When application comes to foreground from background then appixationDidBecomeActive gets called. Now, I want to refresh the page from which the home button was tapped. In which method I can write the refresh code. viewWillAppear is not getting called.
In this case viewWillAppear never gets called, you can fire notification(s) whenever -(void)applicationWillEnterForeground:(UIApplication *)application gets called and use it on the view you want.
You can use custom notification like : NSNotificationCenter.
And on call of this you can refresh your view.
Related
I have a timer with a countdown. In recent testing, I've noticed that if I hit the home button and return to the app, the timer is off (fewer seconds have ticked off than should).
I've noticed in testing that ViewDid and ViewWill Appear do not fire when re-opening the app. I know that:
- (void)applicationWillEnterForeground:(UIApplication *)application
Fires, but how do I make it specific to certain part of a viewController that was active?
You probably want applicationDidBecomeActive: and applicationWillResignActive:, which are sent to your app delegate. There are also notifications posted (e.g. UIApplicationDidBecomeActiveNotification) you could listen for.
Those are also posted when, e.g., a system alert comes in. If you just want to be told when you're going to the background, try applicationDidEnterBackground: and applicationWillEnterForeground:
See the Apple Docs on lifecycle for details.
Just for the sake of follow up, as the question was answered above.
I had the exact same problem as Eric and then I implemented Jesse's suggestion about using applicationDidBecomeActive: on the delegate. I just wanted to make sure how all the different methods were being called, and I found this:
application:didFinishLaunchingWithOptions: is called at the very start, as expected.
Then, is the main view controller's viewDidLoad turn.
Then viewWillAppear: is called.
Back in the application delegate, applicationDidBecomeActive: is triggered (here I call my reactivateTimer method which I implemented in the main view controller).
The reactivateTimer method is executed.
The last step is the call to the main view controller's viewDidAppear:
I have a problem that the ViewWillAppear method for a UIView does not fire when the application returns from the background. This is a problem, as my main application screen is showing values that are retrieved from the user settings, and if the user has changed these while the application was in the background I need to have the screen refreshed. I have read that one should register for the UIApplicationWillEnterForegroundNotification using NSNotificationCenter.
How do you do this in MonoTouch? Or does anyone know an alternate way of ensuring that the screen is always kept up to date, even when returning from the background?
You could try something along the lines of:
//Register for the notification somewhere in the app
NSNotificationCenter.DefaultCenter.AddObserver(UIApplication.WillEnterForegroundNotification, EnteredForeground);
//snip
void EnteredForeground (NSNotification notification)
{
// do your stuff here
}
Bear in mind you would need to do this for every view controller you'd like to update when enterting from the background!
I have traced a problem in my iPhone app code to the viewDidAppear method not always firing. When you start the app the event fires as expected. However if I close the app using a phone capable of multitasking and reopen in. My viewDidAppear events no longer fire.
My views are loaded from Nibs and I use viewDidUnload to clean up (release and nil all outlets). My views are nested in side and tab bar then navigation controllers. I looks like the events aren't wired up properly when the nibs reload. Any idea on what I'm doing wrong/missing and how I can fix this?
Thanks in advance.
UPDATE I do not mean the event is not fired when the app first comes into the foreground. I mean the event never fires again. Even when changing between tabs or moving though the navigation views.
Example:
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
NSLog(#"viewDidAppear called");
}
This code is placed in two views, each on different tabs. Each time I swap between tabs "viewDidAppear called" is written to the log. When I close and reopen the app and swap between tabs this no longer happens. Other button events fire normally.
Btw, the viewDidUnload method is really badly named btw -- it's not an 'opposite' to viewDidLoad, it's only called if there was a low memory situation and the view for that controller was unloaded due to not being visible at that time.
(ORIGINAL, NOT SO RELEVANT ANSWER:)
Please see my answer to this similar question:
Why does viewWillAppear not get called when an app comes back from the background?
Basically, viewDidAppear gets called after your UIViewController's view was added to the application's UIWindow heirarchy. Backgrounding then restoring the app doesn't change your view in that respect, so viewDidAppear doesn't get called -- it's correct behaviour, and not a bug. Check out the API docs for UIViewController.
Found it.
While not new to programming I am new to iPhone development. On researching this problem I found it was not recommended to call the viewWillAppear and viewWillDisappear methods manually.
My viewWillDisappear methods resign any keyboards if shown, when my app enters the background it loads a splash screen ready for when the app re-enters the foreground (there is some logic I need to do to work out what the user is shown on restarting the app and I can do this under the splash screen).
As viewWillDisappear is not called when the app goes into the background to make sure no keyboards appeared over my splash screen I was calling viewWillDisapper in the applicationDidEnterBackground method. I guess this also un-registers my events.
By adding viewWillAppear to my applicationDidEnterForeground method my events started firing again. Lesson learned, I will refactor this so I don't call these events manually.
Thanks for the help.
I definitely need some clarification on when exactly viewDidAppear/viewDidDisappear methods are supposed to be called...
If the application enters background while showing some view, in this case I would expect viewDidDisappear to be called on the UIViewController linked to that view. On the other hand, if the application enters foreground after being background, I would expect viewDidAppear to be called. But it doesn't work this way.
If an UINavigationController displays an UIViewController we call 'A', and that UIViewController is linked to a view that has a subview linked to another UIViewController we call 'B', the viewDidAppear method is NOT called on the controller 'B'. Do I have to propagate viewDidAppear myself? I'm confused...
Thank you in advance!
They are not called because they don't disappear and reappear unless you tell them to disappear. Your whole application is suspended. You need to listen to the app delegates applicationDidBecomeActive: and applicationWillResignActive: messages if you want to know if your app got suspended or gets reactivated. You can also register for the notifications UIApplicationDidBecomeActiveNotification and UIApplicationWillResignActiveNotification.
Yes, you have to propagate the viewDidAppear: messages to your subviews manually. This is working as designed.
There is also:
(also an app delegate method):
- (void)applicationDidEnterBackground:(UIApplication *)application
When the user changes NsuserDefaults in settings on the iPhone and activates my app after it being suspended, i want to reload the active view.
How can i do this?
You could implement the applicationDidBecomeActive: method in your application delegate, or register for the UIApplicationDidBecomeActiveNotification notification in any other object.
- (void)applicationWillEnterForeground:(UIApplication*)application on the App Delegate is invoked when coming out of suspend.
Implement this method, in it check if the setting you are about has changed, find your topmost view controller and reload it's view then.