本来在下载完成之后，在UIImageWriteToSavedPhotosAlbum 里面响应
image: (UIImage *) image didFinishSavingWithError: (NSError *) error contextInfo: (void *) contextInfo
这个函数，然后来更新UI的，但是操作比较繁琐，而且UI的更新总是无法同步。所以采用GCD的方式，来完成，非常顺畅。
- (void)downloadImageToPhotoAlbum
{
[self.viewaddSubview:downloadingView];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSURL *photoUrl = [NSURL URLWithString:self.photoVersionLargerUrl];
NSData *photoData = [NSData dataWithContentsOfURL:photoUrl];
UIImageWriteToSavedPhotosAlbum([UIImageimageWithData:photoData], nil, nil, nil);
dispatch_async(dispatch_get_main_queue(), ^{
[downloadingViewremoveFromSuperview];
});
});
}
- (void)processImage:(UIImage *)image
{
[image retain];
UIImageWriteToSavedPhotosAlbum(image, self, @selector(image:didFinishSavingWithError:contextInfo:), nil);
}
- (void) image: (UIImage *) image
didFinishSavingWithError: (NSError *) error
contextInfo: (void *) contextInfo
{
// [downloadingView removeFromSuperview];
NSLog(@"Save image complete!");
if(error != nil) {
NSLog(@"Error when saving image :%@",[error localizedDescription]);
}
// [image autorelease];
}