Hey,
I'm adding a UIViewcontroller as a subview of my current view. With something like that:
[self.view addSubview:viewcontroller.view];
The user can interact with that added viewcontroller so I can't just release it after I added it's view as my subview, right ?
So I would like to release it the dealloc methode and set it to nil in viewDidUnload when my master viewcontroller gets unloaded, right ?
The problem is, the viewcontoller I add as a subview is not added every time. So the question is, how can I ceck if the viewcontroller was added as subview and if so, release it.
Thx a lot !
Sebastian
You can check it like this:
if(viewController)
{
[viewController release];
viewController=nil;
}
and yes u need to put this in your dealloc method.
If you read correctly your code:
[self.view addSubview:viewcontroller.view];
it is not the controller which is being added as a subview, rather the view it manages.
This is an important point, since it means that the controller itself does not get retained. What is retained is the view.
So you can simply go on releasing your viewController in -dealloc as usual:
-(void)dealloc {
[viewController release]; viewController = nil;
...
}
and in your viewController's dealloc you will need to release the managed view, if you allocated it manually (or wherever it makes sense for your controller to release its view, if necessary).
On the other hand, whenever your superview is deallocated, then also the view you added as a subview will be released (as per Apple spec of addSubview behavior). So nothing to worry about here. Just release the viewController properly (and make that the view controller manages correctly tis own view).
One more note: you should not release your view controller in viewDidUnload.
In some open source code that I used to contribute to, we had a macro called RELEASE_TO_NIL which did exactly this.
#define RELEASE_TO_NIL(obj) if(obj != nil) { [obj release]; obj = nil; }
You would use it like this:
RELEASE_TO_NIL(viewController);
Simple as that.
Just add an tag to viewController.view and test if self.view contains that tag.
UIView *testView = [self.view viewWithTag:yourTag];
if(testView!=nil){
doStuff;
}
According to the Apple docs, a UIViewController instance should manage a view that fills the whole screen. If your view does not fill the screen, you could either subclass UIView to handle delegation or make the superview work as a delegate.
Also, the subviews of a view are contained in an instance of NSArray, do [myView subviews] to return this property. Ask the returned array if it contains the subview in question and you can release accordingly.
But, without knowing more, it does sound like you need to rethink how you're setting all this up.
My application is loading a first view (used to login into a Web service). When the login is successful, it performs a CATransition (basic kCATransitionFromRight) to show a second view and hides the first view. I've set the delegate of the transition to self so I can use -(void)animationDidStop:(CATransition *)theAnimation finished:(BOOL)flag.
When that method is called (right after the transition is over) I want to release the first view since I won't need it anymore. However, when I call [firstView release] (in animationDidStop:) the retain count doesn't seem to change. I used [loginView retainCount] to check this and since I know it's not always reliable I was wondering: am I doing this right?
Thank you.
taken from the book "Cocoa Touch for iPhone OS 3" is a similar approach.
They set up an animation remove the old subview, add the new one and then commit the animation.
Jilouc in his comment is right, forget to check "retaincount"...
if you want to be sure that your object view firstView just add a
NSLog(#"i'm removing myFirstView");
in its
-(void)dealloc{
}
method...
if you get that NSLog in debugger console window then be sure you had it removed/released in the right way...
btw... the right way could be something like this:
in animationDidStop:
if (firstView!=nil){
[firstView.view removeFromSuperview];
[firstView release];
firstView=nil;
}
I'm very new to xCode and objective-C so I wanted to make a simple textRPG.
I'm currently making a character creation process consisting of 4 xib-files. The only way I got switching views to work was to look at the utility-template. Problem is, now I have the first screen being the delegate for the second screen, being the delegate for the third screen etc. So by the end of the character creation process I can't dismiss the views because that just "steps back" through the views.
When I've searched around for a solution I've found a addSubview-method but it seems like that makes a new view, like, empty to arrange programmatically.
All I need is a simple way to switch from one loaded xib to another xib. Have I misunderstood addSubview or do I need something completely different?
