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I am starting timer inside ParentView class. On some button click I stop timer and if needed start that again. This works fine. However, if perform those button clicks quickly I see there will be couple of timer instances which keeps firing target scheduledTask method.
class MyTimer {
weak var delegate: ParentViewDelegate?
private var timer: Timer?
func start() {
timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(scheduledTask), userInfo: nil, repeats: true)
timer?.fire()
}
#objc private func scheduledTask() {
print("timer call this per seconds")
}
func stop() {
timer?.invalidate()
timer = nil
}
final class VideoPlayerContainer: UIView {
// MARK: - Properties
private var mytimer: Mytimer? = Mytimer()
}
How should I make sure there will be always only once instance of timer and stop actions kills that timer present in parentView?
Simply check if there is already a timer before you start a new one;
func start() {
guard timer == nil else {
return
}
timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(scheduledTask), userInfo: nil, repeats: true)
timer?.fire()
}
Alternatively, invalidate any existing timer before you start the new one;
func start() {
timer?.invalidate()
timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(scheduledTask), userInfo: nil, repeats: true)
timer?.fire()
}
This question already has answers here:
Why would a `scheduledTimer` fire properly when setup outside a block, but not within a block?
(3 answers)
Closed 6 years ago.
I've been trying to utilize Timer in Swift and I've simplified it town to the following:
func startTimer () {
timer = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(ViewController.test), userInfo: nil, repeats: true)
}
func test () {
print("FIRED")
}
I would like to call this from another function and have verified the startTimer function works, but the timer doesn't fire. Does this have something to do with the RunLoop? I'm fairly new to coding so any explanation would be appreciated.
Good Practice: In startTimer() check that the timer has not already been created and make the assignment. In stopTimer() check that the timer exists before calling invalidate, and set the timer back to nil.
Also, for your selector make sure you have the #objc prefix. You should be able to get a working timer with the code provided. Happy coding!
class SomeClass {
var timer: Timer?
func startTimer() {
guard timer == nil else { return }
timer = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(test), userInfo: nil, repeats: true)
}
func stopTimer() {
guard timer != nil else { return }
timer?.invalidate()
timer = nil
}
#objc func test() {
}
}
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)
}
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
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.