如何学习新的框架(保存图片到相册)

 1 - (void)viewDidLoad {
 2     [super viewDidLoad];
 3    
 4     UIImage *image = [[SDImageCache sharedImageCache] imageFromDiskCacheForKey:_item.image0];
 5    
 6     UIImageView *imageView = [[UIImageView alloc] init];
 7     _imageView = imageView;
 8     [imageView sd_setImageWithURL:[NSURL URLWithString:_item.image1] placeholderImage:image];
 9     CGFloat h = XMGScreenW / _item.width * _item.height;
10     imageView.frame = CGRectMake(0, 0, XMGScreenW, h);
11     [_scroolView addSubview:imageView];
12    
13     if (_item.is_bigPicture) {
14         _scroolView.contentSize = CGSizeMake(0, h);
15        
16         if (_item.height > h) {
17             CGFloat scale = _item.height / h;
18           //2.设置缩放比例
19             _scroolView.maximumZoomScale = scale;
20             _scroolView.minimumZoomScale = 1; 
21         }
22     } else {
23         imageView.center = CGPointMake(XMGScreenW * 0.5, XMGScreenH * 0.5);
24     }
25     // 缩放
26         //1.设置代理,告诉它哪个View需要做缩放
27         //2.设置缩放比例
28     _scroolView.delegate = self;
29 }
30 #pragma mark - UIScrollViewDelegate
31 // 作用:返回需要做缩放的view
32 // 调用:每次缩放的时候才会调用
33 - (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
34 {
35     return _imageView;
36 }

 1 // 点击保存调用
 2 - (IBAction)save:(id)sender {
 3     // 保存系统相册
 4     UIImageWriteToSavedPhotosAlbum(_imageView.image, self, @selector(image:didFinishSavingWithError:contextInfo:), nil);
 5 }
 6 // 询问下用户是否允许当前app访问相册
 7 // 监听图片是否保存完成
 8 - (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo
 9 {
10     if (error) {
11         [SVProgressHUD showErrorWithStatus:@"保存失败"];
12     } else {
13         [SVProgressHUD showSuccessWithStatus:@"保存成功"];
14     }
15 }

 1 // 点击保存调用
 2 - (IBAction)save:(id)sender {
 3    //查看当前app授权状态
 4     PHAuthorizationStatus status = [PHPhotoLibrary authorizationStatus];
 5     switch (status) {
 6         case PHAuthorizationStatusNotDetermined:
 7         { // 未授权,弹出授权框
 8             [PHPhotoLibrary requestAuthorization:^(PHAuthorizationStatus status) {
 9                // 用户选择完毕就会调用—选择允许,直接保存
10                 if (status == PHAuthorizationStatusAuthorized) {
11                     [self savePhoto];
12                 }
13             }];
14            选择不允许访问,就不保存
15             break;
16         }
17         case PHAuthorizationStatusAuthorized:
18         { // 授权,就直接保存
19             [self savePhoto];
20             break;
21         }
22         default:
23         {// 拒绝   告知用户去哪打开授权
24             [SVProgressHUD showInfoWithStatus:@"打开设置 -> 查找百思不得姐 -> 打开照片开关 -> 允许当前app访问系统相册就可以保存图片"];
25             break;
26         }
27     }
28 }
29 
30 // 添加图片到自己相册
31 - (void)savePhoto
32 {
33     [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
34         // 1.创建图片请求类(创建系统相册中新的图片)PHAssetCreationRequest
35         // 把图片放在系统相册
36         PHAssetCreationRequest *assetCreationRequest = [PHAssetCreationRequest creationRequestForAssetFromImage:_imageView.image];
37        
38         // 2.创建相册请求类(修改相册)PHAssetCollectionChangeRequest
39         PHAssetCollectionChangeRequest *assetCollectionChangeRequest = nil;
40        
41         // 获取之前相册
42         PHAssetCollection *assetCollection = [self fetchAssetCollection:@"百思不得姐"];
43        
44         // 判断是否已有相册
45         if (assetCollection) {
46             // 如果存在已有同名相册   指定这个相册,创建相册请求修改类  
47             assetCollectionChangeRequest = [PHAssetCollectionChangeRequest changeRequestForAssetCollection:assetCollection];
48         } else {  //不存在,创建新的相册
49             assetCollectionChangeRequest = [PHAssetCollectionChangeRequest creationRequestForAssetCollectionWithTitle:@"百思不得姐"];
50         } 
51         // 3.把图片添加到相册中
52         // NSFastEnumeration:以后只要看到这个,就可以表示数组
53         //assetCreationRequest.placeholderForCreatedAsset 图片请求类占位符(相当于一个内存地址) 
54          //因为creationRequestForAssetFromImage方法是异步实行的,在这里不能保证 assetCreationRequest有值
55  
56         [assetCollectionChangeRequest addAssets:@[assetCreationRequest.placeholderForCreatedAsset]];
57  
58     } completionHandler:^(BOOL success, NSError * _Nullable error) {
59        
60         if (success) {
61             [SVProgressHUD showSuccessWithStatus:@"保存成功"];
62         } else {
63             [SVProgressHUD showErrorWithStatus:@"保存失败"];
64         }
65        
66     }];
67 }
68 
69 // 指定相册名称,获取相册
70 - (PHAssetCollection *)fetchAssetCollection:(NSString *)title
71 {
72     // 获取相簿中所有自定义相册
73     PHFetchResult *result = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeAlbum subtype:PHAssetCollectionSubtypeAlbumRegular options:nil];
74     遍历相册,判断是否存在同名的相册
75     for (PHAssetCollection *assetCollection in result) {
76         if ([title isEqualToString:assetCollection.localizedTitle]) {  存在,就返回这个相册
77             return assetCollection;
78         }
79     }  
80     return nil;
81 }