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

For such a straightforward task I would highly recommend against integrating projects such as Three20, the library is a monster and not very straightforward to get up and running.

I would instead recommend this approach:

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];
}];

EDIT for 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()

*EDIT for 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

It's possible to load an NSData from a URL and convert that to an image and stick that in the image view, but this is an extremely bad idea because it involves doing a synchronous URL download on the main thread. This will lock up the UI and possibly cause the user to think your app has crashed if the image doesn't download extremely fast.

Edit : To clarify, the original question looks to me like the poster wants to say something along the lines of

imageView.image = [UIImage imageWithContentsOfURL:theURL];

Hence my answer. It's possible to do the equivalent by going through NSData, but it's a bad idea. Instead, the image should be downloaded asynchronously using NSURLConnection, and only once it's fully downloaded should it be converted into a UIImage and assigned to the image view.

Answer 4

I am using https://github.com/rs/SDWebImage which is a beautifully designed library, which has the options to put a placeholder image, whether to memory, or disk cache the image or use the downloader independent of a UIImageView .

I was trying to do that by myself but the library took all the pain away.

All you need to do is to write the code below for your case :

#import "UIImageView+WebCache.h"

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

Worked like a charm for me.

Answer 5

If you want to display image from Url in ImageView, And also want to save this image in cache for optimize to server interaction this would help you Just pass your imageView object and string Url to this function

-(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]];
    });
});


}

Answer 6

Here's an updated answer to the best answer, as imageWithContentsOfURL is no longer a method of UIImage. You'll have to use CIImage:

NSURL *url = [NSURL URLWithString:@"http://url_goes_here.com/logo.png"];
imageView.image = [UIImage imageWithCIImage:[CIImage imageWithContentsOfURL:url]];

Answer 7

Unfortunately this feature is not available as of this writing... instead you will have to implement the functionality yourself by:

1. Downloading the data of the image
2. Saving it or caching it somewhere (db or filesystem) and then
3. Setting the UIImaveView to the saved structure

Fortunately you don't have to break your head coming out with said functionality as Apple provides an example that does exactly that as part of their code samples.

Follow the code and I'm sure you will be able to accommodate it to your needs.

Answer 8

EGOImageLoading

EGOImageView* imageView = [[EGOImageView alloc] initWithPlaceholderImage:[UIImage imageNamed:@"placeholder.png"]];
imageView.frame = CGRectMake(0.0f, 0.0f, 36.0f, 36.0f);

//show the placeholder image instantly
[self.anyView addSubview:imageView];
[imageView release] //if you want

//load the image from url asynchronously with caching automagically
imageView.imageURL = [NSURL URLWithString:photoURL]; 

If you want more, there is a delegate to handle actions after loading

@protocol EGOImageViewDelegate<NSObject>
@optional
- (void)imageViewLoadedImage:(EGOImageView*)imageView;
- (void)imageViewFailedToLoadImage:(EGOImageView*)imageView error:(NSError*)error;
@end

Answer 9

Another option is TTImageView from the Three20 library which handles asynchronous loading of an image. The control works great. However, the downside is you have to deal with the nightmare of installing Three20 (which is then almost impossible to fully remove).

Answer 10

use AFNetworking category UIImageView+AFNetworking.h

 #import "UIImageView+AFNetworking.h


[profileImageView setImageWithURL:[NSURL URLWithString:photoURL] placeholderImage:[UIImage imageNamed:@"placeholder"]];