如何运行 activity 指标直到下载图片完成

Question

我有一个 UITableView，每个 cell 都有一个图像。当我点击 cell 时，图像将被下载。我想显示 activity 指示器显示直到图像未下载。

这是代码

TableView代码

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
UITapGestureRecognizer *tap=[[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(PicturePerformGesture:)];
[cell.oMessageImg setUserInteractionEnabled:YES];
}

PicturePerformGesture代码

UIActivityIndicatorView  *iActivity=[[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
[iActivity startAnimating];
VideoData =[NSURLConnection sendSynchronousRequest:[NSURLRequest requestWithURL:videoUrl] returningResponse:nil error:nil];
[VideoData writeToFile:fullPath atomically:true];
 [iActivity stopAnimating];

下载前

正在下载

Answer 1

当您创建图像单元格时，您需要检查图像是否已下载，如果是，则可以点击图像，否则会在其上启动 ActivityIndicator，当您完成图像下载时，您可以停止 ActivityIndicator 以获得最佳图像下载体验使用SDWebImage 3rd 方库并获取所有图像状态，如下所述。

使用完成块：

// Here we use the new provided sd_setImageWithURL: method to load the web image
[cell.imageView sd_setImageWithURL:[NSURL URLWithString:@"http://www.example.com/path/to/image.jpg"]
                      placeholderImage:[UIImage imageNamed:@"placeholder.png"]
                             completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) {
                                ... completion code here ...

   // Add Your Stop Activity Code here.

}];

获取图像下载进度的另一种方法使用下面的代码块：

SDWebImageDownloader *downloader = [SDWebImageDownloader sharedDownloader];
[downloader downloadImageWithURL:imageURL
                         options:0
                        progress:^(NSInteger receivedSize, NSInteger expectedSize) {
                            // progression tracking code
                        }
                       completed:^(UIImage *image, NSData *data, NSError *error, BOOL finished) {
                            if (image && finished) {
                                // do something with image
                                // Assign Image to ImageView and stop activity Indicator View
                            }
                        }];

SDWebImage Link : https://github.com/rs/SDWebImage

或者您可以使用自己的代码在 GCD dispatch_async 的帮助下下载图像，如下所述。

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);
dispatch_async(queue, ^(void) {
                    //  You may want to cache this explicitly instead of reloading every time.
                    NSData *imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:[self.loader.parsedData[indexPath.row] objectForKey:@"imageLR"]]];
                    UIImage* image = [[UIImage alloc] initWithData:imageData];
                    dispatch_async(dispatch_get_main_queue(), ^{
                        // Capture the indexPath variable, not the cell variable, and use that
                        UITableViewCell *blockCell = [tableView cellForRowAtIndexPath:indexPath];
                        blockCell.imageView.image = image;
                        [blockCell setNeedsLayout];
                        //Stop Your ActivityIndicator View hare 
                    });
                });

希望对您有所帮助。

Answer 2

使用此方法在图像下载块代码之前开始动画。

[myActivityIndicator startAnimating];

并使用 iOS 这样的块在您的图像下载中停止它...

SDWebImageDownloader *downloader = [SDWebImageDownloader sharedDownloader];
[downloader downloadImageWithURL:imageURL
                     options:0
                    progress:^(NSInteger receivedSize, NSInteger expectedSize) {
                        // progression tracking code
                    }
                   completed:^(UIImage *image, NSData *data, NSError *error, BOOL finished) {
                        [myActivityIndicator startAnimating];
                        if (image && finished) {

                        }
                    }];

如何运行 activity 指标直到下载图片完成

How to run activity indicator till downloading the image is Complete

iphone

objective-c

nsdata

uiactivityindicatorview

ios