如何從後臺加載許多照片url（異步）

我有這種方法我用來加載許多圖像滾動視圖，但是當圖像加載從url我的滾動視圖卡住，我不明白如何加載他們在後臺，所以用戶不會感覺到它。如何從後臺加載許多照片url（異步）

該方法將在「for」循環中調用幾次（8）。

- (void)loadPhotosToLeftscroll{ 

    //getting image information from JSON 
    NSMutableDictionary *photoDict; 
    photoDict = [leftPhotoArray lastObject]; 

    //getting the photo 
    NSString *photoPath = [photoDict objectForKey:@"photos_path"]; 
    NSLog(@"photo Path:%@",photoPath); 


    NSData * imageData = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:photoPath]];  

      UIImage *image = [UIImage imageWithData:imageData]; 
      // use the image how you like, say, as your button background 

      //calculating the hight of next photo 
      UIImageView *leftImage = [leftBlockScroll.subviews lastObject]; 

      //allocating photoView 
      UIImageView *photoView = [[UIImageView alloc]initWithFrame:CGRectMake(5 , leftImage.frame.origin.y + leftImage.frame.size.height+5, image.size.width/2, image.size.height/2)]; 
      photoView.userInteractionEnabled=YES; 
      [photoView.layer setMasksToBounds:YES]; 
      [photoView.layer setCornerRadius:3]; 


      //getting items list 
      NSDictionary *sh_items = [photoDict objectForKey:@"items"]; 

      //adding image button 
      UIButton *imageOverButton = [UIButton buttonWithType:UIButtonTypeCustom]; 
      imageOverButton.frame = CGRectMake(0, 0, photoView.frame.size.width, photoView.frame.size.height); 
      [imageOverButton addTarget:self action:@selector(LeftimagePressed:) forControlEvents:UIControlEventTouchUpInside]; 
      [imageOverButton setTag:[leftPhotoArray count]-1]; 
      [photoView addSubview:imageOverButton]; 

      //adding sh button to imageView 
      [self addThe_sh_signs:sh_items To_ImageView:photoView]; 

      //subViewing the image to the scrollView 
      [self insert_Image:image toImageView:photoView in_Scroll:leftBlockScroll]; 

      //calclulating the position of next imageView in scroll. 
      nextLeftPhotoHight = photoView.frame.size.height + photoView.frame.origin.y + 5; 

      //calculating the hight of the highest scroll view in both. 
      leftBlockScroll.contentSize = CGSizeMake(160, [self theSizeOfScrollViewHight]); 
      rightBlocScroll.contentSize = CGSizeMake(160, [self theSizeOfScrollViewHight]); 
      isLoadindContant = NO; 
      [self.view reloadInputViews]; 
      [leftBlockScroll reloadInputViews]; 

}

請不要給我發一些鏈接，試圖解釋如何使用異步的。嘗試按照您在此處看到的方法進行解釋。 我在這裏的任何問題，你需要問我來幫助我。

來源

2012-06-27 Amir Foghel

我很確定你這樣做的方式解釋「前景」加載。 – Dustin