How to run function whenever the app appears on screen in swift?
I have a function which I want to run whenever the app appears on screen.
I tried all these methods:
override func viewWillAppear() {
generateRandomNumber()
}
override func viewDidAppear() {
generateRandomNumber()
}
override func viewDidLoad() {
generateRandomNumber()
}
Although the function runs every time I run app, but if after running app I press home botton and come back to app (didn't terminated the app) then the function does not execute again.
Update: I tried using following code in my ViewController:
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self, selector: #selector(applicationDidBecomeActive), name: UIApplication.didBecomeActiveNotification, object: nil)
}
@objc func applicationDidBecomeActive(notification: NSNotification) {
generateRandomNumber()
}
But it takes about a second to run. Is there a better way?
ios swift uiviewcontroller
edited Jan 20 at 16:52
rmaddy
242k27316380
asked Jan 20 at 14:22
ocean hancockocean hancock
607
add a comment |
I have a function which I want to run whenever the app appears on screen.
I tried all these methods:
override func viewWillAppear() {
generateRandomNumber()
}
override func viewDidAppear() {
generateRandomNumber()
}
override func viewDidLoad() {
generateRandomNumber()
}
Although the function runs every time I run app, but if after running app I press home botton and come back to app (didn't terminated the app) then the function does not execute again.
Update: I tried using following code in my ViewController:
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self, selector: #selector(applicationDidBecomeActive), name: UIApplication.didBecomeActiveNotification, object: nil)
}
@objc func applicationDidBecomeActive(notification: NSNotification) {
generateRandomNumber()
}
But it takes about a second to run. Is there a better way?
ios swift uiviewcontroller
edited Jan 20 at 16:52
rmaddy
242k27316380
asked Jan 20 at 14:22
ocean hancockocean hancock
607
2
appwillEnterForeground in appdelegate.
– Gagan_iOS
Jan 20 at 14:32
1
Your updated code looks fine. I suspect when you say "it takes about a second to run" that you're measuring at the wrong point. Put a breakpoint inapplicationDidBecomeActive, or add a print statement. I suspect it runs much sooner than you think and that you're probably not updating your views to match.
– Rob Napier
Jan 20 at 15:26
will it be even more faster if I useapplicationWillEnterForeground?
– ocean hancock
Jan 20 at 15:28
1
That happens slightly before "active," but it should be nowhere near 1 second. It really has to do with whether you want system alerts, incoming phone calls and the like to trigger it. It's not about performance.
– Rob Napier
Jan 20 at 15:40
I was trying to just replaceapplicationDidBecomeActivewithapplicationWillEnterForegroundin the updated code above but it didn't work. can you please show me how to useapplicationWillEnterForegroundin ViewController.swift?
– ocean hancock
Jan 20 at 15:46
add a comment |
I have a function which I want to run whenever the app appears on screen.
I tried all these methods:
override func viewWillAppear() {
generateRandomNumber()
}
override func viewDidAppear() {
generateRandomNumber()
}
override func viewDidLoad() {
generateRandomNumber()
}
Although the function runs every time I run app, but if after running app I press home botton and come back to app (didn't terminated the app) then the function does not execute again.
Update: I tried using following code in my ViewController:
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self, selector: #selector(applicationDidBecomeActive), name: UIApplication.didBecomeActiveNotification, object: nil)
}
@objc func applicationDidBecomeActive(notification: NSNotification) {
generateRandomNumber()
}
But it takes about a second to run. Is there a better way?
ios swift uiviewcontroller
edited Jan 20 at 16:52
rmaddy
242k27316380
asked Jan 20 at 14:22
ocean hancockocean hancock
607
I have a function which I want to run whenever the app appears on screen.
I tried all these methods:
override func viewWillAppear() {
generateRandomNumber()
}
override func viewDidAppear() {
generateRandomNumber()
}
override func viewDidLoad() {
generateRandomNumber()
}
Although the function runs every time I run app, but if after running app I press home botton and come back to app (didn't terminated the app) then the function does not execute again.
