I am working on an app (swift) where i need to load a web page inside UIWebView. Inside that UIWebView there's an <img src="http://www.example.com/uploads/43454.jpg" /> element.
All works fine in this scenario, but the problem is that my 43454.jpg image can be of 5-10 megabytes everytime. So when the UIWebView loads it keeps on loading image for about 2 minutes. Plus this <img> tag can have random sources i.e. 22234.jpg, 98734.jpg, 33123.jpg, and so on.
So to tackle this situation I am trying to use following approach:
List all possible images that we need to show in UIWebView, download and cache them (used Kingfisher library for this purpose) at aplication's startup.
When my UIWebView loads my URL initially, it has nothing in it's <img> elements src attribute, but have a data-image-name="22234.jpg" attribute-value pair.
Now when UIWebView finishes loading its contents, get the image name value from data-image-name attribute.
Check for that image in cache, and update the <img> element's src attribute with that image from cache.
This way UIWebView won't be downloading the image over and over again.
Note: Assuming that UIWebView automatically manages resource cache. All other file types *.js, *.css are being properly cached and not being loaded over and over again. The same doesn't go for images, don't know why.
If this approach seems okay, then how should I accomplish it (Swift 2.2)?
Any quick help will be much appreciated. Thanks
This seems to be the same situation in one of my projects. I had exactly this same scenario. I am going to paste my code here, may be it helps you figure out your solution.
As soon as my app loads I create an array of image URLs and pass it to Kingfisher library to download and cache all images (to disk).
for url in response {
let URL = NSURL(string: url as! String)!
self.PlanImagesArray.append(URL)
}
let prefetcher = ImagePrefetcher(
urls: self.PlanImagesArray,
optionsInfo: nil,
progressBlock: {
(skippedResources, failedResources, completedResources) -> () in
print("progress resources are prefetched: \(completedResources)")
print("progress resources are failedResources: \(failedResources)")
print("progress resources are skippedResources: \(skippedResources)")
},
completionHandler: {
(skippedResources, failedResources, completedResources) -> () in
print("These resources are prefetched: \(completedResources)")
print("These resources are failedResources: \(failedResources)")
print("These resources are skippedResources: \(skippedResources)")
self.activityLoadingIndicator.stopAnimating()
})
prefetcher.start()
At my web view screen I initially loaded my web view and after that used following code to check for particular image in cache and if found converted it into a base64 string and put it back in src attribute of the element.
func webViewDidFinishLoad(webView : UIWebView) {
//UIApplication.sharedApplication().networkActivityIndicatorVisible = false
print("webViewDidFinishLoad")
let xlinkHref = webView.stringByEvaluatingJavaScriptFromString("document.getElementById('background_image').getAttribute('xlink:href')")
//print("xlink:href before = \(webView.stringByEvaluatingJavaScriptFromString("document.getElementById('background_image').getAttribute('xlink:href')"))")
if xlinkHref == "" {
let imageCacheKey = webView.stringByEvaluatingJavaScriptFromString("document.getElementById('background_image').getAttribute('data-cache-key')")
let imageCachePath = ImageCache.defaultCache.cachePathForKey(imageCacheKey! as String)
var strBase64:String = ""
webView.stringByEvaluatingJavaScriptFromString(
"var script = document.createElement('script');" +
"script.type = 'text/javascript';" +
"script.text = \"function setAttributeOnFly(elemName, attName, attValue) { " +
"document.getElementById(elemName).setAttribute(attName, attValue);" +
"}\";" +
"document.getElementsByTagName('head')[0].appendChild(script);"
)!
if(imageCachePath != "") {
ImageCache.defaultCache.retrieveImageForKey(imageCacheKey! as String, options: nil) { (imageCacheObject, imageCacheType) -> () in
let imageData:NSData = UIImageJPEGRepresentation(imageCacheObject!, 100)!
strBase64 = "data:image/jpg;base64," + imageData.base64EncodedStringWithOptions(.EncodingEndLineWithCarriageReturn)
webView.stringByEvaluatingJavaScriptFromString("setAttributeOnFly('background_image', 'xlink:href', '\(strBase64)');")!
}
} else {
webView.stringByEvaluatingJavaScriptFromString("setAttributeOnFly('background_image', 'xlink:href', '\(imageCacheKey)');")!
}
}
Hope it helps.
It sounds like you're basically saying "I know what the images are ahead of time, so I don't want to wait for the UIWebView to load them from the server every time. I want the html to use my local copies instead."
While it's a hack, my first thought was:
Have 2 UIWebViews: one is visible to the user and the other is hidden.
"Trigger" the real page in the hidden UIWebView. When the HTML reaches you...
Create a new string, that is a copy of that HTML, but with the image tags that say <img src="http://... replaced with <img src=\"file://... and pointing to the correct image(s) on disk.
Now tell the visible UIWebView to load that HTML string you built in step 3.
