Can I load a UIImage from a URL?
I have a URL for an image (got it from UIImagePickerController) but I no longer have the image in memory (the URL was saved from a previous run of the app). Can I reload the UIImage from the URL again?
I see that UIImage has a imageWithContentsOfFile: but I have a URL. Can I use NSData's dataWithContentsOfURL: to read the URL?
EDIT1
based on @Daniel's answer I tried the following code but it doesn't work...
NSLog(@"%s %@", __PRETTY_FUNCTION__, photoURL);
if (photoURL) {
NSURL* aURL = [NSURL URLWithString:photoURL];
NSData* data = [[NSData alloc] initWithContentsOfURL:aURL];
self.photoImage = [UIImage imageWithData:data];
[data release];
}
When I ran it the console shows:
-[PhotoBox willMoveToWindow:] file://localhost/Users/gary/Library/Application%20Support/iPhone%20Simulator/3.2/Media/DCIM/100APPLE/IMG_0004.JPG
*** -[NSURL length]: unrecognized selector sent to instance 0x536fbe0
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[NSURL length]: unrecognized selector sent to instance 0x536fbe0'
Looking at the call stack, I'm calling URLWithString, which calls URLWithString:relativeToURL:, then initWithString:relativeToURL:, then _CFStringIsLegalURLString, then CFStringGetLength, then forwarding_prep_0, then forwarding, then -[NSObject doesNotRecognizeSelector].
Any ideas why my NSString (photoURL's address is 0x536fbe0) doesn't respond to length? Why does it say it doesn't respond to -[NSURL length]? Doesn't it know that param is an NSString, not a NSURL?
EDIT2
OK, the only problem with the code is the string to URL conversion. If I hardcode the string, everything else works fine. So something is wrong with my NSString and if I can't figure it out, I guess that should go in as a different开发者_StackOverflow社区 question. With this line inserted (I pasted the path from the console log above), it works fine:
photoURL = @"file://localhost/Users/gary/Library/Application%20Support/iPhone%20Simulator/3.2/Media/DCIM/100APPLE/IMG_0004.JPG";
You can do it this way (synchronously, but compact):
UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:MyURL]]];
A much better approach is to use Apple's LazyTableImages to preserve interactivity.
You can try SDWebImage, it provides:
- Asynchronous loading
- Caching for offline use
- Place holder image to appear while loading
- Works well with UITableView
Quick example:
[cell.imageView setImageWithURL:[NSURL URLWithString:@"http://www.domain.com/path/to/image.jpg"] placeholderImage:[UIImage imageNamed:@"placeholder.png"]];
And the swift version :
let url = NSURL.URLWithString("http://live-wallpaper.net/iphone/img/app/i/p/iphone-4s-wallpapers-mobile-backgrounds-dark_2466f886de3472ef1fa968033f1da3e1_raw_1087fae1932cec8837695934b7eb1250_raw.jpg");
var err: NSError?
var imageData :NSData = NSData.dataWithContentsOfURL(url,options: NSDataReadingOptions.DataReadingMappedIfSafe, error: &err)
var bgImage = UIImage(data:imageData)
If you're really, absolutely positively sure that the NSURL is a file url, i.e. [url isFileURL] is guaranteed to return true in your case, then you can simply use:
[UIImage imageWithContentsOfFile:url.path]
get DLImageLoader and try folowing code
[DLImageLoader loadImageFromURL:imageURL
completed:^(NSError *error, NSData *imgData) {
imageView.image = [UIImage imageWithData:imgData];
[imageView setContentMode:UIViewContentModeCenter];
}];
Another typical real-world example of using DLImageLoader, which may help someone...
PFObject *aFacebookUser = [self.fbFriends objectAtIndex:thisRow];
NSString *facebookImageURL = [NSString stringWithFormat:
@"http://graph.facebook.com/%@/picture?type=large",
[aFacebookUser objectForKey:@"id"] ];
__weak UIImageView *loadMe = self.userSmallAvatarImage;
// ~~note~~ you my, but usually DO NOT, want a weak ref
[DLImageLoader loadImageFromURL:facebookImageURL
completed:^(NSError *error, NSData *imgData)
{
if ( loadMe == nil ) return;
if (error == nil)
{
UIImage *image = [UIImage imageWithData:imgData];
image = [image ourImageScaler];
loadMe.image = image;
}
else
{
// an error when loading the image from the net
}
}];
As I mention above another great library to consider these days is Haneke (unfortunately it's not as lightweight).
