I have an odd problem with UIImagePickerControllerSourceTypeCamera. My application gives the choice to select a pic from the gallery, or take a photo with the camera. If I choose the gallery, I pick a photo and return to my view, no issues.
However, when using UIImagePickerControllerSourceTypeCamera, it appears to do something odd with my view when I return to it.
For example, I have a bunch of code in the viewDidLoad method which moves some objects in the view if it needs to based on some factors - this code gets called when I exit the UIImagePickerControllerSourceTypeCamera, but doesnt get called when I exit the gallery.
Is this expected?
I think your view is getting dumped by the didReceiveMemoryWarning thing which is being triggered by the resource-intensive camera stuff. You can force the simulator to generate a memory warning without the camera to test this theory.
Generally speaking, viewDidLoad needs to be able to deal with getting called multiple times. It's not an init method. It gets called again if self.view gets set to nil and the view later needs to be recreated. There may be a more appropriate place to put any code you have there that's causing problems, but the init methods are tricky because the designated initializer is bypassed by nib loading.
When loaded from a nib, the class's initWithCoder is called instead which bypasses the whole init process because dearchiving is assumed to be sucking in an already-initialized object. Therefore reinitializing the object might break stuff, like call loadView which essentially conflicts with what a nib contains as it's supposed to programmatically construct what the nib already has in it. You can still override initWithCoder as usual though as long as you pass through the args to super like you should, but then this will not get called if you initialize the object with the designated initializer. Of course if you need to worry about that you can put all the code you want executed in both into a method that gets called from both overridden methods.
Related
I am trying to load a list of assets using the ALAssetsLibrary and enumerateGroupsWithTypes. I populate an NSMutableArrary with the assets loaded so i get to use it later, for instance change a view's background randomly.
I tried to preload this array with the assets in the ViewDidLoad method and only to find out that it gets handled AFTER the view is loaded. if I put a NSLog statement after the load method is called, the log will be printed, but no array initialized until the view is completely loaded.
Question is when should I initialize my array then?
thanks!
The viewDidLoad method does exactly as it suggests - its called once the view is loaded. No surprises there. You could consider loading in the initWithFrame: and/or initWithCoder: methods, depending on which is relevant to you.
Your question doesn't say much about why you want to load something in this method. What's wrong with loading it in, say, the viewDidLoad method and using the array to configure the view before the view will appear? I have no idea how heavy your loading is. But guess what - there's even a handy viewWillAppear: method...!
This is driving me crazy.
I am under the impression that awakeFromNib Method is called only once(even when that view is visited again), correct me if i am wrong.
I have an app with 3 views.
The last one being the subclass of a UIview where i draw using drawRect.
I had a working code with the method awakeFromNib in the last view, with the method being called only once how many ever times i visit the view.
Now i deploy the app to my device and update my Xcode to version 4.
When i run the code again and debug, the method awakeFromNib is called everytime the view is visited.
I dont think update would do such a crazy thing, but i am thoroughly confused.
Is there some kind of a memory leak or am i missing something?
Thank you
I am under the impression that awakeFromNib Method is called only once(even when that view is visited again), correct me if i am wrong.
-awakeFromNib will be called on each instance of a class whenever an instance of that class is loaded from a nib file. You should be able to expect it to only be called once on a particular instance but should handle it being called many times on different instances of any given class.
UIViewControllers will unload their views when they receive a memory warning and their view is not visible. The view will be reloaded the next time the view controller's 'view' property is called. You should understand and support this behavior to minimize your app's memory use as it allows you to only keep the currently visible views in memory at any given time.
It sounds like you are not expecting that controller's view to be unloaded and reloaded from your nib.
I am working on the iTuneU Stanford iPhone course HelloPoly drawing assignment, and I am getting a call to my object's init routine when I don't expect one. The callback seem to indicate that the call is coming from _loadMainNibFile (after other calls). What I am trying to understand is why is my object being init-ed implicitly. The source files can be found here: -- http://www.cavedrawings.com/hp2_files.zip
Can anyone tell me why the init routine would be called implicitly when loading the NIB file?
Most implementations of initWithCoder: ultimately call another initialization function. It's normal to stack initialization methods when you have a series of them that progressively add information to the initialization process.
_loadMainNibFile calls the initWithCoder: of the file owner of the nib which in turn calls another initialization method which leads up to the final init.
When a nib is loaded all objects within it get instantiated to do any prep work they need to do.
If you want a nib's object loaded and init'd later, put the object in a separate nib and explicitly load that nib when you need it.
I've implemented a View Controller, and I'm trying to do some very basic initialization in initWithNibFile...which I understand to be the designated initializer for View Controller objects.
I've tried to put breakpoints on the code, and have put very simple NSLog statements into it as well. Regardless...I'm not seeing it be executed (and the object i'm attempting to alloc/init inside the function is also not being allocated - so I'm about 99% sure I'm not hitting the code.
Is there something I need to do elsewhere to cause this method to be invoked?
I'm getting a clean build, no warnings or errors. And the app successfully loads up the View, and I can invoke a ButtonClick method I've coded and connected to this same View Controller.
Any suggestions would be appreciated.
TC
I ended up moving my allocation logic to viewDidLoad, and that works fine.
Not sure why the initWithNibFile was not working...but I'll take the small victory !!!
Thanks for offering to look at the code bpapa.
You probably need initWithCoder: It's what the SDK uses to read from nib files during startup.
initWithNibFile: is almost never called by the system. Usually you call this manually. The documentation is quite misleading on this point.
In any case, be careful doing too much initialization in the initWithXXXX methods. The view's targets and actions aren't likely to be set up and connected yet. viewDidLoad is almost always the right place to do viewController setup anyways.
I found out this:
applicationDidFinishLaunching (an delegate method of the UIApplicationDelegate Protocol) seems to be called BEFORE my views from the nib file are loaded completely. So I tried all the day to change an image of an UIImageView right after my app launched in the iPhone simulator, but nothing happened.
Then I wrote a little action method that I call with the press of a button. And then it happened: WORKS!
So the applicationDidFinishLaunching delegate method isn't really the right place for stuff that has to be done after the app is really "ready". I gues there's something better that waits for the nib to be loaded completely. but where? and what?
I gues there's something better that waits for the nib to be loaded completely. but where? and what?
For application specific things like global settings, preferences, etc., -appDidFinishLaunching is the right place.
For UIView specific things, you typically use the -viewDidLoad method in a UIVIewController subclass. It is pretty much the only place you are guaranteed that the nib file is loaded, the IBOutlets are initialized and the IBActions are attached.
This is difference from the Mac OS X world, where -awakeFromNib was the place to do it.
Hey until your views and their view controllers instantiated you can't modify their ui. However just for the sake of your problem you can always declare the uiimageview as a property of your app delegate class and initialize it in the appDidFinishLaunching event. But that's the worst practise. As on the iPhone which has limited memory always lazy load ie: only initialize objects when and just before they are actually required by your UI. So ideally you should be doing this in the viewDidLoad event of the view where you want to use this UIImageView.
applicationDidFinishLaunching is usually used for stuff like database file checks, opening database connection, populating global variables, any other application wide logic, checking for an available Internet connection etc