使用url设置UIImageView图像

Question

是否可以读取图像的URL并将UIImageView设置为此URL的图像？

Answer 1

NSString *ImageURL = @"YourURLHere";
NSData *imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:ImageURL]];
imageView.image = [UIImage imageWithData:imageData];

Answer 2

对于这样一个简单的任务,我强烈建议不要集成像Three20这样的项目,这个库是一个怪物而且不是很容易起床和运行.

我会推荐这种方法:

NSString *imageUrl = @"http://www.foo.com/myImage.jpg";
[NSURLConnection sendAsynchronousRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:imageUrl]] queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
    myImageView.image = [UIImage imageWithData:data];
}];

编辑Swift 3.0

let urlString = "http://www.foo.com/myImage.jpg"
guard let url = URL(string: urlString) else { return }
URLSession.shared.dataTask(with: url) { (data, response, error) in
    if error != nil {
        print("Failed fetching image:", error)
        return
    }

    guard let response = response as? HTTPURLResponse, response.statusCode == 200 else {
        print("Not a proper HTTPURLResponse or statusCode")
        return
    }

    DispatchQueue.main.async {
        self.myImageView.image = UIImage(data: data!)
    }
}.resume()

*编辑Swift 2.0

let request = NSURLRequest(URL: NSURL(string: urlString)!)

NSURLSession.sharedSession().dataTaskWithRequest(request) { (data, response, error) -> Void in

    if error != nil {
        print("Failed to load image for url: \(urlString), error: \(error?.description)")
        return
    }

    guard let httpResponse = response as? NSHTTPURLResponse else {
        print("Not an NSHTTPURLResponse from loading url: \(urlString)")
        return
    }

    if httpResponse.statusCode != 200 {
        print("Bad response statusCode: \(httpResponse.statusCode) while loading url: \(urlString)")
        return
    }

    dispatch_async(dispatch_get_main_queue(), { () -> Void in
        self.myImageView.image = UIImage(data: data!)
    })

    }.resume()

Answer 3

可以从URL加载NSData并将其转换为图像并将其粘贴到图像视图中,但这是一个非常糟糕的主意,因为它涉及在主线程上执行同步URL下载.这将锁定UI并可能导致用户认为如果图像下载速度非常快,您的应用程序已崩溃.

编辑:为了澄清,原来的问题在我看来就像海报想要说的一样

imageView.image = [UIImage imageWithContentsOfURL:theURL];

因此我的答案.通过NSData可以做到相同,但这是一个坏主意.相反,应该使用NSURLConnection异步下载图像,并且只有在完全下载后才能将其转换为UIImage并分配给图像视图.

Answer 4

我正在使用https://github.com/rs/SDWebImage这是一个设计精美的库,它可以选择放置占位符图像,无论是内存还是磁盘缓存图像或使用独立于a的下载器UIImageView.

我试图自己做,但图书馆消除了所有的痛苦.

您需要做的就是为您的案例编写以下代码:

#import "UIImageView+WebCache.h"

[imageView sd_setImageWithURL:[NSURL URLWithString:@"http://www.domain.com/path/to/image.jpg"] placeholderImage:[UIImage imageNamed:@"placeholder.png"]];

对我来说就像一个魅力.

Answer 5

如果你想在ImageView中显示来自Url的图像,并且还希望将此图像保存在缓存中以优化到服务器交互,这将有助于您只需将imageView对象和字符串Url传递给此函数

-(void)downloadingServerImageFromUrl:(UIImageView*)imgView AndUrl:(NSString*)strUrl{


strUrl = [strUrl encodeUrl];

NSString* theFileName = [NSString stringWithFormat:@"%@.png",[[strUrl lastPathComponent] stringByDeletingPathExtension]];


NSFileManager *fileManager =[NSFileManager defaultManager];
NSString *fileName = [NSHomeDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"tmp/%@",theFileName]];



imgView.backgroundColor = [UIColor darkGrayColor];
UIActivityIndicatorView *actView = [[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
[imgView addSubview:actView];
[actView startAnimating];
CGSize boundsSize = imgView.bounds.size;
CGRect frameToCenter = actView.frame;
// center horizontally
if (frameToCenter.size.width < boundsSize.width)
    frameToCenter.origin.x = (boundsSize.width - frameToCenter.size.width) / 2;
else
    frameToCenter.origin.x = 0;

// center vertically
if (frameToCenter.size.height < boundsSize.height)
    frameToCenter.origin.y = (boundsSize.height - frameToCenter.size.height) / 2;
else
    frameToCenter.origin.y = 0;

actView.frame = frameToCenter;


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

    NSData *dataFromFile = nil;
    NSData *dataFromUrl = nil;

    dataFromFile = [fileManager contentsAtPath:fileName];
    if(dataFromFile==nil){
        dataFromUrl=[[[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:strUrl]] autorelease];                      
    }

    dispatch_sync(dispatch_get_main_queue(), ^{

        if(dataFromFile!=nil){
            imgView.image = [UIImage imageWithData:dataFromFile];
        }else if(dataFromUrl!=nil){
            imgView.image = [UIImage imageWithData:dataFromUrl];  
            NSString *fileName = [NSHomeDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"tmp/%@",theFileName]];

            BOOL filecreationSuccess = [fileManager createFileAtPath:fileName contents:dataFromUrl attributes:nil];       
            if(filecreationSuccess == NO){
                NSLog(@"Failed to create the html file");
            }

        }else{
            imgView.image = [UIImage imageNamed:@"NO_Image.png"];  
        }
        [actView removeFromSuperview];
        [actView release];
        [imgView setBackgroundColor:[UIColor clearColor]];
    });
});


}