I want to make sure that all my initializations for my views and stuff are handled every time my application starts, even when it is called back after being sent to the background, such as with multitasking.
What's the best way to do this? should i use applicationDidBecomeActive to call viewDidLoad on my viewcontroller directly? I'm guessing this is not wise. I just want to make sure that stuff gets done on load every time the user calls up the app, no matter what state it is in at the time.
I have several apps published that do just that - call viewDidLoad on one or several UIViewControllers from applicationDidBecomeActive.
It works just fine. Apple doesn't object to it either.
However, be aware that if you have allocations in your viewDidLoad you need to either check for already allocated instances or release the instances you allocate in viewDidLoad when your app suspends. The same goes for DB connections that need to be closed, notification listeners, and so on.
As long as you watch for these elements and handle them correctly, the approach is valid and very usable.
Related
Do I need to cancel the opened connections (NSURLConnection) when I leave the view?
I'd do that in viewWillDisappear or viewDidDisappear but I don't know whether I actually need to do that.
If you're using ARC, there's a good chance your NSURLConnection objects (assuming they are instance variables or that you're holding onto them in memory somehow) will get magically released when the view controller goes away.
But to be sure, and to be nice, you should cancel the open connections. Doing the NSURLConnection object "cancel" in either "viewWillDisappear" or "viewDidDisappear" should work well.
Lets say I have multiple View controller classes using the same UIAlertView *alertView. *alertView's delegate is set to a centralized delegate.
I do this because would like to use the .tag to do different things based on it.
The question is every time I invoke an alert view or dismiss it, what do i have to do to prevent a memory leak?
Should I not release every time? Or is this a very bad idea?
Thanks.
A UIAlertView may be "shown" from anywhere in your app. I have an app that the main UIViewController has a timer that every so often brings up a UIAlertView. When that timer goes off, even if my main view being shown is from a completely different UIViewController (and thus view) the Alert will come to front.
If you really want to "actively" bring up the UIAlertView from any of your UIViewControllers (lets say based upon a user action), then I would do one of two things.
1) setup my Application Delegate Object with the UIAlertView implemented there, with accessor methods for invoking (showing) the Alert view, and thus freeing it from there also, or
2) Generate a singleton like object with the AlertView implemented there!!!
In either case then you can simply dealloc your UIAlertView once within the dealloc routine you write for either of those placements, and alloc it only once when the object is initialized.
Just treat it like you would any other object. If you want to keep it around, assign it to a retained property like: self.myAlert. You still need to release it like you normally would when creating it. The retained property will take care of keeping it around for you.
Always keep your retains(alloc's, copy's, etc...) and releases balanced.
I am wondering does the CLLocationManager delegates like didEnterRegion and didExitRegion work when stopUpdatingLocation is called or the the method startUpdatingLocation must called all the time to make them called ?
Another thing is where the best place to start regions monitoring
If your app enters the background you are expected to call stopUpdatingLocation to preserve energy. If you use startMonitoringForRegion:desiredAccuracy: your delegate methods didEnterRegion and didExitRegion will be called accordingly, even if your app is in background/suspended. Another option is to use startMonitoringSignificantLocationChanges. Then your app will be woken up from suspended or terminated status.
In my app, every time a user switches to a new view a sound will be played. Also, every time a button is tapped, a sound will be played.
The sounds to be played are the same for each case, so for example, sound.caf will be used many times and will be the same for every view.
My problem is that I cant think of a clever place to alloc these sounds, thats visible to all views. Is this possible? I dont want to alloc the sound everytime a view is created because I think it's a waste of time.
Is there someplace where I can alloc these sounds, and play them from any view in my program? Thanks!
The simplest solution would probably be to use the app delegate for that purpose because it's a singleton class (there is only one instance of it per application) and it can be accessed by any class easily: [UIApplication sharedApplication].delegate
You could set up the sound(s) in the applicationDidFinishLaunching: method so they're ready to go when your app is.
I'm working on a simple proof-of-concept for an iPhone app (and important bit of info, I'm pretty new to Mac OSX development all around). I created a view based app with a timer. I declared my NSTimer in the interface of my app's controller, used #property and #synthesize, and I initialize it in the controller's viewDidLoad method with scheduledTimerWithTimeInterval method. My selector is a method with the signature -(void)someMethod:(NSTimer *)timer which is declared in the interface and defined in the implementation file of the controller as well. I can step past the line where I assign the timer and see that it points to a valid object, but my program goes no further than the end of the viewDidLoad method and never reaches the breakpoint at the first line of my method that is called by the timer. Also, I see GDB: Program received bad signal: "EXC_BAD_ACCESS" in the status bar of xcode at this point (viewDidLoad end is reached). I didn't do anything in IB but add a view and a picker just so I'd see if the UI actually loads...it never does.
So, am I doing something wrong with the NSTimer, or are my troubles elsewhere? How can I use the debugging tools in xcode to get more information?
EXC_BAD_ACCESS usually indicates a memory management error, without seeing the code probably from somewhere else in your app. It's a very common error for beginners, but an important subject to fully understand, so I'd suggest looking through some of the questions on memory management here and find a few guides or tutorials to look through. It's actually pretty easy to learn.
Also, it shouldn't hurt but unless you need to access the timer in between fire events, you don't actually need to store it as an instance variable. Once you create and start a timer it's added to and retained by the application's run loop.
Have you got NSZombieEnabled?
Might be useful if this is failing on an over released object.