I try to get notifications as soon as the currently visible pages in my pdfView change.
Actually this should work according to the documentation via .PDFViewVisiblePagesChanged.
However, I only get a notification the very first time when the pdfView didLoad.
As soon as I then scroll (and thus the visible pages change) I do not receive a single notification. The funny thing is that the notification .PDFViewPageChanged works normally (but in this case it is not enough). The same behaviour is also with .PDFViewScaleChanged: here I never get a notification when zooming inside the pdfView.
Code Snippet from my ViewController:
ovverride func viewDidLoad() {
//...
NotificationCenter.default.addObserver(self, selector: #selector(onDidVisiblePagesChanged(_:)), name: .PDFViewPageChanged, object: nil)
//...
}
#objc func onDidVisiblePagesChanged(notification:Notification) {
print("visible Pages changed!")
}
The problem is located in your function "onDidVisiblePagesChanged, you're waiting for a parameter type notification, you need to cast the parameter inside your function
#objc func onDidVisiblePagesChanged(_ sender:Any) {
if let notification = sender as? Notification {
print("visible Pages changed!")
print(notification)
}
}
Related
Here I created a customView: UIView and implemented UITextField didBegin and didEnd notificationObservers
When set object as nil. I'm get triggered notificationObserved(_:)
But When I pass a (object: self) I didn't receive notificationObserved.
class CustomView: UIView {
func setupView() {
[UITextField.textDidBeginEditingNotification,
UITextField.textDidEndEditingNotification].forEach({
NotificationCenter.default.addObserver(self, selector: #selector(notificationObserved(_:)), name: $0, object: self)
})
}
#objc func notificationObserved(_ notified: Notification) {
switch notified.name {
case UITextField.textDidBeginEditingNotification:
// Do here
case UITextField.textDidEndEditingNotification:
// Do here
default:
break
}
}
}
That's actually the expected behavior. The parameter object in the method addObserver(_,selector:,name:,object:) is, as stated in the developer documentation (here), "The object that sends notifications to the observer".
Since the object sending the notification is UITextField and not and instance of your class CustomView, you will never get the notification when you pass self in the object parameter.
Passing nil indicates that no matter the sender, you always want to receive the notification.
I have a UIView similar to the one you can see below:
class ViewTaskViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {
override func viewDidLoad() {
super.viewDidLoad()
subscribeToNotifications()
}
func subscribeToNotifications() {
let notification = NotificationCenter.default
notification.addObserver(forName: Notification.Name(rawValue: "TimerUpdated"), object: nil, queue: nil, using: handleUpdateTimer)
print("Subscribed to NotificationCenter in ViewTaskViewController")
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
print("TUFU TUFU TUFU")
NotificationCenter.default.removeObserver(self)
}
deinit {
print("DENINT")
}
#objc func handleUpdateTimer(notification: Notification) {
if let userInfo = notification.userInfo, let timeInSeconds = userInfo["timeInSeconds"] as? Int {
withUnsafePointer(to: &self.view) {
print("We got timeeeeee \(timeInSeconds) \($0)")
}
//do something here....
}
}
}
The issue I am having is that I am unable to remove the observers from this particular UIView when the user hits the back button and returns to another viewController.
ViewWillDisppear is called but deinit is not called. The strange thing is that if we remove subscribeToNotifications() from viewDidLoad() then the deinit is called.
The other issue is related to a memory leak. As you can see in the screenshot below, when the view does subscribe to notifications and the user leaves/re-enters the view, the memory usage increase.
Now compare that to when the subscribeToNotifications() is commented out, there is no increase in memory usage and only one instance of the viewController.
The conclusion is that there seems to be a correlation between the notification subscription creation of a new instance of the UIView hence the deinit is not being called.
I'd like to find out if there is a way we can deinitialize the view and unsubscribe from the notification.
Please let me know if you need further information. :)
I've found the removeObserver() only works if you use this version of addObserver()
notification.addObserver(self, selector:#selector(self.handleUpdateTimer), name: Notification.Name(rawValue: "TimerUpdated"), object: nil)
I'm guessing with the original version you aren't actually indicating who the observer is.
As #Spads said you can use
NotificationCenter.default.addObserver(self, selector: #selector(subscribeToNotifications), name: NSNotification.Name(rawValue: "TimerUpdate"), object: nil)
or the one you already have.
you can remove your notification by it's name or it's reference
NotificationCenter.default.removeObserver(self, name: "TimerUpdate", object: nil)
if you declared your notification at the top of your class then you can directly pass the reference of your notification to be removed in your case notification
NotificationCenter.default.removeObserver(notification)
You should store your newly added observer in a opaque object (NSObjectProtocol) and then call NotificationCenter.default.removeObserver(self.nameOfObserver)
If a switch is turned on, text-to-word spoken every x seconds. The switch is on the first view controller, and the speech occurs after a segue to the second view controller.
Code in the first view controller:
#IBAction func speakwords(sender: AnyObject) {
NSNotificationCenter.defaultCenter().postNotificationName("speaknotif", object: speakwords)
Code in the second view controller:
verride func viewDidLoad() {
NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("talk:"), name: "speaknotif", object: self.view.window)
func talk(notification: NSNotification){guard let count = notification.object else {return}
if Bool(TYPE_BOOL as! NSO) = "true"{
let speechsynth = AVSpeechSynthesizer()}
In your case, Notification Center was useless. Because you are calling post method before adding observer for that notification. So notification concept won't work there.
Instead of this, just set one Bool like "isSwitchSelected". And pass that value to next vc, check if the value is yes, then call func talk method.
