xcode uicollectionview 中的延迟加载
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Lazy loading in uicollectionview
提问by Vix Hunk
here is the code for my collectionview it is showing records but loading really please tell me how can i implement lazy loading on this i also have a placeholder pic in my project
这是我的 collectionview 的代码，它显示记录，但加载真的请告诉我如何实现延迟加载我的项目中还有一个占位符图片
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
CollectionViewCell* cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"MJCell" forIndexPath:indexPath];
// Setup image name
NSString *url = [[rssOutputData objectAtIndex:indexPath.row]xmllink];
UIImage *img = nil;
NSData *data = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:url]];
img = [[UIImage alloc] initWithData:data];
cell.MJImageView.image = img;
return cell;
}
right now it is working but very very slow.
现在它正在工作，但非常非常慢。
回答by Amit
It's pretty easy to do lazy loading using GCD.
使用 GCD 进行延迟加载非常容易。
// Create a queue for the operations
dispatch_queue_t queue = dispatch_queue_create("photoList", NULL);
// Start getting the data in the background
dispatch_async(queue, ^{
NSData* photoData = [NSData dataWithContentsOfURL:[NSURL URLWithString:object.photoURL]];
UIImage* image = [UIImage imageWithData:photoData];
// Once we get the data, update the UI on the main thread
dispatch_sync(dispatch_get_main_queue(), ^{
cell.photoImageView.image = image;
});
});
回答by Azat
The easiest way to implement that is use SDWebImagelibrary, it does right what you need. There is UIImageViewcategory that will allow you to modify code for that:
实现它的最简单方法是使用SDWebImage库，它可以满足您的需求。有一个UIImageView类别可以让您修改代码：
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
CollectionViewCell* cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"MJCell" forIndexPath:indexPath];
// Setup image name
NSString *url = [[rssOutputData objectAtIndex:indexPath.row]xmllink];
[cell.MJImageView sd_setImageWithURL:[NSURL URLWithString:url]];
return cell;
}
回答by iShaalan
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString: @"url.com"]];
UIActivityIndicatorView * indicator = [[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
[yourImageView addSubview:indicator];
indicator.center = yourImageView.center;
[indicator startAnimating];
[yourImageView setImageWithURLRequest:request
placeholderImage:[UIImage imageNamed:@"placeholder.png"]
success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
dispatch_async(dispatch_get_main_queue(), ^(void){
yourImageView.image = image;
});
[indicator stopAnimating];
[indicator removeFromSuperview];
} failure:nil];
回答by Mr Phuc 87
Maybe, because your image is so large You can use NSThread for loading
也许，因为你的图片太大了 你可以使用 NSThread 进行加载
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
CollectionViewCell* cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"MJCell" forIndexPath:indexPath];
cell.tag = indexPath.row; //For index
[NSThread detachNewThreadSelector:@selector(loadImage:) toTarget:self withObject:cell];
return cell;
}
- (void) loadImage:(CollectionViewCell *)cell {
NSString *url = [[rssOutputData objectAtIndex:cell.tag]xmllink];
UIImage *img = nil;
NSData *data = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:url]];
img = [[UIImage alloc] initWithData:data];
cell.MJImageView.image = img;
}
