Obj-C检查照片库中是否已存在图像

在我的应用程序中,我必须实现保存图像功能。我已经做到了这样的储蓄:

  UIImage *image = [UIImage imageNamed:actualBackground];
  UIImageWriteToSavedPhotosAlbum(
      image, self,
      @selector(thisImage:hasBeenSavedInPhotoAlbumWithError:usingContextInfo:),
      nil);

/* ... */

- (void)thisImage:(UIImage *)image
    hasBeenSavedInPhotoAlbumWithError:(NSError *)error
                     usingContextInfo:(void *)ctxInfo {
  if (!error){
    UIImagePickerController *picker = [[UIImagePickerController alloc] init];
    [self presentViewController:picker animated:YES completion:nil];
  }
}

不幸的是,我必须检查文件是否已经存在,以防止冗余保存。这也是必要的,因为多次保存同一图像不会覆盖一个文件,但会创建其副本。。。

你知道如何解决那个问题吗?

解决方案:

根据 Shravya Boggarapu 回答我正在将assetUrl存储在 NSUserDefaults .完整代码:

- (IBAction)onDownloadClick:(UIButton *)sender {
  UIImage *image = [UIImage imageNamed:actualBackground];

  NSString *key = [NSString stringWithFormat:@"assetsUrl %@", actualBackground];
  NSString *savedValue =
      [[NSUserDefaults standardUserDefaults] stringForKey:key];
  NSURL *url = [NSURL URLWithString:savedValue];
  if (url != nil) {
    PHFetchResult *fetch =
        [PHAsset fetchAssetsWithALAssetURLs:[NSArray arrayWithObject:url]
                                    options:nil];
    if ([fetch count]) {
      UIAlertView *myAlert = [[UIAlertView alloc]
              initWithTitle:nil
                    message:NSLocalizedString(@"Already downloaded", nil)
                   delegate:self
          cancelButtonTitle:@"OK"
          otherButtonTitles:nil];
      [myAlert show];
      return;
    }
  }
  ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];

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

                     [library assetForURL:assetURL
                         resultBlock:^(ALAsset *asset) {
                           NSLog(@"assetURL %@", assetURL);
                           NSString *ass = [assetURL absoluteString];
                           [[NSUserDefaults standardUserDefaults]
                               setObject:ass
                                  forKey:key];
                           [[NSUserDefaults standardUserDefaults] synchronize];

                           UIAlertView *myAlert = [[UIAlertView alloc]
                                   initWithTitle:nil
                                         message:NSLocalizedString(
                                                     @"Image downloaded", nil)
                                        delegate:self
                               cancelButtonTitle:@"OK"
                               otherButtonTitles:nil];
                           [myAlert show];
                         }
                         failureBlock:^(NSError *error){
                         }];
                   }];
}

希望它能帮助一些人。