This question already has answers here:
NSTimer not firing
(3 answers)
Closed 7 years ago.
I've been trying to get variations of this code to run, but countItems() never prints out the NSLog. Can someone tell me what is wrong?
func someFunction() {
var fireDate = NSDate(timeIntervalSinceNow: 5)
someTimer = NSTimer(fireDate: fireDate, interval: 120, target: self, selector: "countItems", userInfo: nil, repeats: true)
}
func countItems() {
NSLog("countItems")
//Perform some code here...
}
Try reading the docs! It's all right there. You have created the timer but you have never scheduled it on a run loop. So it does nothing. The docs clearly say:
You must add the new timer to a run loop, using addTimer:forMode:.
Well, you don't.
You might be happier like this:
NSTimer.scheduledTimerWithTimeInterval(
120, target: self, selector: "countItems", userInfo:nil, repeats:true)
Add fire():
func someFunction() {
var fireDate = NSDate(timeIntervalSinceNow: 5)
someTimer = NSTimer(fireDate: fireDate, interval: 120, target: self, selector: "countItems", userInfo: nil, repeats: true)
someTimer.fire()
}
Or it wont start: Documentation
Related
This question already has answers here:
How can I use Timer (formerly NSTimer) in Swift?
(16 answers)
Closed 4 years ago.
I am quite new to Swift and would love to know how to create a loop that runs some code every 30 seconds? I feel as though it is a basic question but I can't really find what I'm looking for.
You can make Use of Timer
Timer.scheduledTimerWithTimeInterval(0.30, target: self, selector: #selector(timerFired), userInfo: userInfo, repeats: true)
timerFired: is the method that gets called after interval
#objc func timerFired() {
print("Timer Called with interval 30seconds")
}
You need to use scheduled timer. In viewDidLoad()
Timer.scheduledTimer(timeInterval: 30, target: self, selector: #selector(YourFuncName), userInfo: nil, repeats: true)
and func for selector
#objc func YourFuncName() {
print("every 30seconds")
}
func startTimer() {
timer = Timer.scheduledTimer(timeInterval: 30, target: self, selector: #selector(UpdateTimer), userInfo: nil, repeats: true)
}
#objc func UpdateTimer() {
counter += 1
}
to start
startTimer();
and to stop
timer.invalidate()
I want to call the method func adjustmentBestSongBpmHeartRate() every 1.1 second. I used Timer, but it doesn't work. I have read the document and found a lot of sample code, it still does work! Is there anything I missed?
timer = Timer.scheduledTimer(timeInterval: 1.1, target: self, selector: #selector(self.adjustmentBestSongBpmHeartRate), userInfo: nil, repeats: false)
timer.fire()
func adjustmentBestSongBpmHeartRate() {
print("frr")
}
I found that creating the timer in an OperationQueue Operation did not work. I assume this is because there is no runloop.
Therefore, the following code fixed my problem:
DispatchQueue.main.async {
// timer needs a runloop?
self.timeoutTimer = Timer.scheduledTimer(timeInterval: self.timeout, target: self, selector: #selector(self.onTimeout(_:)), userInfo: nil, repeats: false)
}
Timer methods with a selector are supposed to have one parameter: The timer itself. Thus your code should really look like this: 1
Timer.scheduledTimer(timeInterval: 1.1,
target: self,
selector: #selector(self.adjustmentBestSongBpmHeartRate(_:),
userInfo: nil,
repeats: false)
#objc func adjustmentBestSongBpmHeartRate(_ timer: Timer) {
print("frr")
}
Note that if your app only runs on iOS >= 10, you can use the new method that takes a block to invoke rather than a target/selector. Much cleaner and more type-safe:
class func scheduledTimer(withTimeInterval interval: TimeInterval,
repeats: Bool,
block: #escaping (Timer) -> Void) -> Timer
That code would look like this:
timer = Timer.scheduledTimer(withTimeInterval: 1.1,
repeats: false) {
timer in
//Put the code that be called by the timer here.
print("frr")
}
Note that if your timer block/closure needs access to instance variables from your class you have to take special care with self. Here's a good pattern for that sort of code:
timer = Timer.scheduledTimer(withTimeInterval: 1.1,
repeats: false) {
//"[weak self]" creates a "capture group" for timer
[weak self] timer in
//Add a guard statement to bail out of the timer code
//if the object has been freed.
guard let strongSelf = self else {
return
}
//Put the code that be called by the timer here.
print(strongSelf.someProperty)
strongSelf.someOtherProperty = someValue
}
Edit (updated 15 December)
1: I should add that the method you use in the selector has to use Objective-C dynamic dispatch. In Swift 4 and later, the individual methods you reference must be tagged with the #objc tag. In previous versions of Swift you could also declare the entire class that defines the selector with the #objc qualifier, or you could make the class that defined the selector a subclass of NSObject or any class that inherits from NSOBject. (It's quite common to define the method the timer calls inside a UIViewController, which is a subclass of NSObject, so it used to "just work".
