The project I am working on has an extension that writes data to UserDefaults. Then in the containing app should the UI should get updated according to the changes. The problem is that UserDefaults.didChangeNotification does not get fired unless the screen comes from background. What could be the reason and is there a way to be fixed or another way to get the needed update?
Writing the data in the extension:
let sharedUserDefaults = UserDefaults(suiteName: Common.UserDefaultsSuite)
var receivedNotifications = sharedUserDefaults?.array(forKey: Common.ReceivedNotifications)
if receivedNotifications != nil {
receivedNotifications?.append(aData)
} else {
receivedNotifications = [aData]
}
sharedUserDefaults?.set(receivedNotifications, forKey: Common.ReceivedNotifications)
Registering for the notification in the view controller:
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self, selector: #selector(userDefaultsDidChange), name: UserDefaults.didChangeNotification, object: nil)
}
And working with changed user defaults (that actually does not get called):
#objc func userDefaultsDidChange(_ notification: Notification) {
print("User defaults did change")
gatherReceivedNotifications()
}
Still no idea why the other way doesn't work but the following works so it's a solution. As per suggested here I did the following:
override func viewDidLoad() {
super.viewDidLoad()
UserDefaults(suiteName: Common.UserDefaultsSuite)?.addObserver(self, forKeyPath: Common.ReceivedNotifications, options: .new, context: nil)
}
Then implemented observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?):
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
if keyPath == Common.ReceivedNotifications {
gatherReceivedNotifications()
}
}
It is fired immediately and only when a change to UserDefaults for the key Common.ReceivedNotifications is made.
The code #selector(userDefaultsDidChange) is means func userDefaultsDidChange() without parameter.
But you defined func userDefaultsDidChange(_ notification: Notification), it's have one parameter.
Next step:
Change #selector(userDefaultsDidChange) to #selector(userDefaultsDidChange(_:)) can fixed it.
Related
Screenshot prevention is not possible that i Understand but we can do the same as snapchatdoes,We can Detect it.
My application consist of more than 10+ controller so on every page addobserver is bit tedious so want the solution if i can place it on appdelegate/Scenedelegate or any other so that on whichever controller screenshot Captured i l be notified.Placing is the main required thing here
Something like reachability which works in similar way for network detection
Here is the Code :
func detectScreenShot(action: #escaping () -> ()) {
UIScreen.main.addObserver(self, forKeyPath: "captured", options: .new, context: nil)
let mainQueue = OperationQueue.main
NotificationCenter.default.addObserver(forName: UIApplication.userDidTakeScreenshotNotification, object: nil, queue: mainQueue) { notification in
// executes after screenshot
print(notification)
action()
}
}
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey: Any]?, context: UnsafeMutableRawPointer?) {
if (keyPath == "captured") {
let isCaptured = UIScreen.main.isCaptured
print(isCaptured)
}
}
I think you can implement this by making a BaseViewController,And all the other View Controllers should be inherited by the BaseViewController,So u just have to observe the screenshot detection in BaseViewController and you don't have to write the code on every ViewController
Hi I've been working on using Open Tok For a streaming session
I used MPVolumeView to vary system Sound.
Issue: MPVolumeView does work changing system Volume but that doesn't affect my OTSession Volume
Expected: I want to change "outputVolume" of AVAudioSession running with OpenTok
Code:
func startObservingVolumeChanges() {
avAudioSession.addObserver(self, forKeyPath: Observation.VolumeKey, options: [.initial, .new], context: &Observation.Context)
}
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
if context == &Observation.Context {
if keyPath == Observation.VolumeKey, let volume = (change?[NSKeyValueChangeKey.newKey] as? NSNumber)?.floatValue {
print("Volume: \(volume)")
}
} else {
super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
}
}
func stopObservingVolumeChanges() {
avAudioSession.removeObserver(self, forKeyPath: Observation.VolumeKey, context: &Observation.Context)
}
As soon as I change volume using iOS Volume buttons "Volume does get print from 0 to 1 range"
when I change value using Slider "Volume does get print from 0 to 1 range" but doesn't lower the sound of Session
Please help.