Try this code, you can set loading image with it, so the users knows that your app is loading an image from url:
UIImageView *yourImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"loading.png"]];
[yourImageView setContentMode:UIViewContentModeScaleAspectFit];
//Request image data from the URL:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSData *imgData = [NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://yourdomain.com/yourimg.png"]];
dispatch_async(dispatch_get_main_queue(), ^{
if (imgData)
{
//Load the data into an UIImage:
UIImage *image = [UIImage imageWithData:imgData];
//Check if your image loaded successfully:
if (image)
{
yourImageView.image = image;
}
else
{
//Failed to load the data into an UIImage:
yourImageView.image = [UIImage imageNamed:@"no-data-image.png"];
}
}
else
{
//Failed to get the image data:
yourImageView.image = [UIImage imageNamed:@"no-data-image.png"];
}
});
});
Check out the AsyncImageView provided over here. Some good example code, and might even be usable right "out of the box" for you.
AFNetworking provides async image loading into a UIImageView with placeholder support. It also supports async networking for working with APIs in general.
Make sure enable this settings from iOS 9:
App Transport Security Settings in Info.plist to ensure loading image from URL so that it will allow download image and set it.
And write this code:
NSURL *url = [[NSURL alloc]initWithString:@"http://feelgrafix.com/data/images/images-1.jpg"];
NSData *data =[NSData dataWithContentsOfURL:url];
quickViewImage.image = [UIImage imageWithData:data];
The way using a Swift Extension to UIImageView (source code here):
Creating Computed Property for Associated UIActivityIndicatorView
import Foundation
import UIKit
import ObjectiveC
private var activityIndicatorAssociationKey: UInt8 = 0
extension UIImageView {
//Associated Object as Computed Property
var activityIndicator: UIActivityIndicatorView! {
get {
return objc_getAssociatedObject(self, &activityIndicatorAssociationKey) as? UIActivityIndicatorView
}
set(newValue) {
objc_setAssociatedObject(self, &activityIndicatorAssociationKey, newValue, UInt(OBJC_ASSOCIATION_RETAIN))
}
}
private func ensureActivityIndicatorIsAnimating() {
if (self.activityIndicator == nil) {
self.activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: UIActivityIndicatorViewStyle.Gray)
self.activityIndicator.hidesWhenStopped = true
let size = self.frame.size;
self.activityIndicator.center = CGPoint(x: size.width/2, y: size.height/2);
NSOperationQueue.mainQueue().addOperationWithBlock({ () -> Void in
self.addSubview(self.activityIndicator)
self.activityIndicator.startAnimating()
})
}
}
Custom Initializer and Setter
convenience init(URL: NSURL, errorImage: UIImage? = nil) {
self.init()
self.setImageFromURL(URL)
}
func setImageFromURL(URL: NSURL, errorImage: UIImage? = nil) {
self.ensureActivityIndicatorIsAnimating()
let downloadTask = NSURLSession.sharedSession().dataTaskWithURL(URL) {(data, response, error) in
if (error == nil) {
NSOperationQueue.mainQueue().addOperationWithBlock({ () -> Void in
self.activityIndicator.stopAnimating()
self.image = UIImage(data: data)
})
}
else {
self.image = errorImage
}
}
downloadTask.resume()
}
}
The Best and easy way to load Image via Url is by this Code:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSData *data =[NSData dataWithContentsOfURL:[NSURL URLWithString:imgUrl]];
dispatch_async(dispatch_get_main_queue(), ^{
imgView.image= [UIImage imageWithData:data];
});
});
Replace imgUrl by your ImageURL
Replace imgView by your UIImageView.
It will load the Image in another Thread, so It will not slow down your App load.
Local URL's are super simple, just use this :
UIImage(contentsOfFile: url.path)
加载中,请稍侯......
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