异步图像下载器 [英] Async image downloader

问题描述

我已经写了一个小类来通过使用NSURLConnection执行图像的下载。
这个想法是将下载委托给这个类，以避免阻止执行。

所以我将目标UIImageView（由ref）和url传递给函数并开始下载：

   - （void）getImage：（UIImageView **）image formUrl：（NSString *）urlStr 
 {
 NSLog（@Downloader.getImage.url.debug：％@，urlStr）; 
 NSURL * url = [NSURL URLWithString：urlStr]; 
 NSURLRequest * req = [NSURLRequest requestWithURL：url cachePolicy：NSURLRequestReturnCacheDataElseLoad timeoutInterval：5.0]; 
 [[UIApplication sharedApplication] setNetworkActivityIndi​​catorVisible：YES]; 
 NSURLConnection * c = [[NSURLConnection alloc] initWithRequest：req delegate：self]; 
 [conn addObject：c]; 
 int i = [conn indexOfObject：c]; 
 [imgs insertObject：* image atIndex：i]; 
 [c release]; 
} 
  

完成设置图像并更新imageView：

   - （void）connectionDidFinishLoading :( NSURLConnection *）连接
 {
 int i = [conn indexOfObject：connection]; 
 
 NSData * rawData = [buffer objectAtIndex：i]; 
 UIImage * img = [UIImage imageWithData：rawData]; 
 UIImageView * imgView = [imgs objectAtIndex：i]; 
 imgView.image = img; 
 
 [imgView setNeedsDisplay]; 
 
 [conn removeObjectAtIndex：i]; 
 [imgs removeObjectAtIndex：i]; 
 [buffer removeObjectAtIndex：i]; 
 
 if（[conn count] == 0）{
 [[UIApplication sharedApplication] setNetworkActivityIndi​​catorVisible：NO]; 
} 
} 
  

这个系统工作得很好，但我不能在UITableViewCell的单元格中更新UIImageView，任何想法？ （实际上，当我点击它更新的单元格）
有更好的方法来实现这个功能？ （实际上需要的是：非阻塞，缓存系统）

解决方案

Cesar

对于异步图像加载，缓存和线程操作，我使用来自 http://github.com/的SDImageCache类RS / SDWebImage 。我也写了我自己的几次，但这一个是辉煌的，我抛出了我所有的旧代码。

从它的文档：

只需 #import UIImageView + WebCache.h 标题，并从 tableView：cellForRowAtIndexPath： UITableViewDataSource方法中调用 setImageWithURL：placeholderImage：方法。一切都将为您处理，从异步下载到缓存管理。

希尔顿

I have write a little class to perform the download of the images by using an NSURLConnection. The idea it's to delegate the download to this class to avoid to block the execution.

So I pass the target UIImageView (by ref) and the url to the function and start the download:

-(void)getImage:(UIImageView**)image formUrl:(NSString*)urlStr
{
    NSLog(@"Downloader.getImage.url.debug: %@",urlStr);
    NSURL *url = [NSURL URLWithString:urlStr];
    NSURLRequest *req = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReturnCacheDataElseLoad timeoutInterval:5.0];
    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
    NSURLConnection *c = [[NSURLConnection alloc] initWithRequest:req delegate:self];
    [conn addObject:c];
    int i = [conn indexOfObject:c];
    [imgs insertObject:*image atIndex:i];
    [c release];
}

When it's finished set the image and update the imageView:

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    int i = [conn indexOfObject:connection];

    NSData *rawData = [buffer objectAtIndex:i];
    UIImage *img = [UIImage imageWithData:rawData];
    UIImageView *imgView = [imgs objectAtIndex:i];
    imgView.image = img;

    [imgView setNeedsDisplay];

    [conn removeObjectAtIndex:i];
    [imgs removeObjectAtIndex:i];
    [buffer removeObjectAtIndex:i];

    if ([conn count]==0) {
        [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
    }
}

This system works quite good, but i can't get updated the UIImageView inside the cells of a UITableViewCell, any idea ? (actually the cell it's updated when I click on it) There is a better way to implement this functionality ? (actually the need are: non-blocking, caching system)

解决方案

Cesar

For async image loading, caching and threaded operation, I use SDImageCache class from http://github.com/rs/SDWebImage. I also wrote my own several times, but this one is brilliant and I've thrown all my old code away.

From its documentation:

Just #import the UIImageView+WebCache.h header, and call the setImageWithURL:placeholderImage: method from the tableView:cellForRowAtIndexPath: UITableViewDataSource method. Everything will be handled for you, from async downloads to caching management.

Hilton

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