将图像保存到库时不显示HUD微调器

Question

您好，我正在实现一个“将图像保存到库”功能，如下面的代码片段所示。基本上，照片保存是在用户触摸页面上的图像时触发的。

TouchImageView *tiv = [[TouchImageView  alloc]initWithFrame:blockFrame];
        [tiv setCompletionHandler:^(NSString *imageUrl){
            //Spinner should start after user clicks on an image
            MBProgressHUD *hud = [MBProgressHUD showHUDAddedTo:self.navigationController.view animated:YES];
            hud.labelText = @"Saving photo to library";

            //trigger method to save image to library
            [self saveImageToLibrary];

        }];


-(void) saveImageToLibrary
{
    //convert url to uiimage
    UIImage *selectedImage = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:imageURL]]]; 

    //Save image to album
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];  
    // Request to save the image to camera roll  
    [library writeImageToSavedPhotosAlbum:[selectedImage CGImage] orientation:(ALAssetOrientation)[selectedImage imageOrientation] completionBlock:^(NSURL *assetURL, NSError *error){  

        [MBProgressHUD hideHUDForView:self.navigationController.view animated:YES];

        if (error) {  
            NSLog(@"error");  
        } else {  
            NSLog(@"url %@", assetURL);  
            //Trigger get photo from library function
            self.imgPicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
            [self presentModalViewController:self.imgPicker animated:YES];

        }  

    }];  
    [library release];     
}

问题是HUD微调器没有出现(在3-4秒的延迟时间之后)，我怀疑'writeImageToSavedPhotosAlbum:‘是同步的，并且锁定了进程，使其无法显示HUD微调器。是这样的吗？如何解决微调器显示中的滞后问题？

Answer 1

是的，这是正确的。替换呼叫

 [self saveImageToLibrary];

通过

[self performSelector:@selector(saveImageToLibrary) withObject:nil afterDelay:0];

这样HUD就有机会在你保存之前显示自己。