Discussed with OpenTok Developers. This is not supported attaching screenshot for same,
I've posted a more in-depth question to try and get to the bottom of the issue, but in a brief:
I'm attempting to show a PHP/JS-based web application (Laravel) through a WKWebView. However, due to the nature of the script's redirecting properties, the only code I've gotten to actually detect the URL change is with #keyPath(WKWebView.url):
override func viewDidLoad() {
super.viewDidLoad()
webView.navigationDelegate = self
webView.uiDelegate = self
webView.addObserver(self, forKeyPath: #keyPath(WKWebView.url), options: .new, context: nil)
}
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
if keyPath == #keyPath(WKWebView.url) {
print("URL Change:", self.webView.url?.absoluteString ?? "# No value provided")
}
}
However, the output to console is always the same:
URL Change: # No value provided
So I know that the KVO for WKWebView.url is able to fire upon script-based redirection within the WebView. In fact, if you take a look at my other question, it is the only code that can detect this sort of redirection – which is strange, because when launched in Safari (both iOS and macOS), the URL bar is able to reflect those redirected changes to the URL's value. However, when in the WKWebView, none of the WKNavigationDelegate functions are able to detect such a change to the URL.
Is there any way to obtain the URL directly from the keyPath value of WKWebView.url when fired? Are there any alternatives, not described in my previously-mentioned question, that could obtain the URL?
Trying to obtain the URL value from webView.url seems to always return nil.
EDIT: I am able to get the exact URL value with the observerValue function code:
if let key = change?[NSKeyValueChangeKey.newKey] {
print("URL: \(key)") // url value
}
However, I am unable to cast it as a String or pass it to another function otherwise. Is there any way to set this key as a variable, if it .contains("https://")?
I was able to assign the KVO WKWebView.url to a String variable. From there, I was able to pass the String value to a function that then handles each output I'm looking for:
var cURL = ""
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
if let key = change?[NSKeyValueChangeKey.newKey] {
cURL = "\(key)" // Assign key-value to String
print("cURL:", cURL) // Print key-value
cURLChange(url: cURL) // Pass key-value to function
}
}
func cURLChange(url: String) {
if cURL.contains("/projects/new") {
print("User launched new project view")
// Do something
} else {
// Do something else
}
}
A similar solution, using a more modern method (with less hassle), was provided here.
var cURL = ""
var webView: WKWebView!
var webViewURLObserver: NSKeyValueObservation?
override func viewDidLoad() {
super.viewDidLoad()
// 1. Assign changed value to variable
webViewURLObserver = webView.observe(\.url, options: .new) { webView, change in
self.cURL = "\(String(describing: change.newValue))" }
// 2. Print value of WKWebView URL
webViewURLObserver = webView.observe(\.url, options: .new) { webView, change in
print("URL: \(String(describing: change.newValue))"
)}
By using NSKeyValueObservation of an object, you don't need to remove observers or check observer values by keyPath. You can simply set it to observe an object (ie. WKWebView) and run code when a change is observed.
I Would like to display the value of the badge number in a label.
So far i've put everything in my viewWillAppear. So every time the controller is loaded the variable is assigned. Here's the code:
var deliveredNotif = Int()
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(true)
deliveredNotif = UIApplication.shared.applicationIconBadgeNumber
myBadgeLabel.text = "\(deliveredNotif)"
}
My question is:
How can i update deliveredNotif if the controller is active and so viewWillAppear is already been called? Meaning if I am in the controller is there a way to trigger a func which will update the value of deliveredNotif every time the value of applicationIconBadgeNumber is changed?
Thank you!
