如何在应用程序中将图像保存在本地

Question

嗨，我正在开发一个基于聊天的应用程序，现在我想在本地保存图像，因为我已经使用以下代码在本地设备中创建了一个目录"My_Videos"。

 NSString *albumName=@"My_Videos";
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
[library addAssetsGroupAlbumWithName:albumName
                         resultBlock:^(ALAssetsGroup *group) {
                             NSLog(@"added album:%@", albumName);
                         }
                        failureBlock:^(NSError *error) {
                            NSLog(@"error adding album");
                        }];

正在成功创建文件夹但是现在我想从 Web API 下载图像并保存在我在设备中创建的 "My_Videos" 文件夹中。请帮帮我。

Answer 1

您在 AssetsLibrary 中创建新组的方向是正确的。以下是如何在此处添加照片：

首先您需要将照片写入标准资产库（相机胶卷）

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

[library writeImageToSavedPhotosAlbum:image.CGImage
                          orientation:(ALAssetOrientation)image.imageOrientation
                      completionBlock:^(NSURL* assetURL, NSError* error)
 {
     if (!error) {

         __block BOOL albumAlredyCreated = NO;

         // Check if Album already exists
         [library enumerateGroupsWithTypes:ALAssetsGroupAlbum
                                usingBlock:^(ALAssetsGroup *group, BOOL *stop)
          {
              if ([customAlbum compare: [group valueForProperty:ALAssetsGroupPropertyName]]==NSOrderedSame)
              {
                  albumAlredyCreated = YES;

                  //Get the ALAsset instance for the saved image
                  [library assetForURL: assetURL
                           resultBlock:^(ALAsset *asset)
                   {

                       //Save photo to customAlbum
                       [group addAsset: asset];

                   } failureBlock:^(NSError *error) {

                       // If the user denies access to the application or if no application is allowed to access the data, the failure block will be called.
                       // If the data is currently unavailable, the failure block will be called.
                   }];
              }

              // Album does not exist. Create it
              if (group == nil && albumAlredyCreated == NO)
              {
                  __weak ALAssetsLibrary* weakLibrary = library;

                  [library addAssetsGroupAlbumWithName:customAlbum
                                           resultBlock:^(ALAssetsGroup *group)
                   {

                       //Get the ALAsset instance for the saved image
                       [weakLibrary assetForURL: assetURL
                                    resultBlock:^(ALAsset *asset) {

                                        //Save photo to customAlbum
                                        [group addAsset: asset];

                                    } failureBlock:^(NSError *error) {

                                        // If the user denies access to the application or if no application is allowed to access the data, the failure block will be called.
                                        // If the data is currently unavailable, the failure block will be called.
                                    }];
                   } failureBlock:^(NSError *error) {

                       // If the user denies access to the application or if no application is allowed to access the data, the failure block will be called.
                   }];
              }

          } failureBlock:^(NSError *error) {

              // If the user denies access to the application, or if no application is allowed to access the data, the failureBlock is called.
          }];
     }
 }];

虽然这可行，但 ALAssetsLibrary 在 iOS 9 中被删除，因此您可能需要考虑移动到 PHPhotoLibrary。

NS_CLASS_DEPRECATED_IOS(4_0, 9_0, "Use PHPhotoLibrary from the Photos framework instead") @interface ALAssetsLibrary : NSObject

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