iphone - 停止从新线程加载照片

Question

我正在使用此类加载图像。我需要有关如何在调用 dealloc 时阻止它们加载的帮助。该类扩展了 UIImageView。另外，对于设计类的任何其他建议，我都会表示赞赏，例如，我希望分派(dispatch)加载的字节。

@implementation RCPhoto

- (id)initWithFrame:(CGRect)frame delegate:(id)d {
    if ((self = [super initWithFrame:frame])) {
        // Initialization code
        delegate = d;
        self.contentMode = UIViewContentModeScaleAspectFit;
    }
    return self;
}

- (void)dealloc {
    [super dealloc];

}

#pragma mark Load photo
- (void)loadImage:(NSString *)path {
    // Create a new thread for loading the image
    [NSThread detachNewThreadSelector:@selector(load:) 
                             toTarget:self 
                           withObject:path];
}

- (void)load:(NSString *)path {

    // You must create a autorelease pool for all secondary threads.
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

    //NSLog(@"RCPhoto loadImage into a new thread: %@", path);
    NSURL *url = [NSURL URLWithString: path];
    NSData *data = [NSData dataWithContentsOfURL: url];
    UIImage *image = [[UIImage alloc] initWithData: data];

    [self performSelectorOnMainThread: @selector(performCompleteEvent:)
                           withObject: image
                        waitUntilDone: NO];

    [pool release];
}

- (void)performCompleteEvent:(UIImage *)image {
    //NSLog(@"RCPhoto finish loading");

    [self setImage:image];
    self.opaque = YES;

    if ([delegate respondsToSelector:@selector(onPhotoComplete)]) {
        [delegate performSelector:@selector(onPhotoComplete)];
    }
}


@end

Answer 1

dataWithContentsOfURL: 被设计为阻塞，直到超时或完成接收完整响应。您似乎有兴趣在解除分配关联 View 时中断后台线程。这些事实从根本上来说是不一致的。

如果您想在对象消失时尽快终止请求，可以通过使用 NSURLConnection 发出异步请求并取消来完成在您的 dealloc 方法中。如果在收到响应之前没有取消，您将在委托(delegate)上收到对 connectionDidFinishLoading: 的回调，此时您可以根据收到的响应重新构建 UIImage数据。