I am trying to download images but it is crucial that the images I download are in a specific order. I am using the following code to download the image:
func downloadImage(url: NSURL, completionHandler: (response: UIImage) -> ()){
print("Started downloading \"\(url.URLByDeletingPathExtension!.lastPathComponent!)\".")
manager.getDataFromUrl(url) { (data, response, error) in
dispatch_async(dispatch_get_main_queue()) { () -> Void in
guard let data = data where error == nil else { return }
print("Finished downloading \"\(url.URLByDeletingPathExtension!.lastPathComponent!)\".")
completionHandler(response: UIImage(data: data)!)
}
}
}
and I am using this code to call downloadImage
self.downloadImage(NSURL(string: self.url)!, completionHandler: { response in
dispatch_async(dispatch_get_main_queue()) {
self.images.append(response)
}
})
The problem is that the images start downloading in the correct order however the response isn't (this is obviously because the size of the images are different and one comes in faster). So what is happening is that all images start downloading, and whichever comes first appends to the images : [UIImage] array. How can I make it so that the images in the images array is in order?
I've also tried to remove the main block when calling downloadImage function
self.downloadImage(NSURL(string: self.url)!, completionHandler: { response in
self.images.append(response)
})
You cannot control the download order in the sense that all the requests to the same server will be pipelined no matter what the order you create the URL objects in. Also, some URLs may be cached while others may need to go to the remote server. What you need to do is maintain a mutable array or dictionary that contains the url to actual data mapping, then wait until all the urls have been completely downloaded and then iterate in a known order.
The simplest method is that you can save every image in Dictionary with their url after downloading. Like var imageData = [String: NSData](). Later you can sort it or use it by keys(url).
Related
I'm using firebase with swift.
Below is my code to upload an image from an image picker, and to store the download url of the image.
the point of my code is to store the download url after uploading the image. So I'm trying to find a way to wait for the upload process to finish in order to proceed.
_ = imageRef.putData(data, metadata: nil, completion: {(metadata,error) in
guard let metadata = metadata
else{
print(error)
return
}
})
imageRef.downloadURL { (URL, error) -> Void in
if (error != nil) {
// Handle any errors
} else {
// Get the download URL for 'images/stars.jpg'
let UrlString = URL?.absoluteString}
That's what the completion handler is for. You're already passing a completion handler to putData, which will be invoked when the upload is finished. You should check the error object to make sure it completed successfully.
This is documented, along with a code sample. You can see in the sample that the download URL is fetched from inside the completion handler, only if there is no error.
I'm working on an app that has to load some images and data from server on every launch (to make sure it's using up-to-date info). I'm using Firestore as a DB and currently storing images in it as an URL to Firebase storage.
Is it somehow possible to store an actual image in Firestore? And how can I cache loaded image? Either from
UIImage(contentsOf: URL)
or from Firestore?
Try this Asynchronous image downloader with cache support as a UIImageView category - http://cocoadocs.org/docsets/SDWebImage
It is called sdwebimage really easy to use
I don't know if that's the most efficient way of solving my problem but I did it the following way:
In my Firestore DB I stored references to images in Cloud Storage. Then when app starts for the first time, it loads those files from Firestore DB using default methods AND saves those images in app's container (Documents folder) using Swift's FileManager().
Next time the app starts, it goes through references array and skips the files which are already in app's container.
You could use the bytes type in Firestore (see a list of types) to save whatever binary data you want (use NSData on iOS), but this is almost certainly not what you actually want to do. The limit for the size of an entire document is 1 MB, and images can easily exceed that. Also, you'll be paying the cost of downloading that image to the client any time that document is read, which could be wasteful.
You'll be far better off storing the actual file data in Cloud Storage (using the Firebase SDK on the client), then storing a reference or URL to that in the document, and fetch it from there only when needed.
You could use https://github.com/pinterest/PINRemoteImage, this framework use https://github.com/pinterest/PINCache
import PINRemoteImage
extension UIImageView {
public func setImageFrom(urlString: String!, animated: Bool = false) {
guard let urlString = urlString else {
return
}
guard let url = URL(string: urlString) else {
return
}
layer.removeAllAnimations()
pin_cancelImageDownload()
image = nil
if !animated {
pin_setImage(from: url)
} else {
pin_setImage(from: url, completion: { [weak self] result in
guard let _self = self else { return }
_self.alpha = 0
UIView.transition(with: _self, duration: 0.5, options: [], animations: { () -> Void in
_self.image = result.image
_self.alpha = 1
}, completion: nil)
})
}
}
}
....
