UIImageView需要时间来加载图像

我有一些问题，我想从特定链接从互联网上下载图像下载此图像发生在其他类，这是singlton类名称更多AppInternet.m

我的moreAppInterNet.m文件如下

// finishedImgDling是bool

// mutableData是NSMutableData

// urlConnection是NSURLConnection

// appimage是UIImage

// imageUrl是包含链接的NSString

（id）sharedManager {

static moreAppInterNet *sharedMyManager = nil;

@synchronized(self) {

    if (sharedMyManager == nil)

        sharedMyManager = [[self alloc] init];
}

return sharedMyManager;

}

• （void）downloadImageFromUrl {
  finishedImgDling = NO;

[self.mutableData setLength:0];

self.urlConnection = [NSURLConnection connectionWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:self.imageUrl]] delegate:self];


while(!finishedImgDling) {
    [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
}

}

• （void）connection：（NSURLConnection *）connection didReceiveResponse：（NSURLResponse *）response {

if (connection == self.urlConnection)
{

    NSLog(@"imageDling");
}

}

• （void）connection：（NSURLConnection *）connection didReceiveData：（NSData *）data {

if (connection == self.urlConnection)
{

    if (self.mutableData == nil)
    {
        self.mutableData = [NSMutableData data];
    }

    [self.mutableData appendData:data];
}

}

• （void）connectionDidFinishLoading：（NSURLConnection *）connection {

if (connection == self.urlConnection)
{
    NSLog(@"image Downloaded");

    finishedImgDling = YES;

    [self setUrlConnection:nil];

    [self storeImage];
}

}

• （void）storeImage {

[self setAppimage:nil];

self.appimage = [UIImage imageWithData:self.mutableData];

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];     
NSFileManager *fileManager = [NSFileManager defaultManager];

NSString *path =[documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"appImage.png"]];

[fileManager createFileAtPath:path contents:UIImagePNGRepresentation(self.appimage) attributes:nil];

 NSLog(@"downloading and storing complete");

}

我的另一个ViewController如下所示，我调用该函数

• （void）viewDidLoad {

[moreAppInterNet sharedManager];

[self downloadImage];

}

• （void）downloadImage {

NSInvocationOperation *operation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(download_Image_from_other_class) object:nil];

NSOperationQueue *que = [[NSOperationQueue alloc] init];

[que addObserver:self forKeyPath:@"operations" options:0 context:NULL];

[que addOperation:operation];

[operation release];

self.dlingQue = que;

[que release];

}

• （void）download_Image_from_other_class {

[[moreAppInterNet sharedManager] downloadImageFromUrl];

}

• （void）observeValueForKeyPath：（NSString *）keyPath ofObject：（id）object change：（NSDictionary *）change context：（void *）context {

if ([keyPath isEqualToString:@"operations"] && object == self.dlingQue)
{

    if ([self.dlingQue operationCount] == 0)
    {

        self.imgView = [[moreAppInterNet sharedManager] appimage];

        //it takes lots of time to display image in UIImageView
        //Even though Above line get executed
    }
}
else {

    [super observeValueForKeyPath:keyPath ofObject:object
                           change:change context:context];
}

}

问题是self.imgView需要很多时间来加载图像大约5秒，即使它完全下载

任何人都可以帮助我或告诉我我做错了什么