(If it helps: I've worked with VB for several years, in case you notice that I missed some kind of concept concerning views and such)
Thanks in advance! :)
Use this code. It is really simple and works well.
View *view = [[View alloc] initWithNibName:#"xibNameGoesHere" bundle:nil];
view.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
[self presentViewController:view animated:YES completion:nil];
This will switch to another xib file and the two views won't own one another. I am using it in my own game right now.
#Joakim Ok, this is the way I do it. I have a class called RootViewController : UIViewContoller, whose view I add directly to the window. Then I make a subclass of UIView i.e. MyView. All of my views then subclass MyView. I also make an enum for all my views. In RootViewController you should have a switchView:(int)view method that looks something like this:
-(void) switchView:(myView) view
{
[_currentView removeFromSuperview];
switch(view)
{
case titleView:
_currentView = [[TitleView alloc] initWithRoot:self];
break;
case homeView:
_currentView = [[HomeView alloc] initWithRoot:self];
break;
default: break;
}
[self.view addSubview:_currentView];
[_currentView release];
}
in #interface RootViewContoller define MyView *_currentView;
TitleView and HomeView both subclass MyView and have a common method -(id)initWithRoot:(RootViewController*) rvc.
To switch between views use [_rvc switchView:homeView];
Hope this helps :)
It is called UINavigationController. Idea is
1) You push corresponding 'next' controller into navigation controller each time user submits current screen. Bonus - you'll get 'back' button for free on each step of character creation.
2) After character is created you pop all character creation controllers from stack.
Please read View Controller Programming Guide for iOS before trying to 'switch views' and such. You'll save tons of time and nerves.
another idea is not to use interface builder at all. i have been working with iphone apps for two years now and found that interface builder really prolongs the time to actually make something. make your own root controller and think about the logic you need to navigate through the views.
So in my app delegate I add a call add the myViewController.view to the main window:
1. [window addSubview:myViewController.view];
In myViewController I do the following code in the viewDidAppear method:
2. [self presentModalViewController: yourViewController animated: YES];
In my yourViewController class I do the following to try and go back to the main window
3. [self dismissModalViewControllerAnimated:YES];
My main windows view appears with buttons in all, but the buttons won't react to any click or anything. It's like there is something over them that I can't see.
Also, the main windows button works before this process but doesn't after the process.
Any help would be appreciated.
If the dismiss method call is in the modal view controller (not the parent that presents it), then you actually want to call [self.parentController dismissModalViewControllerAnimated:YES];
There are a number of reasons why things might not be responding to your touches. Here are two that have happened to me:
The frame of the view you want to touch is too small. UIViews can draw outside of their frames, so it might look ok, but not respond if the touch is technically outside of the frame -- you also have to check that all the superview's up the hierarchy also have a large enough frame.
If anything in your view is a UIImageView or child thereof, it won't respond to user touches because UIImageView has userInteractionEnabled set to NO by default. You can fix this just by setting myImageView.userInteractionEnabled = YES;
Edit: Oli pointed out in the comments that dismissModalViewControllerAnimated: should work if called on either self.parentController or simply self, since that method is smart enough to call the parent if needed, according to the docs. The docs also make it sound like this might behave differently if you have multiple model views open at once, though, so I would still consider it cleaner code to call the method on self.parentController directly.
I've read numerous posts about people having problems with viewWillAppear when you do not create your view hierarchy just right. My problem is I can't figure out what that means.
If I create a RootViewController and call addSubView on that controller, I would expect the added view(s) to be wired up for viewWillAppear events.
Does anyone have an example of a complex programmatic view hierarchy that successfully receives viewWillAppear events at every level?
Apple's Docs state:
Warning: If the view belonging to a view controller is added to a view hierarchy directly, the view controller will not receive this message. If you insert or add a view to the view hierarchy, and it has a view controller, you should send the associated view controller this message directly. Failing to send the view controller this message will prevent any associated animation from being displayed.
The problem is that they don't describe how to do this. What does "directly" mean? How do you "indirectly" add a view?
