Many im services automatically display messages once the user on the other end has sent a message.
Right now, the only way I can think of to do this is to use an nstimer which will run the appropriate block of code which fetches the messages and updates the table view. This is resources intensive and can waste one of the requests per second. Is there any way to automate this process and make it happen only when a new message has been sent/received?
Here's an example of using didReceiveRemoteNotification inside of your app delegate to respond to push notifications. In particular, you care about the case where you are receiving the notification while the app is active.
func application(application: UIApplication, didReceiveRemoteNotification userInfo: [NSObject : AnyObject]) {
if (PFUser.currentUser() == nil) {
return
}
if (application.applicationState == UIApplicationState.Inactive || application.applicationState == UIApplicationState.Background) {
// Received the push notification when the app was in the background
PFAnalytics.trackAppOpenedWithRemoteNotificationPayload(userInfo)
// Inspect userInfo for the push notification payload
if let notificationPayloadTypeKey: String = userInfo["someKey"] as? String {
// Do something
}
} else {
// Received the push notification while the app is active
if let notificationPayloadTypeKey: String = userInfo["someKey"] as? String {
// Use NSNotificationCenter to inform your view to reload
NSNotificationCenter.defaultCenter().postNotificationName("loadMessages", object: nil)
}
}
}
Then you just need to add a listener inside of your view controller. Inside of viewDidLoad add the following which will call the function loadMessages whenever a notification is received.
NSNotificationCenter.defaultCenter().addObserver(self, selector: "loadMessages", name: "loadMessages", object: nil)
If you download the code for Parse's Anypic example project you can see how they handle remote notifications.
Related
I need to use the iOS 10 features in UNUserNotificationCenterDelegate. How can I implement this delegate in c# / Xamarin?
When using the an UNUserNotificationCenterDelegate, make sure that you assign it in the WillFinishLaunching or the FinishedLaunching methods in your app's UIApplicationDelegate.
You must assign your delegate object to the UNUserNotificationCenter object no later before your app finishes launching.
Ref: UNUserNotificationCenterDelegate
AppDelegate.cs Example
public override bool FinishedLaunching(UIApplication application, NSDictionary launchOptions)
{
UNUserNotificationCenter.Current.RequestAuthorization(UNAuthorizationOptions.Alert, (approved, err) =>
{
// Handle the user approval or refusal of your notifications...
});
UNUserNotificationCenter.Current.Delegate = new MyUNUserNotificationCenterDelegate();
return true;
}
In that example, I am creating/assigning a delegate class named MyUNUserNotificationCenterDelegate, so you need to implement that class.
MyUNUserNotificationCenterDelegate class example:
This UNUserNotificationCenterDelegate example will capture each local notification sent and toggle between showing it on the lock screen or outputting the details to the syslog.
public class MyUNUserNotificationCenterDelegate : UNUserNotificationCenterDelegate
{
bool toggle;
public override void WillPresentNotification(UNUserNotificationCenter center, UNNotification notification, Action<UNNotificationPresentationOptions> completionHandler)
{
if (toggle)
completionHandler(UNNotificationPresentationOptions.Alert);
else
{
Console.WriteLine(notification);
completionHandler(UNNotificationPresentationOptions.None);
}
toggle = !toggle;
}
}
Now you will actually need to send some notifications, this sets up a simple repeating notification:
Create/Schedule Local Notification:
// Schedule a repeating Notification...
var content = new UNMutableNotificationContent();
content.Title = new NSString("From SushiHangover");
content.Body = new NSString("StackOverflow rocks");
content.Sound = UNNotificationSound.Default;
var trigger = UNTimeIntervalNotificationTrigger.CreateTrigger(timeInterval: 60, repeats: true);
var request = UNNotificationRequest.FromIdentifier(identifier: "FiveSecond", content: content, trigger: trigger);
UNUserNotificationCenter.Current.AddNotificationRequest(request, (NSError error) =>
{
if (error != null) Console.WriteLine(error);
});
Every 60 seconds a notification is dispatched and if you are on the lock screen you will receive an alert every 120 seconds...
Recommend reading to understand how you Xamarin.iOS/C# to interact with delegates, protocols, and events:
iOS uses Objective-C delegates to implement the delegation pattern, in which one object passes work off to another. The object doing the work is the delegate of the first object. An object tells its delegate to do work by sending it messages after certain things happen. Sending a message like this in Objective-C is functionally equivalent to calling a method in C#. A delegate implements methods in response to these calls, and so provides functionality to the application.
Ref: Xamarin.iOS and Delegates
All the examples ask for authorization and start updating location in view controller. I want to set that in app delegate and in a view controller return a user's coordinates/location when pressing a button. (I want user coordinates/location accessible in any view controller)
You have few options here.
First of all, I would suggest you to implement or use already implemented wrapper for CLLocationManager and call it from anywhere in your code instead of implementing that functionality directly in your AppDelegate (example of such location manager implementation). Such location manager can communicate with the rest of your program using notification center (each view controller subscribe to specific notification which you define) or, for example, via an array of closures (each view controller pass its own closure for handling location update to the instance of location manager, and whenever a user location is updated, location manager calls each closure in the array hence all view controllers requested access to location data will receive that update).
Other than that, let's consider you already implemented access to user location through CLLocationManager in your AppDelegate. In a delegate function which receive updates about location (where you have actual location data), you can send this data to any view controller in your app by doing the following:
Swift - AppDelegate - using notification center
public func locationManager(manager: CLLocationManager,
didUpdateLocations locations: [CLLocation]) {
let arrayOfLocation = locations as NSArray
let location = arrayOfLocation.lastObject as! CLLocation
let coordLatLon = location.coordinate
var userInfo = [String:AnyObject]()
userInfo["longitude"] = coordLatLon.longitude
userInfo["latitude"] = coordLatLon.latitude
let nc = NSNotificationCenter.defaultCenter()
nc.postNotificationName("userLocationUpdate", object: self, userInfo: userInfo)
}
Swift - ViewController - using notification center (define that in viewDidAppear/viewDidLoad, for instance)
let nc = NSNotificationCenter.defaultCenter()
nc.addObserver(self, selector: #selector(ViewController.locationUpdated(_:)), name: "userLocationUpdate", object: nil)
Swift - ViewController - locationUpdated selector
func locationUpdated(notification: NSNotification) {
if let userInfo = notification.userInfo {
//access your data here
}
}
I want to store a Boolean which grants access to certain options when a user logs in with Parse, but when I log in and declare it to be true, the variable seems to remain false.
I tried using NSUserDefaults and storing a global variable.
This is where I log in on one view controller:
PFUser.logInWithUsernameInBackground(userName.text!, password: password.text!) {
(user: PFUser?, error: NSError?) -> Void in
if user != nil {
NSUserDefaults.standardUserDefaults().setBool(true, forKey: "accessGranted")
}
This functions fine and prints "Success" if I try.
On another view controller I have things like this:
addButton.enabled = NSUserDefaults.standardUserDefaults().boolForKey("accessGranted")
You can use NSUserDefaults to store your Bool globally this way:
Set your Bool this way:
NSUserDefaults.standardUserDefaults().setBool(false, forKey: "YourKey")
Then you can access it anywhere in your project this way:
let yourBool = NSUserDefaults.standardUserDefaults().boolForKey("YourKey")
Hope this will help.
NSUserDefaults:
Your are missing key component for it to work - you have to save the settings:
NSUserDefaults.standardUserDefaults().setBool(true, forKey: "accessGranted")
NSUserDefaults.standardUserDefaults().synchronize()
After that, your data that you stored will be stored to disk and you can access them anytime.
One-time assign to property:
After reading through comment, in order to access property only once, you can use something like this:
var accessGranted : Bool?
if accessGranted == nil {
accessGranted = yourValue
}
or as of Swift 2.0 (more on it here):
var accessGranted : Bool?
guard let granted = accessGranted else {
accessGranted = yourValue
}
Edit 2:
To notify second VC about changes, you can use multiple mechanisms (protocols / delegates etc.), but usually for this kind of message you would use Notifications (so your whole application can listen to that).
Notifications
You can use notifications like this:
In your "login" call, notify application that your access status changed, like this:
let NOTIFICATION_ACCESS_CHANGED_KEY = "NotificationAccessChanged"
NSNotificationCenter.defaultCenter().postNotificationName(NOTIFICATION_ACCESS_CHANGED)
then, everywhere where you are interested to listen to that change, put notification listener:
NSNotificationCenter.defaultCenter().addObserverForName(NOTIFICATION_ACCESS_CHANGED, object: nil, queue: nil) { (notification) -> Void in
// This block will be called when you post notification
self.doSomething()
}
Hope it helps!
I know that to register Parse.com push notifications I have to set it all in appdelegate file. But I am wondering if it is possible to override channels and register to multiple channels after user login in a viewcontroller class.
You should be able to by doing something like the following.
if(![currentInstallation channels]) {
[currentInstallation setChannels:#[#"WHATEVER1", #" WHATEVER2"]];
NSLog(#"Set Channel");
} else {
[currentInstall addUniqueObject:#"objectone" forKey:#"channels"];
[currentInstall addUniqueObject:#"objecttwo" forKey:#"channels"];
} [currentInstall saveInBackgroundWithBlock:(BOOL succeeded, NSError *error) {
if(!error){
NSLog(#"subscribed user to both channels");
} else {
NSLog(#"error subscribing to both channels: %#", error);
}
}];
All you have to do is run a shared instance of UIApplication anywhere in your application and then call the registration methods. Like this:
let application = UIApplication.sharedApplication()
let settings = UIUserNotificationSettings(forTypes: [.Alert, .Badge], categories: nil)
application.registerUserNotificationSettings(settings)
application.registerForRemoteNotifications()
This will present the push notifications dialog asking if they want to allow notifications and then make the call back to the appropriate app delegate method of either didFailToRegisterForRemoteNotificationsWithError or didRegisterForRemoteNotificationsWithDeviceToken
If you are testing on a simulator and not on an actual device didFailToRegisterForRemoteNotificationsWithError will always be called.
I've read Apple's Pasteboard Programming Guide, but it doesn't answer a particular question I have.
I'm trying to write a Cocoa application (for OS X, not iOS) that will keep track of everything that is written to the general pasteboard (so, whenever any application copies and pastes, but not, say, drags-and-drops, which also makes use of NSPasteboard). I could (almost) accomplish this by basically polling the general pasteboard on a background thread constantly, and checking changeCount. Of course, doing this would make me feel very dirty on the inside.
My question is, is there a way to ask the Pasteboard server to notify me through some sort of callback any time a change is made to the general pasteboard? I couldn't find anything in the NSPasteboard class reference, but I'm hoping it lurks somewhere else.
Another way I could imagine accomplishing this is if there was a way to swap out the general pasteboard implementation with a subclass of NSPasteboard that I could define myself to issue a callback. Maybe something like this is possible?
I would greatly prefer if this were possible with public, App Store-legal APIs, but if using a private API is necessary, I'll take that too.
Thanks!
Unfortunately the only available method is by polling (booo!). There are no notifications and there's nothing to observe for changed pasteboard contents. Check out Apple's ClipboardViewer sample code to see how they deal with inspecting the clipboard. Add a (hopefully not overzealous) timer to keep checking for differences and you've got a basic (if clunky) solution that should be App-Store-Friendly.
File an enhancement request at bugreporter.apple.com to request notifications or some other callback. Unfortunately it wouldn't help you until the next major OS release at the earliest but for now it's polling until we all ask them to give us something better.
There was once a post on a mailing list where the decision against a notification api was described. I can't find it right now though. The bottom line was that probably too many applications would register for that api even though they really wouldn't need to. If you then copy something the whole system goes through the new clipboard content like crazy, creating lots of work for the computer. So i don't think they'll change that behavior anytime soon. The whole NSPasteboard API is internally built around using the changeCount, too. So even your custom subclass of NSPasteboard would still have to keep polling.
If you really want to check if the pasteboard changed, just keep observing the changeCount very half second. Comparing integers is really fast so there's really no performance issue here.
Based on answer provided by Joshua I came up with similar implementation but in swift, here is the link to its gist: PasteboardWatcher.swift
Code snippet from same:
class PasteboardWatcher : NSObject {
// assigning a pasteboard object
private let pasteboard = NSPasteboard.generalPasteboard()
// to keep track of count of objects currently copied
// also helps in determining if a new object is copied
private var changeCount : Int
// used to perform polling to identify if url with desired kind is copied
private var timer: NSTimer?
