iphone - 从网络加载图像使应用程序挂起

Question

我正在我的 iPhone 应用程序中从网络加载图像。我将此图像用于表格单元格的 ImageView 。应用程序启动后几秒钟，所有图像都已完全加载。但表格的滚动不流畅。有延迟。滚动发生在手势后几秒钟。还有抽搐。我正在使用这段代码

UIImage *imagefromWeb = [UIImage imageWithData:[NSData dataWithContentsOfURL:[IconArray objectAtIndex:indexPath.row]]];
        CGSize newSize= CGSizeMake(45.0,45.0);
        UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);
        [imagefromWeb drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
        UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        cell.imageView.image=newImage;

Answer 1

您正在同步加载图片，这就是问题所在，请尝试使用以下代码异步下载图片:

        dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH,  0ul);
    dispatch_async(queue, ^{

        NSURL *imageURL=[NSURL URLWithString:urlString];
        NSData *imageData=[NSData dataWithContentsOfURL:imageURL];
        dispatch_sync(dispatch_get_main_queue(), ^{
            CustomCell *cell = (CustomCell *)[tableView cellForRowAtIndexPath:indexPath];
            cell.imageView.image=[UIImage imageWithData:imageData];
            [cell setNeedsLayout];

        });
    });