Question

我使用以下代码在我的ImageView中显示图像：

   imgbackBG.image = [UIImage imageWithData:
                   [NSData dataWithContentsOfURL:
                    [NSURL URLWithString:[NSString stringWithFormat:@"http://%@",    [test.arrImagessplash objectAtIndex:[test.arrImages count]-4]]]]];

    4cing.com/mobile_app/uploads/pageicon/splash.png

问题是代码执行速度非常慢。有没有办法加载图像并更快地在ImageView中显示它？如果是这样，我该怎么做？

Answer 1

您正在使用的代码在主线程上加载图像。这将阻止UI。使用GCD异步加载图像。

以下是示例代码：

dispatch_queue_t q = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);
        dispatch_async(q, ^{
            /* Fetch the image from the server... */
            NSData *data = [NSData dataWithContentsOfURL:url];
            UIImage *img = [[UIImage alloc] initWithData:data];
            dispatch_async(dispatch_get_main_queue(), ^{
                /* This is the main thread again, where we set the tableView's image to
                 be what we just fetched. */
                cell.imgview.image = img;
            });
        });

Answer 2

从这里下载文件.....

https://github.com/nicklockwood/AsyncImageView

并按以下方式使用：

AsyncImageView *asyncImageView = [[AsyncImageView alloc]initWithFrame:CGRectMake(30,32,100, 100)];   
[asyncImageView loadImageFromURL:[NSURL URLWithString:your url]];
[YourImageView addSubview:asyncImageView];
[asyncImageView release];

Answer 3

Best way to used `NSOperationQueue` to load Image in background.
Here is the sample code:


    NSOperationQueue *myQueue = [[NSOperationQueue alloc] init];
    [myQueue addOperationWithBlock:^{
        UIImage *img =  [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:@""]]]?:[UIImage imageNamed:@"defaultImage.png"];
        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
            YourImageView.image = img;

        }];
    }];

Answer 4

使用SdwebImage框架进行图像缓存

https://github.com/rs/SDWebImage

更快速地从URL加载图像并将其显示在iPhone应用程序中

4 个答案: