我有一个循环设置,下载一系列的图像,我以后将使用动画使用UI
ImageView的animationImages属性.我想知道我的循环中的所有块是否完成执行,所以我可以开始动画,并且想知道我可以在何时完成完成？谢谢！
for (PFObject *pictureObject in objects){
PFFile *imageFile = [pictureObject objectForKey:@"image"];
NSURL *imageFileURL = [[NSURL alloc] initWithString:imageFile.url];
NSURLRequest *imageRequest = [NSURLRequest requestWithURL:imageFileURL];
[tokenImageView setImageWithURLRequest:imageRequest placeholderImage:nil success:^(NSURLRequest *request,NSHTTPURLResponse *response,UIImage *image) {
[self.downloadedUIImages addObject:image]; //This is a mutableArray that will later be set to an UIImageView's animnationImages
} failure:^(NSURLRequest *request,NSError *error) {
NSLog(@"Error %@",error);
}];
}
//When I know all the blocks have finished downloading,I will then to animate the downloaded images.
编辑：问题与错误-999
在提供的答案中执行代码时遇到以下问题：Domain = NSURLErrorDomain Code = -999“无法完成操作(NSURLErrorDomain错误-999.)”
快速搜索reveals,错误-999表示“在上一个请求完成之前提出了另一个请求”…这是肯定的,因为我正在快速连接几个请求.建议的修正建议here对我来说不起作用,因为它只会成功下载一个UIImage(最后一个请求),以前的失败.我想知道有没有解决方法在这里或在AFNetworking我应该考虑？谢谢！
for (PFObject *pictureObject in objects){
PFFile *imageFile = [pictureObject objectForKey:@"image"];
NSURL *imageFileURL = [[NSURL alloc] initWithString:imageFile.url];
NSURLRequest *imageRequest = [NSURLRequest requestWithURL:imageFileURL];
AFHTTPRequestOperation *requestOperation = [[AFHTTPRequestOperation alloc] initWithRequest:imageRequest];
requestOperation.responseSerializer = [AFImageResponseSerializer serializer];
dispatch_group_enter(group);
[requestOperation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation,id responSEObject) {
NSLog(@"Response: %@",responSEObject);
UIImage *retrivedImage = (UIImage *)responSEObject;
[self.downloadedUIImages addObject:retrivedImage];
dispatch_group_leave(group);
} failure:^(AFHTTPRequestOperation *operation,NSError *error) {
NSLog(@"Image error: %@",error);
dispatch_group_leave(group);
}];
[requestOperation start];
counter ++;
}
dispatch_group_notify(group,dispatch_get_main_queue(),^{
NSLog(@"Horray everything has completed");
NSLog(@"What is here %@",self.downloadedUIImages);
NSLog(@"Done");
});
解决方法
创建一个调度组,在for循环中输入组,在完成块中离开组.然后可以使用dispatch_group_notify来查明所有块是否完成：
dispatch_group_t group = dispatch_group_create();
for (PFObject *pictureObject in objects){
PFFile *imageFile = [pictureObject objectForKey:@"image"];
NSURL *imageFileURL = [[NSURL alloc] initWithString:imageFile.url];
NSURLRequest *imageRequest = [NSURLRequest requestWithURL:imageFileURL];
dispatch_group_enter(group);
[tokenImageView setImageWithURLRequest:imageRequest placeholderImage:nil success:^(NSURLRequest *request,UIImage *image) {
[self.downloadedUIImages addObject:image]; //This is a mutableArray that will later be set to an UIImageView's animnationImages
dispatch_group_leave(group);
} failure:^(NSURLRequest *request,error);
dispatch_group_leave(group);
}];
}
dispatch_group_notify(group,^{
// do your completion stuff here
});