I am fairly new to Cocoa and iPhone so it would be nice if there were useful examples from Apple besides the basic Hello World crap.
If you use a navigation controller and set its delegate, then the view{Will,Did}{Appear,Disappear} methods are not invoked.
You need to use the navigation controller delegate methods instead:
navigationController:willShowViewController:animated:
navigationController:didShowViewController:animated:
I've run into this same problem. Just send a viewWillAppear message to your view controller before you add it as a subview. (There is one BOOL parameter which tells the view controller if it's being animated to appear or not.)
[myViewController viewWillAppear:NO];
Look at RootViewController.m in the Metronome example.
(I actually found Apple's example projects great. There's a LOT more than HelloWorld ;)
I finally found a solution for this THAT WORKS!
UINavigationControllerDelegate
I think the gist of it is to set your nav control's delegate to the viewcontroller it is in, and implement UINavigationControllerDelegate and it's two methods. Brilliant! I'm so excited i finally found a solution!
Thanks iOS 13.
ViewWillDisappear, ViewDidDisappear, ViewWillAppear and
ViewDidAppear won't get called on a presenting view controller on
iOS 13 which uses a new modal presentation that doesn't cover the
whole screen.
Credits are going to Arek Holko. He really saved my day.
I just had the same issue. In my application I have 2 navigation controllers and pushing the same view controller in each of them worked in one case and not in the other. I mean that when pushing the exact same view controller in the first UINavigationController, viewWillAppear was called but not when pushed in the second navigation controller.
Then I came across this post UINavigationController should call viewWillAppear/viewWillDisappear methods
And realized that my second navigation controller did redefine viewWillAppear. Screening the code showed that I was not calling
[super viewWillAppear:animated];
I added it and it worked !
The documentation says:
If you override this method, you must call super at some point in your implementation.
I've been using a navigation controller. When I want to either descend to another level of data or show my custom view I use the following:
[self.navigationController pushViewController:<view> animated:<BOOL>];
When I do this, I do get the viewWillAppear function to fire. I suppose this qualifies as "indirect" because I'm not calling the actual addSubView method myself. I don't know if this is 100% applicable to your application since I can't tell if you're using a navigation controller, but maybe it will provide a clue.
Firstly, the tab bar should be at the root level, ie, added to the window, as stated in the Apple documentation. This is key for correct behavior.
Secondly, you can use UITabBarDelegate / UINavigationBarDelegate to forward the notifications on manually, but I found that to get the whole hierarchy of view calls to work correctly, all I had to do was manually call
[tabBarController viewWillAppear:NO];
[tabBarController viewDidAppear:NO];
and
[navBarController viewWillAppear:NO];
[navBarController viewDidAppear:NO];
.. just ONCE before setting up the view controllers on the respective controller (right after allocation). From then on, it correctly called these methods on its child view controllers.
My hierarchy is like this:
window
UITabBarController (subclass of)
UIViewController (subclass of) // <-- manually calls [navController viewWill/DidAppear
UINavigationController (subclass of)
UIViewController (subclass of) // <-- still receives viewWill/Did..etc all the way down from a tab switch at the top of the chain without needing to use ANY delegate methods
Just calling the mentioned methods on the tab/nav controller the first time ensured that ALL the events were forwarded correctly. It stopped me needing to call them manually from the UINavigationBarDelegate / UITabBarControllerDelegate methods.
Sidenote:
Curiously, when it didn't work, the private method
- (void)transitionFromViewController:(UIViewController*)aFromViewController toViewController:(UIViewController*)aToViewController
.. which you can see from the callstack on a working implementation, usually calls the viewWill/Did.. methods but didn't until I performed the above (even though it was called).
I think it is VERY important that the UITabBarController is at window level though and the documents seem to back this up.
Hope that was clear(ish), happy to answer further questions.