Swift 3
In my case it worked after I added to my method the #obj prefix
Class TestClass {
private var timer: Timer?
func start() {
guard timer == nil else { return }
timer = Timer.scheduledTimer(timeInterval: 60, target: self, selector: #selector(handleMyFunction), userInfo: nil, repeats: false)
}
func stop() {
guard timer != nil else { return }
timer?.invalidate()
timer = nil
}
#objc func handleMyFunction() {
// Code here
}
}
Try this -
if #available(iOS 10.0, *) {
self.timer = Timer.scheduledTimer(withTimeInterval: 0.2, repeats: false, block: { _ in
self.update()
})
} else {
self.timer = Timer.scheduledTimer(timeInterval: 0.2, target: self, selector: #selector(self.update), userInfo: nil, repeats: false)
}
Mostly the problem must have been because of iOS version of mobile.
Swift 5, Swift 4 Simple way only call with Dispatch Queue Async
DispatchQueue.main.async
{
self.andicator.stopAnimating()
self.bgv.isHidden = true
Timer.scheduledTimer(withTimeInterval: 1.0, repeats: false, block: { _ in
obj.showAlert(title: "Successfully!", message: "Video save successfully to Library directory.", viewController: self)
})
}
I have solved the question asked by myself.
I'm using apple watch to control my iphone app.
I try to press a button on apple watch to present a new viewcontroller on iphone.
When I write Timer in override func viewDidLoad(), Timer doesn't work. I move Timer to override func viewWillAppear() it works.
I think maybe there's something wrong with controlling by apple watch
I found that if you try to initialize the timer directly at the class-level, it won't work if you're targeting a selector in that same class. When it fires, it can't find the selector.
To get around this, I only initialize the timer after the object containing the selector has been initialized. If it's in the same class, put the initialization code in the ViewDidLoad or similar. Just not in the initializer. Then it will work. No dispatch queue needed.
Also, you do not need to use a selector that accepts the timer as a parameter. You can, but contrary to the answer with a ton of votes, that's not actually true, or more specifically, it works fine for me without it, just as you have it without it.
By the way, I think the reason the dispatch queue worked is because you're forcing the timer to be created after the object was initializing, confirming my above statement.
let timer:Timer?
override func viewDidLoad(){
super.viewDidLoad()
timer = Timer.scheduledTimer(timeInterval: 1.1, target: self, selector: #selector(adjustmentBestSongBpmHeartRate), userInfo: nil, repeats: false)
timer.fire()
}
func adjustmentBestSongBpmHeartRate() {
print("frr")
}
Note: This is code typed from memory, not copied from Xcode so it may not compile, but hopefully you get the idea.
Swift3
var timer = Timer()
timer = Timer.scheduledTimer(timeInterval: 5, target: self, selector: #selector(self.compruebaConexion), userInfo: nil, repeats: true)
my two cents.
I read about "didLoad" and when invoking it.
so we can use a delay:
class ViewController: UIViewController {
var timer: Timer?
override func viewDidLoad() {
super.viewDidLoad()
startTimer()
}
final func killTimer(){
self.timer?.invalidate()
self.timer = nil
}
final private func startTimer() {
// make it re-entrant:
// if timer is running, kill it and start from scratch
self.killTimer()
let fire = Date().addingTimeInterval(1)
let deltaT : TimeInterval = 1.0
self.timer = Timer(fire: fire, interval: deltaT, repeats: true, block: { (t: Timer) in
print("hello")
})
RunLoop.main.add(self.timer!, forMode: RunLoopMode.commonModes)
}
I have this problem for a few days now and I don't get what I am doing wrong.
My application is basically just creating some timers. I need to stop them and create new ones. But at the moment stopping them doesn't work.
self.timer = NSTimer.scheduledTimerWithTimeInterval(timeInterval, target:self, selector: "timerDidEnd:", userInfo: "Notification fired", repeats: false)
That's my timer
func timerDidEnd(timer:NSTimer){
createUnrepeatedAlarmWithUpdateInterval()
}
Because my timer didn't want to stop I am currently using the unrepeated timer and start it myself after it stopped.
func stopAlarm() {
if self.timer != nil {
self.timer!.invalidate()
}
self.timer = nil
self.timer = NSTimer()
}
And that's how I stop my timer.
alarmManager.stopAlarm()
alarmManager.createUnrepeatedAlarmWithUpdateInterval()
I call the stopAlarm() function before creating a new timer.