Update: I tried using following code in my ViewController:
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self, selector: #selector(applicationDidBecomeActive), name: UIApplication.didBecomeActiveNotification, object: nil)
}
@objc func applicationDidBecomeActive(notification: NSNotification) {
generateRandomNumber()
}
But it takes about a second to run. Is there a better way?
ios swift uiviewcontroller
ios swift uiviewcontroller
edited Jan 20 at 16:52
rmaddy
242k27316380
asked Jan 20 at 14:22
ocean hancockocean hancock
607
edited Jan 20 at 16:52
rmaddy
242k27316380
asked Jan 20 at 14:22
ocean hancockocean hancock
607
edited Jan 20 at 16:52
rmaddy
242k27316380
edited Jan 20 at 16:52
rmaddy
242k27316380
edited Jan 20 at 16:52
rmaddy
242k27316380
242k27316380
asked Jan 20 at 14:22
ocean hancockocean hancock
607
asked Jan 20 at 14:22
ocean hancockocean hancock
607
asked Jan 20 at 14:22
ocean hancockocean hancock
607
607
2
appwillEnterForeground in appdelegate.
– Gagan_iOS
Jan 20 at 14:32
1
Your updated code looks fine. I suspect when you say "it takes about a second to run" that you're measuring at the wrong point. Put a breakpoint inapplicationDidBecomeActive, or add a print statement. I suspect it runs much sooner than you think and that you're probably not updating your views to match.
– Rob Napier
Jan 20 at 15:26
will it be even more faster if I useapplicationWillEnterForeground?
– ocean hancock
Jan 20 at 15:28
1
That happens slightly before "active," but it should be nowhere near 1 second. It really has to do with whether you want system alerts, incoming phone calls and the like to trigger it. It's not about performance.
– Rob Napier
Jan 20 at 15:40
I was trying to just replaceapplicationDidBecomeActivewithapplicationWillEnterForegroundin the updated code above but it didn't work. can you please show me how to useapplicationWillEnterForegroundin ViewController.swift?
– ocean hancock
Jan 20 at 15:46
add a comment |
2
appwillEnterForeground in appdelegate.
– Gagan_iOS
Jan 20 at 14:32
1
Your updated code looks fine. I suspect when you say "it takes about a second to run" that you're measuring at the wrong point. Put a breakpoint inapplicationDidBecomeActive, or add a print statement. I suspect it runs much sooner than you think and that you're probably not updating your views to match.
– Rob Napier
Jan 20 at 15:26
will it be even more faster if I useapplicationWillEnterForeground?
– ocean hancock
Jan 20 at 15:28
1
That happens slightly before "active," but it should be nowhere near 1 second. It really has to do with whether you want system alerts, incoming phone calls and the like to trigger it. It's not about performance.
– Rob Napier
Jan 20 at 15:40
I was trying to just replaceapplicationDidBecomeActivewithapplicationWillEnterForegroundin the updated code above but it didn't work. can you please show me how to useapplicationWillEnterForegroundin ViewController.swift?
– ocean hancock
Jan 20 at 15:46
2
2
appwillEnterForeground in appdelegate.
– Gagan_iOS
Jan 20 at 14:32
appwillEnterForeground in appdelegate.
– Gagan_iOS
Jan 20 at 14:32
1
1
Your updated code looks fine. I suspect when you say "it takes about a second to run" that you're measuring at the wrong point. Put a breakpoint in
applicationDidBecomeActive, or add a print statement. I suspect it runs much sooner than you think and that you're probably not updating your views to match.– Rob Napier
Jan 20 at 15:26
Your updated code looks fine. I suspect when you say "it takes about a second to run" that you're measuring at the wrong point. Put a breakpoint in
applicationDidBecomeActive, or add a print statement. I suspect it runs much sooner than you think and that you're probably not updating your views to match.– Rob Napier
Jan 20 at 15:26
will it be even more faster if I use
applicationWillEnterForeground?– ocean hancock
Jan 20 at 15:28
will it be even more faster if I use
applicationWillEnterForeground?– ocean hancock
Jan 20 at 15:28
1
1
That happens slightly before "active," but it should be nowhere near 1 second. It really has to do with whether you want system alerts, incoming phone calls and the like to trigger it. It's not about performance.
– Rob Napier
Jan 20 at 15:40
That happens slightly before "active," but it should be nowhere near 1 second. It really has to do with whether you want system alerts, incoming phone calls and the like to trigger it. It's not about performance.