As no answer is accepted and people (like I did) land here I give my variation. Though I am not sure that was the original problem. When the navigation controller is added as a subview to a another view you must call the viewWillAppear/Dissappear etc. methods yourself like this:
- (void) viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
[subNavCntlr viewWillAppear:animated];
}
- (void) viewWillDisappear:(BOOL)animated
{
[super viewWillDisappear:animated];
[subNavCntlr viewWillDisappear:animated];
}
Just to make the example complete. This code appears in my ViewController where I created and added the the navigation controller into a view that I placed on the view.
- (void)viewDidLoad {
// This is the root View Controller
rootTable *rootTableController = [[rootTable alloc]
initWithStyle:UITableViewStyleGrouped];
subNavCntlr = [[UINavigationController alloc]
initWithRootViewController:rootTableController];
[rootTableController release];
subNavCntlr.view.frame = subNavContainer.bounds;
[subNavContainer addSubview:subNavCntlr.view];
[super viewDidLoad];
}
the .h looks like this
#interface navTestViewController : UIViewController <UINavigationControllerDelegate> {
IBOutlet UIView *subNavContainer;
UINavigationController *subNavCntlr;
}
#end
In the nib file I have the view and below this view I have a label a image and the container (another view) where i put the controller in. Here is how it looks. I had to scramble some things as this was work for a client.
Views are added "directly" by calling [view addSubview:subview].
Views are added "indirectly" by methods such as tab bars or nav bars that swap subviews.
Any time you call [view addSubview:subviewController.view], you should then call [subviewController viewWillAppear:NO] (or YES as your case may be).
I had this problem when I implemented my own custom root-view management system for a subscreen in a game. Manually adding the call to viewWillAppear cured my problem.
Correct way to do this is using UIViewController containment api.
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
UIViewController *viewController = ...;
[self addChildViewController:viewController];
[self.view addSubview:viewController.view];
[viewController didMoveToParentViewController:self];
}
I use this code for push and pop view controllers:
push:
[self.navigationController pushViewController:detaiViewController animated:YES];
[detailNewsViewController viewWillAppear:YES];
pop:
[[self.navigationController popViewControllerAnimated:YES] viewWillAppear:YES];
.. and it works fine for me.
A very common mistake is as follows.
You have one view, UIView* a, and another one, UIView* b.
You add b to a as a subview.
If you try to call viewWillAppear in b, it will never be fired, because it is a subview of a
iOS 13 bit my app in the butt here. If you've noticed behavior change as of iOS 13 just set the following before you push it:
yourVC.modalPresentationStyle = UIModalPresentationFullScreen;
You may also need to set it in your .storyboard in the Attributes inspector (set Presentation to Full Screen).
This will make your app behave as it did in prior versions of iOS.
I'm not 100% sure on this, but I think that adding a view to the view hierarchy directly means calling -addSubview: on the view controller's view (e.g., [viewController.view addSubview:anotherViewController.view]) instead of pushing a new view controller onto the navigation controller's stack.
I think that adding a subview doesn't necessarily mean that the view will appear, so there is not an automatic call to the class's method that it will
I think what they mean "directly" is by hooking things up just the same way as the xcode "Navigation Application" template does, which sets the UINavigationController as the sole subview of the application's UIWindow.
Using that template is the only way I've been able to get the Will/Did/Appear/Disappear methods called on the object ViewControllers upon push/pops of those controllers in the UINavigationController. None of the other solutions in the answers here worked for me, including implementing them in the RootController and passing them through to the (child) NavigationController. Those functions (will/did/appear/disappear) were only called in my RootController upon showing/hiding the top-level VCs, my "login" and navigationVCs, not the sub-VCs in the navigation controller, so I had no opportunity to "pass them through" to the Nav VC.
I ended up using the UINavigationController's delegate functionality to look for the particular transitions that required follow-up functionality in my app, and that works, but it requires a bit more work in order to get both the disappear and appear functionality "simulated".
Also it's a matter of principle to get it to work after banging my head against this problem for hours today. Any working code snippets using a custom RootController and a child navigation VC would be much appreciated.
In case this helps anyone. I had a similar problem where my ViewWillAppear is not firing on a UITableViewController. After a lot of playing around, I realized that the problem was that the UINavigationController that is controlling my UITableView is not on the root view. Once I fix that, it is now working like a champ.