I really don't know what I am doing wrong so I appreciate every answer :)
class AlarmManager: ViewController{
private var timer : NSTimer?
private var unrepeatedTimer : NSTimer?
private let notificationManager = NotificationManager()
private var current = NSThread()
private let settingsViewController = SettingsViewController()
func createRepeatedAlarmWithUpdateInterval(){
var timeInterval:NSTimeInterval = settingsViewController.getUpdateIntervalSettings()
if timer == nil{
timer = NSTimer.scheduledTimerWithTimeInterval(timeInterval,
target: self,
selector: "repeatedTimerDidEnd:",
userInfo: "Notification fired",
repeats: true)
}
}
func repeatedTimerDidEnd(repeatedTimer:NSTimer){
ConnectionManager.sharedInstance.loadTrainings(settingsViewController.getServerSettings())
createUnrepeatedAlarm(10)
}
func createUnrepeatedAlarm(timeInterval:Double){
unrepeatedTimer = NSTimer.scheduledTimerWithTimeInterval(timeInterval,
target: self,
selector: "unrepeatedTimerDidEnd:",
userInfo: "Notification fired",
repeats: false)
}
func unrepeatedTimerDidEnd(unrepeatedTimer:NSTimer){
notificationManager.createNotification(self, reminderType: NotificationManager.ITEMRATINGREMINDER)
notificationManager.createNotification(self, reminderType: NotificationManager.ITEMREMINDER)
print("UnrepeatedAlarm ended")
}
func stopAlarm(){
print("StopAlarm triggered")
if (timer != nil)
{
print("stoptimer executed")
timer!.invalidate()
timer = nil
}
if (unrepeatedTimer != nil)
{
unrepeatedTimer!.invalidate()
unrepeatedTimer = nil
}
}
}
Thats the whole code of this class. Maybe that helps :D
The usual way to start and stop a timer safely is
var timer : Timer?
func startTimer()
{
if timer == nil {
timer = Timer.scheduledTimer(timeInterval: timeInterval, target: self, selector: #selector(timerFired), userInfo: nil, repeats: true)
}
}
func stopTimer()
{
timer?.invalidate()
timer = nil
}
startTimer() starts the timer only if it's nil and stopTimer() stops it only if it's not nil.
You have only to take care of stopping the timer before creating/starting a new one.
Make sure you're calling invalidate on the same thread as the timer.
From the documentation:
Special Considerations
You must send this message from the thread on which the timer was installed. If you send this message from another thread, the input source associated with the timer may not be removed from its run loop, which could prevent the thread from exiting properly.
https://developer.apple.com/documentation/foundation/nstimer/1415405-invalidate?language=objc
Something that's not really covered by the previous answers is that you should be careful your timer isn't scheduled multiple times.
If you schedule a timer multiple times without first invalidating it, it'll end up scheduled on multiple run loops, and invalidating it then becomes nigh impossible.
For me, it happened when calling my scheduleTimer() function in separate functions in my view controller's life cycle (viewWillAppear, viewDidAppear, ...)
So in short, if you aren't sure (or you cannot guarantee) your Timer is only scheduled once, just always invalidate it first.
I have tried every possible solution found but not able to resolve that at the end I have set repeat "false" while initialising timer like below
self.timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(viewcontroller.methodname), userInfo: nil, repeats: false)
And need to add above line in my selector method for whatever the condition for which I wanted to repeat the time.
For example:-
My requirement is I want to repeatedly call some method until one condition satisfied. So instead of adding repeats true I set it false as repeat true does not invalidate timer in my case.
I have added below in my viewdidload method
self.timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(viewcontroller.method), userInfo: nil, repeats: false)
in selector function I added below code
#objc func method{
if condition not matched{
self.timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(viewcontroller.method), userInfo: nil, repeats: false)
}
else{
// once you are here your timer invalidate automatically
}
}
Hope this will solve your problem
For Swift 5 Xcode 12.4 there is example to use timer:
class MyController: UIViewController {
private id: Float;
func setValue(_ value: Float, withAnimation: Bool) {
let step: Float = value / 200
var current: Float = withAnimation ? 0.0 : value
let _ = Timer.scheduledTimer(withTimeInterval: 0.01, repeats: withAnimation) { timer in
DispatchQueue.main.async {
self.id = current
current += step
if current > value || withAnimation == false {
self.id = current
timer.invalidate()
}
}
}
}
}
Say I had a function, any function, that I wanted to run for only three seconds and then never run again. How would I do this? Would I use NSTimer? Thank you for your help.
Here you go,
NSTimer.scheduledTimerWithTimeInterval(3, target: self, selector: Selector("updateProgress:"), userInfo: nil, repeats: false)
func updateProgress(timer: NSTimer){
}
I'm trying to use an NSTimer in my app, and was wondering if it's possible to call two methods when the timer fires.
Here's the code:
gameTimer = NSTimer.scheduledTimerWithTimeInterval(0.01, target: self, selector:
Selector("gameMovement" && "fireBullet"), userInfo: nil, repeats: true)
I'm getting an error saying there are two arguments in the Selector.
Nope. You would call just one method that delegates to all the things you want.
func someFunc() {
gameTimer = NSTimer.scheduledTimerWithTimeInterval(
0.01,
target: self,
selector: Selector("timerFired"),
userInfo: nil,
repeats: true
)
}
func timerFired() {
gameMovement()
fireBullet()
}
This is a more maintainable pattern anyway, as it's easier to see how your code flows.