Related
I'm creating an application in ios where I load images from an api using a UITableView and UITableViewCell.
Since the UITableView reuses cells, old images were appearing when I scroll fast. In order to prevent this, I set a default image using a system image(SF symbols).
I also use a cache to store urls to images.
Everything works as it should but now I think of it I'm sending a network request to retrieve that systemImage each time which seems incredibly inefficient since I was using a cache in order to reduce the total network calls in the first place.
Is there way around this or is this a tradeoff I must make?
Code is below.
//use default image from SF symbols
let defaulticon = UIImage(systemName: "photo")?.withTintColor(.gray, renderingMode: .alwaysOriginal)
DispatchQueue.main.async {
cell.mealImage.image = defaulticon
}
guard cell.meal?.strMealThumb != nil else {
print("Category Image doesn't exist")
return
}
//use cache
if let imageData = model.imagecache.object(forKey: cell.meal!.strMealThumb as NSString) {
print("using cache")
DispatchQueue.main.async {
cell.mealImage.image = imageData
}
}
else {
let url = URL(string: cell.meal!.strMealThumb)
let session = URLSession.shared.dataTask(with: url!) { data, response, error in
if error == nil && data != nil {
let image = UIImage(data: data!)
//self.model.imagecache[cell.meal!.strMealThumb] = image
self.model.imagecache.setObject(image!, forKey: cell.meal!.strMealThumb as NSString)
DispatchQueue.main.async {
cell.mealImage.image = image
}
}
}
session.resume()
}
}
Override prepareForReuse method in UITableViewCell and add code in this function to clean up unrequited data that could persist from previous usage of the cell. In your example assign the default image in this function to produce better result.
You asked:
I set a default image using a system image(SF symbols).
...
Everything works as it should but now I think of it I'm sending a network request to retrieve that systemImage each time which seems incredibly inefficient since I was using a cache in order to reduce the total network calls in the first place.
No, UIImage(systemName:) does not make a network request. And it caches the image, itself, as the documentation says:
This method checks the system caches for an image with the specified name and returns the variant of that image that is best suited for the main screen. If a matching image object is not already in the cache, this method creates the image from the specified system symbol image. The system may purge cached image data at any time to free up memory. Purging occurs only for images that are in the cache but are not currently being used.
FWIW, you can empirically verify that this does not perform a network request disconnecting from the network and trying to use it. You will see it works fine, even when disconnected.
FWIW, there is a very small performance gain (less than a millisecond?) by keeping a reference to that tinted system image and reusing it, rather than fetching the cached system image and re-tinting it. But the performance improvement is negligible.
I have an Action Extension to which I'm trying to share PDF-files.
I'm using the boilerplate code for ActionRequestHandler.swift that was autogenerated for me:
func beginRequest(with context: NSExtensionContext) {
// Do not call super in an Action extension with no user interface
self.extensionContext = context
for item in context.inputItems as! [NSExtensionItem] {
if let attachments = item.attachments {
for itemProvider in attachments {
...
...
}
}
}
}
Working from other apps
When exporting from every application except Safari, this is what I get:
This is all ok, I can verify that it's an pdf by checking the com.adobe.pdf and then I use the public.file-url to fetch the shared file.
Failing from Safari
But when exporting from Safari (doesn't matter if I choose "Automatic" or "Pdf" for file type), I instead only get com.apple.property-list:
Further info
Both dropbox and OneDrive works, so it's doable in some sort of way.
Also I realised that sharing an PDF from a url that's protected by some sort of login doesn't work with "Public.file-url" since that URL wont be accessible from inside swift-code.
That leads me to think that the java-script preprocessor might be the way to go? Fetch the pdf-contents with JS and pass it on to code?
Question
How do I use the com.apple.property-list to fetch the file?
Or is some config I did faulty, since I get this property-list instead of the pdf/url combo?
While I didn't manage to figure out a solution to the original question, I did manage to solve the problem.
When adding an Action Extension, one gets to choose Action type:
Presents user interface
No user interface
I choosed No user interfacesince that was what I wanted.
That gave me an Action.js file and ActionRequestHandler.swift:
class ActionRequestHandler: NSObject, NSExtensionRequestHandling {
...
}
These files seem to work around a system where the Action.js is supposed to fetch/manipulate the source page and then send information to the backing Swift code. As stated in my original question, when sharing a PDF from Safari, no PDF-URL gets attached.
A working solution
If I instead choose Presents user interface, I got another setup, ActionViewController.swift:
class ActionViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Get the item[s] we're handling from the extension context.
for item in self.extensionContext!.inputItems as! [NSExtensionItem] {
for provider in item.attachments! {
if provider.hasItemConformingToTypeIdentifier(kUTTypePDF as String) {
provider.loadItem(forTypeIdentifier: kUTTypePDF as String, options: nil, completionHandler: { (pdfUrl, error) in
OperationQueue.main.addOperation {
if let pdfUrl = pdfUrl as? URL {
// pdfUrl now contains the path to the shared pdf data
}
}
}
}
}
This file / solution works as expected, the extensionContext gets populated with one attachment that conforms to kUTTypePDF as expected.
