums
10. if ([albumName compare: [group valueForProperty:ALAssetsGroupPropertyName]]==NSOrderedSame) {
11.
12. //target album is found
13. albumWasFound = YES;
14.
15. //get a hold of the photo's asset instance
16. [self assetForURL: assetURL
17. resultBlock:^(ALAsset *asset) {
18.
19. //add photo to the target album
20. [group addAsset: asset];
21.
22. //run the completion block
23. completionBlock(nil);
24.
25. } failureBlock: completionBlock];
26.
27. //album was found, bail out of the method
28. return;
29. }
30.
31. if (group==nil && albumWasFound==NO) {
32. //photo albums are over, target album does not exist, thus create it
33.
34. __weak ALAssetsLibrary* weakSelf = self;
35.
36. //create new assets album
37. [self addAssetsGroupAlbumWithName:albumName
38. resultBlock:^(ALAssetsGroup *group) {
39.
40. //get the photo's instance
41. [weakSelf assetForURL: assetURL
42. resultBlock:^(ALAsset *asset) {
43.
44. //add photo to the newly created album
45. [group addAsset: asset];
46.
47. //call the completion block
48. completionBlock(nil);
49.
50. } failureBlock: completionBlock];
51.
52. } failureBlock: completionBlock];
53.
54. //should be the last iteration anyway, but just in case
55. return;
56. }
57.
58. } failureBlock: completionBlock];
59. }
作者写了一个小demo：CustomAlbumDemo.zip 上面的代码用到了ARC，如果你的工程没有使用ARC，记得做相应处理。
如何添加分组：
1. [[DataCenter defaultAssetsLibrary] addAssetsGroupAlbumWithName:[alertView textFieldAtIndex:0].text
2. resultBlock:resulBlock
3. failureBlock:nil];
4.
