如何在应用程序中将图像保存在本地

Question

嗨，我现在正在开发一个基于聊天的应用程序，我想在本地保存图像，为此我使用以下代码在设备本地创建了一个目录"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");
                        }];

它已成功创建文件夹，但现在我想从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 中创建新组是正确的。以下是在那里添加照片的方法：

首先，您需要将照片写入标准资源库（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.
          }];
     }
 }];

虽然这可以工作，但ALAssetsLibrary在iOS 9中已弃用，因此您可能需要考虑迁移到 PHPhotoLibrary 。

NS_CLASS_DEPRECATED_IOS（4_0， 9_0， "使用 PHPhotoLibrary from the Photos 框架代替"） @interface ALAssetsLibrary ： NSObject