I just had this problem myself and it took me 3 full hours (2 of which googling) to fix it.
What turned out to help was to simply delete the app from the device/simulator, clean and then run again.
Hope that helps
[self.navigationController setDelegate:self];
Set the delegate to the root view controller.
In my case problem was with custom transition animation.
When set modalPresentationStyle = .custom viewWillAppear not called
in custom transition animation class need call methods:
beginAppearanceTransition and endAppearanceTransition
For Swift. First create the protocol to call what you wanted to call in viewWillAppear
protocol MyViewWillAppearProtocol{func myViewWillAppear()}
Second, create the class
class ForceUpdateOnViewAppear: NSObject, UINavigationControllerDelegate {
func navigationController(_ navigationController: UINavigationController, willShow viewController: UIViewController, animated: Bool){
if let updatedCntllr: MyViewWillAppearProtocol = viewController as? MyViewWillAppearProtocol{
updatedCntllr.myViewWillAppear()
}
}
}
Third, make the instance of ForceUpdateOnViewAppear to be the member of the appropriate class that have the access to the Navigation Controller and exists as long as Navigation controller exists. It may be for example the root view controller of the navigation controller or the class that creates or present it. Then assign the instance of ForceUpdateOnViewAppear to the Navigation Controller delegate property as early as possible.
In my case that was just a weird bug on the ios 12.1 emulator. Disappeared after launching on real device.
I have created a class that solves this problem.
Just set it as a delegate of your navigation controller, and implement simple one or two methods in your view controller - that will get called when the view is about to be shown or has been shown via NavigationController
Here's the GIST showing the code
ViewWillAppear is an override method of UIViewController class so adding a subView will not call viewWillAppear, but when you present, push , pop, show , setFront Or popToRootViewController from a viewController then viewWillAppear for presented viewController will get called.
My issue was that viewWillAppear was not called when unwinding from a segue. The answer was to put a call to viewWillAppear(true) in the unwind segue in the View Controller that you segueing back to
#IBAction func unwind(for unwindSegue: UIStoryboardSegue, ViewController subsequentVC: Any) {
viewWillAppear(true)
}
I'm not sure this is the same problem that I solved.
In some occasions, method doesn't executed with normal way such as "[self methodOne]".
Try
- (void)viewWillAppear:(BOOL)animated
{
[self performSelector:#selector(methodOne)
withObject:nil afterDelay:0];
}
You should only have 1 UIViewController active at any time. Any subviews you want to manipulate should be exactly that - subVIEWS - i.e. UIView.
I use a simlple technique for managing my view hierarchy and have yet to run into a problem since I started doing things this way. There are 2 key points:
a single UIViewController should be used to manage "a screen's worth"
of your app
use UINavigationController for changing views
What do I mean by "a screen's worth"? It's a bit vague on purpose, but generally it's a feature or section of your app. If you've got a few screens with the same background image but different overlays/popups etc., that should be 1 view controller and several child views. You should never find yourself working with 2 view controllers. Note you can still instantiate a UIView in one view controller and add it as a subview of another view controller if you want certain areas of the screen to be shown in multiple view controllers.
As for UINavigationController - this is your best friend! Turn off the navigation bar and specify NO for animated, and you have an excellent way of switching screens on demand. You can push and pop view controllers if they're in a hierarchy, or you can prepare an array of view controllers (including an array containing a single VC) and set it to be the view stack using setViewControllers. This gives you total freedom to change VC's, while gaining all the advantages of working within Apple's expected model and getting all events etc. fired properly.
Here's what I do every time when I start an app:
start from a window-based app
add a UINavigationController as the window's rootViewController
add whatever I want my first UIViewController to be as the rootViewController of the nav
controller
(note starting from window-based is just a personal preference - I like to construct things myself so I know exactly how they are built. It should work fine with view-based template)
All events fire correctly and basically life is good. You can then spend all your time writing the important bits of your app and not messing about trying to manually hack view hierarchies into shape.