Why this works, while the "no gui"-approach doesn't, I have no idea. Bug or feature?
I have not found any documentation of how/why this is supposed to work in Apple's developer section, the "share extension" documentation is very light.
I am trying to download my images to my table view on the home page for a project. I have retrieved the URLs from the API and they are valid (Printed in terminal)
I am then dumping these URLs into an array let imageURL = [String]()
I looped through the urls and requested the images through the AlamofireImage, but they are not get displayed
for url in self.imagesURL {
ItemImages.removeAll()
Alamofire.request(url).responseImage(completionHandler: { (response) in
guard let image = response.result.value else {return}
self.ItemImages.append(image)
completed(true)
})
}
next I am looking to convert these urls into images to be displayed..If someone could help me on where to move forward next that would be great.Or if I am going wrong anywhere...
I am Load Html File to webview using load html string method. All works fine. in my code user choose image as profile and choosen image save on fix path and name. when user choose image and when web view reload at that time image show old image. image updated to directory but not show.
This problem only occure in Ipad, In Iphone work fine.
Have any Suggestion.? then please suggest
//My Loading Code
webview.loadHTMLString(invoiceHTML, baseURL: NSURL(string:resumeComposer.HTMLFilePath)! as URL)
//Image Source update to HTML String code
imgPath = URL(fileURLWithPath: folderpathforNormal).appendingPathComponent("ProfileImg.png").path
HTMLContent = HTMLContent?.replacingOccurrences(of: "*userimage*", with: imgPath)
clear the UIWebview cache first like this:
//to remove cache from UIWebview
URLCache.shared.removeAllCachedResponses()
if let cookies = HTTPCookieStorage.shared.cookies {
for cookie in cookies {
HTTPCookieStorage.shared.deleteCookie(cookie)
}
}
I have silly problem with loading image from the file. I have two views putted to UITabBarController.
At the first view user can load his image from the Photo Library or Camera. Second view present this photo. This file is on the server. If user doesn't choose his image server sent custom image. If there is uploaded photo it will push user's picture.
When user tap button there is a menu with options. For example we will decide to take picture from the Photo Library. After user took image:
func imagePickerController(picker: UIImagePickerController, didFinishPickingImage image: UIImage!, editingInfo: [NSObject : AnyObject]!) {
self.saveUserImage(userID, imageData: UIImagePNGRepresentation(image)!)
apiManager.userUploadProfile(userID, imageData: UIImagePNGRepresentation(image)!)
userImageView.image = image
}
func saveUserImage(userUUID: String, imageData: NSData) {
let path = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true).last
let savePath = path! + "/\(userUUID)-user.png"
NSFileManager.defaultManager().createFileAtPath(savePath, contents: imageData, attributes: nil)
}
After that point user can see chosen picture and everything is okey. When user change tab, second view will refresh all data on it and again will download all images and data from the server. Unfortunately images that contains old user image doesn't refresh and there is still old photo.
When we come back to the first tab image is going back to old image but after few seconds.
The strangest thing is if I am checking server there is new uploaded image and in the app container it exist too. When I restart the app everything works perfectly.
It looks like this image is saved in the memory and iOS takes old version from RAM or from some other swap. How refresh UIImageView and show current saved image?
EDIT:
There is a method which load the image
func userProfilePicture(userId: String) -> UIImage {
let cacheDirectory = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true).last
let savePath = cacheDirectory! + "/\(userId)-user.png"
if NSFileManager.defaultManager().fileExistsAtPath(savePath) {
if let image = UIImage(named: savePath) {
return image
}
}
return UIImage(named: "test_avatar")!
}
I can't comment but i was facing a similar issue but i have a question, does the picture get uploaded before the user changes tabs, or after? Even if you call the function to update the database, it takes some time to actually "send the new photo/path to the photo to the database". Here are your options, if the picture is not in the server at the time of the switching tabs, implement a loading ui until it has successfully uploaded and the new, updated value, into the database. An easy way to do that would be to use the SVProgressHUD pod and set the default mask type to .clear which disables user interaction. Option 2, is to pass the actual UIImage via a static variable, or in the prepare for segue method, or through a struct, or any other way and set the picture that needs to be refreshed to the uiimage without getting it from the server only when you switch tabs.
Okey, I found the answer. The problem was in initialize UIImage. We have two methods to load image from file.
First one load the image and cache it in memory. Later it use only a reference to this image data in memory:
let image = UIImage(named: savePath)
Second method load image strictly from file every time when user use that function:
let image = UIImage(contentsOfFile: savePath)
Right now it works perfectly :D