UIImageView(). setImageFrom(urlString: "https://ssssss")
I'm trying to download an image called "aaa.jpeg" in my s3 bucket using AWSMobileHubHelper. I found this function on their documentation site.
func downloadContent(content: AWSContent, pinOnCompletion: Bool) {
content.downloadWithDownloadType( .Always, pinOnCompletion: pinOnCompletion, progressBlock: {(content: AWSContent?, progress: NSProgress?) -> Void in
// Handle progress feedback
}, completionHandler: {(content: AWSContent?, data: NSData?, error: NSError?) -> Void in
if let error = error {
print("Failed to download a content from a server.)")
// Handle error here
return
}
// Handle successful download here
if let image = UIImage(data: data!){
self.imageView = image
}
})
}
Once the download is successful (it Did, There is no error message), I'm trying to assign the image to an imageView.
I can tell that the data has been downloaded successfully. I can print the data and see a familiar binary structure of an image. But for some reasons I can't assign the UIImage to the imageView. Because I can't convert the data to a UIImage.
I just want to know if this is the proper way to download image from s3 or am I missing something. Does "data" in the completion block carry the downloaded image? I can't seem to find any documentations on this.
Is this the correct function to use to download from S3?
Yes, the data contains the actual image data. You can put the downloaded data in an UIImageViewController and it should open up fine. Also, this is demonstrated in a Sample App which can be downloaded from the Mobile Hub Console.
I have two UIImageView objects on my view stored inside an array called imgViews and I try to download images for them asynchronously with this code:
func showPic(positionIndex: Int){
let urlStr = "https://www.friendesque.com/arranged/userpics/amir/1"
let url = NSURL(string: urlStr)
let session = NSURLSession.sharedSession()
let task = session.dataTaskWithURL(url!, completionHandler: { (data, response, error) -> Void in
if error == nil {
self.imgViews[positionIndex].image = UIImage(data: data)
//self.imgViews[positionIndex].image = UIImage(named: "11665489_10154101221228009_2542754962143804380_n.jpg")
print("Loading Done...")
}
else{
print(error)
}
})
task.resume()
}
and inside my viewDidLoad(), I have
showPic(0)
When I run the code, I see "Loading Done..." immediately which means the picture has been loaded but it takes a very long time (about 1 min) for the UIImageView to actually change to the loaded picture. It's a very small picture (~15K) and it can't be a processing time problem.
I tried loading a resource image (the comment part of the code) instead of the downloaded picture but it's still slow.
I'm really confused. Why is swift so slow at working with images inside a block?
Perhaps when the data task returns it is on a background thread? You will need to switch to the main thread to change a UIImageView. Regardless I would use the UIImageView+AFNetworking category to achieve this. It's simple, well tested and lets you provide a placeholder image to display while it is downloading.
https://github.com/AFNetworking/AFNetworking/blob/master/UIKit%2BAFNetworking/UIImageView%2BAFNetworking.h
to use:
myImageView.setImageWithURL(url!)
i want to get some extra info about the images i'll share with the Share extension. I can create the UIImage from the url but when i want to obtain an ALAsset i get nil. Anyone had this problem?
itemProvider!.loadItemForTypeIdentifier(String(kUTTypeImage), options: nil, completionHandler: { (decoder: NSSecureCoding!, error: NSError!) -> Void in
if ALAssetsLibrary.authorizationStatus() == ALAuthorizationStatus.Authorized {
if let url = decoder as? NSURL {
ALAssetsLibrary().assetForURL(url, resultBlock: { (myasset:ALAsset!) -> Void in
println(url)
println(fm.fileExistsAtPath(url.path!))
println(myasset)
let location = myasset?.valueForProperty(ALAssetPropertyLocation) as CLLocation?
let date = myasset?.valueForProperty(ALAssetPropertyDate) as NSDate?
self.extensionContext?.completeRequestReturningItems([AnyObject](), completionHandler: nil)
}, failureBlock: { (myerror:NSError!) -> Void in
})
}
}
The output is
file:///var/mobile/Media/DCIM/102APPLE/IMG_2977.JPG
true
nil
the immediate issue is you are passing a file url in place of an asset url for this line: ALAssetsLibrary().assetForURL(url, resultBlock: { (myasset:ALAsset!) -> Void in.
Share extensions return the url to the path on the iphone's file system...something of the form: file:///..... These are not the same as the urls that an ALAsset require in the assetForURL method.
Unfortunately, though this makes the code more correct, it still doesn't fix the issue. I spent some time with many different approaches. Writing a new image to disk via the AssetsLibrary and the given file path will return an asset url upon completion which will work successfully - though you obviously don't want duplicate photos in your camera roll. (Note: there is no way to delete an ALAsset). You could probably hold onto the file path and delete the new image when you are done with it, but that is an extremely messy approach.
I ended up rewriting my approach given these limitations.