– Rob Napier
Jan 20 at 15:40
I was trying to just replace
applicationDidBecomeActive with applicationWillEnterForeground in the updated code above but it didn't work. can you please show me how to use applicationWillEnterForeground in ViewController.swift?– ocean hancock
Jan 20 at 15:46
I was trying to just replace
applicationDidBecomeActive with applicationWillEnterForeground in the updated code above but it didn't work. can you please show me how to use applicationWillEnterForeground in ViewController.swift?– ocean hancock
Jan 20 at 15:46
add a comment |
1 Answer
1
active
oldest
votes
In your application delegate, you want to implement applicationDidBecomeActive. Note that this will also run when things like system alerts are dismissed. If you only want to run something when returning from the background, you want applicationWillEnterForeground. For full details, see "Managing State Transitions" in the UIApplicationDelegate documentation and Strategies for Handling App State Transitions in the App Programming Guide.
Your approach looks basically right; in order to use willEnterForeground rather than didBecomeActive, it's just a small change:
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self,
selector: #selector(applicationWillEnterForeground),
name: UIApplication.willEnterForegroundNotification,
object: nil)
}
@objc func applicationWillEnterForeground(notification: Notification) {
generateRandomNumber()
}
The only thing to be careful with here is that this observer continues to be in force as long as the view controller exists, even if it's not currently on the screen (the most common case of that is when it's presented other view controllers). In some cases that's a problem, and you should call addObserver in viewWillAppear and removeObserver in viewDidDisappear instead of using viewDidLoad.
answered Jan 20 at 14:25
Rob NapierRob Napier
202k28298424
1
I am new to swift and having a little difficulty understanding apple documentation. Can you please tell me when should I right my generateRandomNumber() function. generateRandomNumber() is located in ViewController.swift
– ocean hancock
Jan 20 at 14:36
add a comment |
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In your application delegate, you want to implement applicationDidBecomeActive. Note that this will also run when things like system alerts are dismissed. If you only want to run something when returning from the background, you want applicationWillEnterForeground. For full details, see "Managing State Transitions" in the UIApplicationDelegate documentation and Strategies for Handling App State Transitions in the App Programming Guide.
Your approach looks basically right; in order to use willEnterForeground rather than didBecomeActive, it's just a small change:
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self,
selector: #selector(applicationWillEnterForeground),
name: UIApplication.willEnterForegroundNotification,
object: nil)
}
@objc func applicationWillEnterForeground(notification: Notification) {
generateRandomNumber()
}
The only thing to be careful with here is that this observer continues to be in force as long as the view controller exists, even if it's not currently on the screen (the most common case of that is when it's presented other view controllers). In some cases that's a problem, and you should call addObserver in viewWillAppear and removeObserver in viewDidDisappear instead of using viewDidLoad.
answered Jan 20 at 14:25
Rob NapierRob Napier
202k28298424
1
I am new to swift and having a little difficulty understanding apple documentation. Can you please tell me when should I right my generateRandomNumber() function. generateRandomNumber() is located in ViewController.swift
– ocean hancock
Jan 20 at 14:36
add a comment |
In your application delegate, you want to implement applicationDidBecomeActive. Note that this will also run when things like system alerts are dismissed. If you only want to run something when returning from the background, you want applicationWillEnterForeground. For full details, see "Managing State Transitions" in the UIApplicationDelegate documentation and Strategies for Handling App State Transitions in the App Programming Guide.
Your approach looks basically right; in order to use willEnterForeground rather than didBecomeActive, it's just a small change:
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self,
selector: #selector(applicationWillEnterForeground),
name: UIApplication.willEnterForegroundNotification,
object: nil)
}
@objc func applicationWillEnterForeground(notification: Notification) {
generateRandomNumber()
}
The only thing to be careful with here is that this observer continues to be in force as long as the view controller exists, even if it's not currently on the screen (the most common case of that is when it's presented other view controllers). In some cases that's a problem, and you should call addObserver in viewWillAppear and removeObserver in viewDidDisappear instead of using viewDidLoad.
answered Jan 20 at 14:25
Rob NapierRob Napier
202k28298424
1
I am new to swift and having a little difficulty understanding apple documentation. Can you please tell me when should I right my generateRandomNumber() function. generateRandomNumber() is located in ViewController.swift
– ocean hancock
Jan 20 at 14:36
add a comment |
In your application delegate, you want to implement applicationDidBecomeActive. Note that this will also run when things like system alerts are dismissed. If you only want to run something when returning from the background, you want applicationWillEnterForeground. For full details, see "Managing State Transitions" in the UIApplicationDelegate documentation and Strategies for Handling App State Transitions in the App Programming Guide.