-------UPDATE----MY SOLUTION
I created a constant variable:
var iconBadgeNumber = NSNumber()
in my Appdelegate i have:
func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: #escaping (UNNotificationPresentationOptions) -> Void) {
completionHandler([.alert, .badge])
NotificationCenter.default.post(name: NSNotification.Name(rawValue: "applicationIconBadgeNumber"), object: nil)
iconBadgeNumber = UIApplication.shared.applicationIconBadgeNumber + 1 as NSNumber
}
and then in my controller:
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self, selector: #selector(updateIconBadgeNumber), name: NSNotification.Name(rawValue: "applicationIconBadgeNumber"), object: nil)
}
#objc func updateIconBadgeNumber() {
if iconBadgeNumber == 0 {
print("zero")
} else {
print("there unread notification")
}
}
You can set your UIViewController as an observer for the key path "applicationIconBadgeNumber":
First register for remote notifications. In your didFinishLaunchingWithOptions function, add:
let center = UNUserNotificationCenter.current()
center.requestAuthorization(options: [.alert, .badge, .sound]) { _, _ in
DispatchQueue.main.async {
application.registerForRemoteNotifications()
}
}
don't forget to add also: import UserNotifications on the top of your file
Then add in your viewDidLoad:
UIApplication.shared.addObserver(self, forKeyPath: "applicationIconBadgeNumber", options: .new, context: nil)
Then, override the observeValue function:
override func observeValue(forKeyPath keyPath: String?,
of object: Any?,
change: [NSKeyValueChangeKey : Any]?,
context: UnsafeMutableRawPointer?) {
if keyPath == "applicationIconBadgeNumber" {
deliveredNotif = UIApplication.shared.applicationIconBadgeNumber
myBadgeLabel.text = "\(deliveredNotif)"
}
}
You have 3 different ways in order to notify an object about a changed value :
First of all you have the Notification center in order to notify an observer when your value changed.
Check out this post, and more informations on the Internet, you will find what you want.
Moreover, you can also use protocol and delegate but it seems kind of heavy for just a notification update on a value.
Finally You should definitely look around this post, it explains the principle of the Key-Value Observing (KVO), I am sure you already heard about it.
And to conclude, the ultimate article, will explain you when you should use each of this principle.
KVO vs NSNotification vs protocol/delegates?
You should try to investigate more seriously before posting a question that is already answered multiple times.
Hope this articles will help you.
I am working on video application. I want to discard the video frames when camera is autofocusing. During autofocus image captured become blurred and image processing for that frame become bad but once autofocus is done, image processing become excellent. Any body give me solution?
adjustingFocus property.
Indicates whether the device is currently adjusting its focus setting. (read-only)
*Notes: You can observe changes to the value of this property using Key-value observing.
iOS 4.0 and later
https://developer.apple.com/library/ios/documentation/AVFoundation/Reference/AVCaptureDevice_Class/Reference/Reference.html#//apple_ref/occ/instp/AVCaptureDevice/adjustingFocus
Following is a sample code in Swift 3.x.
First a observer should be added to the selected capture device at camera initialization.
captureDevice.addObserver(self, forKeyPath: "adjustingFocus", options: [.new], context: nil)
Then observeValue method is overridden. By accessing the optional value returned by the method, autoFocussing frames can be identified.
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
guard let key = keyPath, let changes = change else {
return
}
if key == "adjustingFocus" {
let changedValue = changes[.newKey]
if (changedValue! as! Bool){
// camera is auto-focussing
}else{
// camera is not auto-focussing
}
}
}
Example on Swift 4+
class ViewController: UIViewController, AVCapturePhotoCaptureDelegate {
//#objc var captureDevice: AVCaptureDevice?
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
self.addObservers()
}
func addObservers() {
self.addObserver(self, forKeyPath: "captureDevice.adjustingFocus", options: .new, context: nil)
}
func removeObservers() {
self.removeObserver(self, forKeyPath: "captureDevice.adjustingFocus")
}
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey: Any]?, context: UnsafeMutableRawPointer?) {
if keyPath == "captureDevice.adjustingFocus" {
print("============== adjustingFocus: \(self.captureDevice?.lensPosition)")
}
} //End of class
Observing adjustingFocus is not working for me. It's always no. And I find this.
Note that when traditional contrast detect auto-focus is in use, the AVCaptureDevice adjustingFocus property flips to YES when a focus is underway, and flips back to NO when it is done. When phase detect autofocus is in use, the adjustingFocus property does not flip to YES, as the phase detect method tends to focus more frequently, but in small, sometimes imperceptible amounts. You can observe the AVCaptureDevice lensPosition property to see lens movements that are driven by phase detect AF.
from Apple
I have not try it yet, I will try and update later.
Edit. I have try it, and confirm this's right.