// the delegate which will be notified when desired link is copied
weak var delegate: PasteboardWatcherDelegate?
// the kinds of files for which if url is copied the delegate is notified
private let fileKinds : [String]
/// initializer which should be used to initialize object of this class
/// - Parameter fileKinds: an array containing the desired file kinds
init(fileKinds: [String]) {
// assigning current pasteboard changeCount so that it can be compared later to identify changes
changeCount = pasteboard.changeCount
// assigning passed desired file kinds to respective instance variable
self.fileKinds = fileKinds
super.init()
}
/// starts polling to identify if url with desired kind is copied
/// - Note: uses an NSTimer for polling
func startPolling () {
// setup and start of timer
timer = NSTimer.scheduledTimerWithTimeInterval(2, target: self, selector: Selector("checkForChangesInPasteboard"), userInfo: nil, repeats: true)
}
/// method invoked continuously by timer
/// - Note: To keep this method as private I referred this answer at stackoverflow - [Swift - NSTimer does not invoke a private func as selector](http://stackoverflow.com/a/30947182/217586)
#objc private func checkForChangesInPasteboard() {
// check if there is any new item copied
// also check if kind of copied item is string
if let copiedString = pasteboard.stringForType(NSPasteboardTypeString) where pasteboard.changeCount != changeCount {
// obtain url from copied link if its path extension is one of the desired extensions
if let fileUrl = NSURL(string: copiedString) where self.fileKinds.contains(fileUrl.pathExtension!){
// invoke appropriate method on delegate
self.delegate?.newlyCopiedUrlObtained(copiedUrl: fileUrl)
}
// assign new change count to instance variable for later comparison
changeCount = pasteboard.changeCount
}
}
}
Note: in the shared code I am trying to identify if user has copied a
file url or not, the provided code can easily be modified for other general
purposes.
For those who need simplified version of code snippet that gets the job done in Swift 5.7,
it just works (base on #Devarshi code):
func watch(using closure: #escaping (_ copiedString: String) -> Void) {
let pasteboard = NSPasteboard.general
var changeCount = NSPasteboard.general.changeCount
Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { _ in
guard let copiedString = pasteboard.string(forType: .string),
pasteboard.changeCount != changeCount else { return }
defer {
changeCount = pasteboard.changeCount
}
closure(copiedString)
}
}
how to use is as below:
watch {
print("detected : \($0)")
}
then if you attempt copy any text in your pasteboard, it will watch and print out to the console like below..
detected : your copied message in pasteboard
detected : your copied message in pasteboard
in case, full code sample for how to use it for example in SwiftUI:
import SwiftUI
#main
struct TestApp: App {
var body: some Scene {
WindowGroup {
ContentView()
.onAppear {
watch {
print("detect : \($0)")
}
}
}
}
func watch(using closure: #escaping (_ copiedString: String) -> Void) {
let pasteboard = NSPasteboard.general
var changeCount = NSPasteboard.general.changeCount
Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { _ in
guard let copiedString = pasteboard.string(forType: .string),
pasteboard.changeCount != changeCount else { return }
defer {
changeCount = pasteboard.changeCount
}
closure(copiedString)
}
}
}
It's not necessary to poll. Pasteboard would generally only be changed by the current view is inactive or does not have focus. Pasteboard has a counter that is incremented when contents change. When window regains focus (windowDidBecomeKey), check if changeCount has changed then process accordingly.
This does not capture every change, but lets your application respond if the Pasteboard is different when it becomes active.
In Swift...
var pasteboardChangeCount = NSPasteboard.general().changeCount
func windowDidBecomeKey(_ notification: Notification)
{ Swift.print("windowDidBecomeKey")
if pasteboardChangeCount != NSPasteboard.general().changeCount
{ viewController.checkPasteboard()
pasteboardChangeCount = NSPasteboard.general().changeCount
}
}
I have a solution for more strict case: detecting when your content in NSPasteboard was replaced by something else.
If you create a class that conforms to NSPasteboardWriting and pass it to -writeObjects: along with the actual content, NSPasteboard will retain this object until its content is replaced. If there are no other strong references to this object, it get deallocated.
Deallocation of this object is the moment when new NSPasteboard got new content.