Your approach looks basically right; in order to use willEnterForeground rather than didBecomeActive, it's just a small change:
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self,
selector: #selector(applicationWillEnterForeground),
name: UIApplication.willEnterForegroundNotification,
object: nil)
}
@objc func applicationWillEnterForeground(notification: Notification) {
generateRandomNumber()
}
The only thing to be careful with here is that this observer continues to be in force as long as the view controller exists, even if it's not currently on the screen (the most common case of that is when it's presented other view controllers). In some cases that's a problem, and you should call addObserver in viewWillAppear and removeObserver in viewDidDisappear instead of using viewDidLoad.
answered Jan 20 at 14:25
Rob NapierRob Napier
202k28298424
In your application delegate, you want to implement applicationDidBecomeActive. Note that this will also run when things like system alerts are dismissed. If you only want to run something when returning from the background, you want applicationWillEnterForeground. For full details, see "Managing State Transitions" in the UIApplicationDelegate documentation and Strategies for Handling App State Transitions in the App Programming Guide.
Your approach looks basically right; in order to use willEnterForeground rather than didBecomeActive, it's just a small change:
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self,
selector: #selector(applicationWillEnterForeground),
name: UIApplication.willEnterForegroundNotification,
object: nil)
}
@objc func applicationWillEnterForeground(notification: Notification) {
generateRandomNumber()
}
The only thing to be careful with here is that this observer continues to be in force as long as the view controller exists, even if it's not currently on the screen (the most common case of that is when it's presented other view controllers). In some cases that's a problem, and you should call addObserver in viewWillAppear and removeObserver in viewDidDisappear instead of using viewDidLoad.
answered Jan 20 at 14:25
Rob NapierRob Napier
202k28298424
edited Jan 20 at 16:25
answered Jan 20 at 14:25
Rob NapierRob Napier
202k28298424
answered Jan 20 at 14:25
Rob NapierRob Napier
202k28298424
answered Jan 20 at 14:25
Rob NapierRob Napier
202k28298424
202k28298424
1
I am new to swift and having a little difficulty understanding apple documentation. Can you please tell me when should I right my generateRandomNumber() function. generateRandomNumber() is located in ViewController.swift
– ocean hancock
Jan 20 at 14:36
add a comment |
1
I am new to swift and having a little difficulty understanding apple documentation. Can you please tell me when should I right my generateRandomNumber() function. generateRandomNumber() is located in ViewController.swift
– ocean hancock
Jan 20 at 14:36
1
1
I am new to swift and having a little difficulty understanding apple documentation. Can you please tell me when should I right my generateRandomNumber() function. generateRandomNumber() is located in ViewController.swift
– ocean hancock
Jan 20 at 14:36
I am new to swift and having a little difficulty understanding apple documentation. Can you please tell me when should I right my generateRandomNumber() function. generateRandomNumber() is located in ViewController.swift
– ocean hancock
Jan 20 at 14:36
add a comment |
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2
appwillEnterForeground in appdelegate.
– Gagan_iOS
Jan 20 at 14:32
1
Your updated code looks fine. I suspect when you say "it takes about a second to run" that you're measuring at the wrong point. Put a breakpoint in
applicationDidBecomeActive, or add a print statement. I suspect it runs much sooner than you think and that you're probably not updating your views to match.– Rob Napier
Jan 20 at 15:26
will it be even more faster if I use
applicationWillEnterForeground?– ocean hancock
Jan 20 at 15:28
1
That happens slightly before "active," but it should be nowhere near 1 second. It really has to do with whether you want system alerts, incoming phone calls and the like to trigger it. It's not about performance.
– Rob Napier
Jan 20 at 15:40
I was trying to just replace
applicationDidBecomeActivewithapplicationWillEnterForegroundin the updated code above but it didn't work. can you please show me how to useapplicationWillEnterForegroundin ViewController.swift?– ocean hancock
Jan 20 at 15:46