如何使用objective-c将图像存储在缓存中

Question

I am having problem when multiple images are being displayed in scrollview (photo Gallery). I have fetched images from document directory. when I display more then 100 images application is getting crashed . so I want to store images in cache memory.

I want to display first 15 images and then other from cache memory. when I scroll the scrollview first 15 from cache will be displayed and then next will be displayed.

The requirement is to display images in scrollview not in collectionView or other component.

files is array of image paths fetched from documents directory.

I have fetched all images path and stored in files array .

int x=2,y=5;
for (int i = 0; i < files.count ; i++)
 {
   if(x<=308)
    {
       NSString *setPath=[NSString stringWithFormat:@"%@/%@",filePath,[files objectAtIndex:i]];
       UIImage* imagePath = [UIImage imageWithContentsOfFile:setPath];
       imgView=[[UIImageView alloc]initWithFrame:CGRectMake(x, y, 77, 75)];
       imgView.image=imagePath; 
       x+=80;
    }
    else
    {
        x=2;
        y+=77;

        NSString *setPath=[NSString stringWithFormat:@"%@/%@",filePath,[files objectAtIndex:i]];
        UIImage* imagePath = [UIImage imageWithContentsOfFile:setPath];
        imgView=[[UIImageView alloc]initWithFrame:CGRectMake(x, y, 77, 75)];
        imgView.image=imagePath;
        x+=80;
    }
        [gallaryScrollView addSubview:imgView];
        [self.view addSubview:gallaryScrollView];
         gallaryScrollView.contentSize=CGSizeMake(320, y+120);
 }

Answer 1

Caching isn't going to solve your memory problem. (If anything, using additional memory cache only places more memory strain on the app.) You use cache for performance reasons, not for reducing memory usage.

The issue is that you're attempting to load image views into scroll view up front. I'd suggest doing lazy loading of the image views and their associated images. And rather than doing it in batches of 15 (or whatever), I'd suggest doing it dynamically in your UIScrollViewDelegate methods:

• setting delegate for your scroll view;

• implement scrollViewDidScroll which will:

  • remove any image views from the scroll view that are not visible (or near, at the very least)

  • add any image views that have scrolled into view and set its image property

If you want to marry this with NSCache for caching for performance reasons, you can do that if you want, but I'd suggest focusing on the main manual scroll view delegate implementation first.