我正在尝试实现 UICollectionView 并显示图像。我正在使用 SDWebimage，它在 tableviewcells 中完美运行，但是当我尝试在 UICollectionviewCell 中使用它时，它不会停止并删除 activityindicator。如果没有下载的图像，它会放置占位符图像。我不确定可能导致此问题的 tableviewcell 和 collectionviewcell 之间的区别是什么。

代码如下:

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"personImageCell";

    PersonCollectionViewCell *cell = (PersonCollectionViewCell *)[collectionView dequeueReusableCellWithReuseIdentifier:CellIdentifier forIndexPath:indexPath];
    Person *person = [self.fetchedResultsController objectAtIndexPath:indexPath];
    NSString *imgURL=[person.imageurl stringByAppendingString:@"?maxheight=300&maxwidth=400"];

    UIActivityIndicatorView *activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
    activityIndicator.hidesWhenStopped = YES;
    activityIndicator.hidden = NO;
    [activityIndicator startAnimating];
    activityIndicator.center = CGPointMake(cell.ivPersonImage.frame.size.width /2, cell.ivPersonImage.frame.size.height/2);
    [cell.ivPersonImage setImageWithURL:[NSURL URLWithString:imgURL] placeholderImage:nil options:SDWebImageProgressiveDownload success:^(UIImage *image, BOOL cached){
        [activityIndicator stopAnimating];[activityIndicator removeFromSuperview];
        NSLog(@"activity indicator should be removed");
    }failure:^(NSError *error){
        [activityIndicator stopAnimating];[activityIndicator removeFromSuperview];
        cell.ivPersonImage.image = [UIImage imageNamed:@"placeholder.png"];
    }];


    [cell.ivPersonImage addSubview:activityIndicator];
    return cell;
}

更新:

当我执行 NSLog(@"activity indicator should be removed %@,activityIndi​​cator);

我得到这个输出:

 activity indicator should be removed <UIActivityIndicatorView: 0xa520ab0; frame = (65 90; 20 20); hidden = YES; layer = <CALayer: 0xa520b60>> 

它显示 UIActivityindicator 已隐藏，但它仍显示在图像顶部

最佳答案

看来您正在重用单元格，所以有不止一个 UIActivityIndi​​catorView。

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"personImageCell";

    PersonCollectionViewCell *cell = (PersonCollectionViewCell *)[collectionView dequeueReusableCellWithReuseIdentifier:CellIdentifier forIndexPath:indexPath];
    Person *person = [self.fetchedResultsController objectAtIndexPath:indexPath];
    NSString *imgURL=[person.imageurl stringByAppendingString:@"?maxheight=300&maxwidth=400"];

    UIActivityIndicatorView *activityIndicator = [cell.ivPersonImage viewWithTag:10];
    if (activityIndicator) [activityIndicator removeFromSuperview];
    activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
    activityIndicator.hidesWhenStopped = YES;
    activityIndicator.hidden = NO;
    [activityIndicator startAnimating];
    activityIndicator.center = cell.ivPersonImage.center;
    activityIndicator.tag = 10;

    [cell.ivPersonImage addSubview:activityIndicator];
    [cell.ivPersonImage setImageWithURL:[NSURL URLWithString:imgURL] placeholderImage:nil options:SDWebImageProgressiveDownload success:^(UIImage *image, BOOL cached){
        [activityIndicator stopAnimating];[activityIndicator removeFromSuperview];
        NSLog(@"activity indicator should be removed");
    }failure:^(NSError *error){
        [activityIndicator stopAnimating];[activityIndicator removeFromSuperview];
        cell.ivPersonImage.image = [UIImage imageNamed:@"placeholder.png"];
    }];

    return cell;
}

关于objective-c - ActivityIndi​​cator 不会停止动画，也不会从 UICollectionViewCell 的 super View 中删除，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/12868270/