I'm working with Intercom's iOS SDK and reading through the Header available I found:
//=========================================================================================================
/*! #name Intercom Notifications */
//=========================================================================================================
/*!
These are notifications thrown by Intercom for iOS when the Intercom window is displayed and hidden or when
a new conversation has been started. These notifications are fired only when there is a change in the state
of Intercom's UI: when a user receives a message for instance, willShow and didShow notifications will be
fired accordingly when the Intercom Notification (chat head) is presented.
Once the user taps on the chat head, the message is presented in your app. It will be presented covering
the entire screen, but no notifications will be thrown here as Intercom has already been visible.
In the case of a new conversation this notification may be used to prompt users to enable push notifications.
*/
let IntercomWindowWillShowNotification: String
let IntercomWindowDidShowNotification: String
let IntercomWindowWillHideNotification: String
let IntercomWindowDidHideNotification: String
let IntercomDidStartNewConversationNotification: String
How can I got about catching these notifications in a controller and then do something based on the specific notification that is thrown?
You will need to add your ViewControllerClass as an observer to each notification it should observe in viewDidLoad...
class ITC: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("icWindowWillShowNotification:"), name: IntercomWindowWillShowNotification, object: nil)
}
deinit {
NSNotificationCenter.defaultCenter().removeObserver(self)
}
func icWindowWillShowNotification (notification: NSNotification) {
//Do something
}
}
I am building an iOS app using the new language Swift. Now it is an HTML5 app, that displays HTML content using the UIWebView. The app has local notifications, and what i want to do is trigger a specific javascript method in the UIWebView when the app enters foreground by clicking (touching) the local notification.
I have had a look at this question, but it does not seem to solve my problem. I have also come across this question which tells me about using UIApplicationState, which is good as that would help me know the the app enters foreground from a notification. But when the app resumes and how do i invoke a method in the viewController of the view that gets displayed when the app resumes?
What i would like to do is get an instance of my ViewController and set a property in it to true. Something as follows
class FirstViewController: UIViewController,UIWebViewDelegate {
var execute:Bool = false;
#IBOutlet var tasksView: UIWebView!
}
And in my AppDelegate i have the method
func applicationWillEnterForeground(application: UIApplication!) {
let viewController = self.window!.rootViewController;
let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
var setViewController = mainStoryboard.instantiateViewControllerWithIdentifier("FirstView") as FirstViewController
setViewController.execute = true;
}
so what i would like to do is when the app enters foreground again, i want to look at the execute variable and run the method as follows,
if execute{
tasksView.stringByEvaluatingJavaScriptFromString("document.getElementById('sample').click()");
}
Where should i put the code for the logic to trigger the javascript from the webview? would it be on viewDidLoad method, or one of the webView delegate methods? i have tried to put that code in the viewDidLoad method but the value of the boolean execute is set to its initial value and not the value set in the delegate when the app enters foreground.
If I want a view controller to be notified when the app is brought back to the foreground, I might just register for the UIApplication.willEnterForegroundNotification notification (bypassing the app delegate method entirely):
class ViewController: UIViewController {
private var observer: NSObjectProtocol?
override func viewDidLoad() {
super.viewDidLoad()
observer = NotificationCenter.default.addObserver(forName: UIApplication.willEnterForegroundNotification, object: nil, queue: .main) { [unowned self] notification in
// do whatever you want when the app is brought back to the foreground
}
}
deinit {
if let observer = observer {
NotificationCenter.default.removeObserver(observer)
}
}
}
Note, in the completion closure, I include [unowned self] to avoid strong reference cycle that prevents the view controller from being deallocated if you happen to reference self inside the block (which you presumably will need to do if you're going to be updating a class variable or do practically anything interesting).
Also note that I remove the observer even though a casual reading of the removeObserver documentation might lead one to conclude is unnecessary:
If your app targets iOS 9.0 and later or macOS 10.11 and later, you don't need to unregister an observer in its dealloc method.
But, when using this block-based rendition, you really do need to remove the notification center observer. As the documentation for addObserver(forName:object:queue:using:) says:
To unregister observations, you pass the object returned by this method to removeObserver(_:). You must invoke removeObserver(_:) or removeObserver(_:name:object:) before any object specified by addObserver(forName:object:queue:using:) is deallocated.
I like to use the Publisher initializer of NotificationCenter. Using that you can subscribe to any NSNotification using Combine.
import UIKit
import Combine
class MyFunkyViewController: UIViewController {
/// The cancel bag containing all the subscriptions.
private var cancelBag: Set<AnyCancellable> = []
override func viewDidLoad() {
super.viewDidLoad()
addSubscribers()
}
/// Adds all the subscribers.
private func addSubscribers() {
NotificationCenter
.Publisher(center: .default,
name: UIApplication.willEnterForegroundNotification)
.sink { [weak self] _ in
self?.doSomething()
}
.store(in: &cancelBag)
}
/// Called when entering foreground.
private func doSomething() {
print("Hello foreground!")
}
}
Add Below Code in ViewController
override func viewDidLoad() {
super.viewDidLoad()
let notificationCenter = NotificationCenter.default
notificationCenter.addObserver(self, selector:#selector(appMovedToForeground), name: UIApplication.willEnterForegroundNotification, object: nil)
}
#objc func appMovedToForeground() {
print("App moved to foreground!")
}
In Swift 3, it replaces and generates the following.
override func viewDidLoad() {
super.viewDidLoad()
foregroundNotification = NotificationCenter.default.addObserver(forName:
NSNotification.Name.UIApplicationWillEnterForeground, object: nil, queue: OperationQueue.main) {
[unowned self] notification in
// do whatever you want when the app is brought back to the foreground
}