目标 - C:从 URL 加载图像?

织梦狗教程移动开发问题

2022-01-01

objective - C : Loading image from URL?(目标 - C:从 URL 加载图像?)

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问题描述

Sorry for question title. I can not find a suitable title.

I have UITableView content images from url when i open the UITableView the View did not show until the images loaded and that takes along time.

I get the images from JSON by php.

I want to show the table and then images loading process.

This is code from my app:

NSDictionary *info = [json objectAtIndex:indexPath.row];
cell.lbl.text = [info objectForKey:@"title"];
NSString *imageUrl = [info objectForKey:@"image"];
cell.img.image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:imageUrl]]];
[cell.img.layer setBorderColor: [[UIColor blackColor] CGColor]];
[cell.img.layer setBorderWidth: 1.0];

return cell;

Sorry my english is weak.

解决方案

Perform the web request on a separate thread, to not block the UI. Here is an example using NSOperation. Remember to only update the UI on the main thread, as shown with performSelectorOnMainThread:.

- (void)loadImage:(NSURL *)imageURL
{
    NSOperationQueue *queue = [NSOperationQueue new];
    NSInvocationOperation *operation = [[NSInvocationOperation alloc]
                                        initWithTarget:self
                                        selector:@selector(requestRemoteImage:)
                                        object:imageURL];
    [queue addOperation:operation];
}

- (void)requestRemoteImage:(NSURL *)imageURL
{
    NSData *imageData = [[NSData alloc] initWithContentsOfURL:imageURL];
    UIImage *image = [[UIImage alloc] initWithData:imageData];

    [self performSelectorOnMainThread:@selector(placeImageInUI:) withObject:image waitUntilDone:YES];
}

- (void)placeImageInUI:(UIImage *)image
{
    [_image setImage:image];
}

这篇关于目标 - C:从 URL 加载图像?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持编程学习网！

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