I have a UIViewController that pops up a custom UIView that needs to be able to present another UIViewController (BarcodeScanViewController).
When the user is done with the BarcodeScanViewController, data is passed back to the UIView to update a label.
How can I present the BarcodeScanViewController from the UIView with the a navigation bar so I close it if necessary?
The below code kinda works. It present the BarcodeScanViewController, but it doesn't actually do anything. Its just a black view.
Inside Custom UIView
- (void) startScan {
BarcodeScanViewController * bsvc = [[BarcodeScanViewController alloc] init];
bsvc.delegate = self;
UIViewController *currentTopVC = [self currentTopViewController];
[currentTopVC presentViewController:bsvc animated:YES completion:nil];
}
I also receive an warning
Assigning to
'id < BarcodeScanViewControllerDelegate > ' from incompatible type 'CustomView * const__strong'
when I try to assign the delegate.
I have never called UIViewController from a UIView before. I know that only a VC can call another VC. So I tried to create VC to use a presenter.
What am I doing wrong?
Okay, there were a bunch of smaller things. I forked your repo and fixed it so that you can see how it works. See here.
In short: You did present the scanner VC, but as I said you can't simply put it "over" the presenting view controller (your ViewController class). As soon as any presentation transitions (i.e. animations) are done, the view of that ViewController is removed from the view hierarchy. So what you saw as a black screen was just the window background (which is black). The scanner's view was transparent. Furthermore, the scanner expected you to provide a view to render the camera into (and buttons) via an IBOutlet. Since you didn't instantiate the controller from a storyboard, you didn't set any, i.e. the view used for that was nil and thus the frame the scanner wanted to render the video in had a size of (0, 0).
I fixed that for now, hopefully you can now see how presenting a viewcontroller is supposed to work. To achieve an actual popup (with "underlying views of previous view controllers") is a bit harder on iOS, but possible in several ways. I can elaborate further later if you want.
I'm working on few views in an app that doesn't fit to any of standard Apple ViewControllers and I'm looking for a best solution for my problem.
Here is a quick mockup how it looks like:
http://pl.tinypic.com/r/2va1kbc/5
I have a main ViewController which is build of out 2 parts:
1. Top part which is always visible containing some logo
2. Content part which is changing - every content is a class (extending UIViewController)
Now tricky part is I want to do some animations in between of content changes - when user clicks a button on first one, top part slides down - pushing current viewController down, covers full screen and than slides up with a new viewController content.
So question is how to build it so it's easy to use and extend later (like UINavigationController).
I created a main view as UIViewController and added topView using:
LogoUIViewController *logoViewController = [[LogoUIViewController alloc] init];
[self.view addSubview:logoViewController.view];
LoginViewController *loginViewController = [[LoginViewController alloc] init];
loginViewController.delegate = self;
[self.view addSubview:loginViewController.view];
I'm using delegate to initialize a transition on main view controller, because I couldn't find a better way of doing it.
But with that solution I stucked because of those problems:
1. How to make content view controller to only use part of screen (change it size) ?
2. How to animate those 2 views so it will look like top layer is pushing away content ?
3. How to exchange views in an easy way (like UINavigationController popViewController way) and initialize animation automatically between them.
I know those are 3 problems, but I think it can be solved with better way of constructing the main view controller. Does anyone have experience with custom navigation systems like that ?
A UIPageViewController could be helpful. It would contain your content view controllers. The root vc that contains the page view controller can also be made it's delegate.
When you want to initiate a content view change, the root vc can do any animation it likes with it's page vc's view (like slide it down to reveal a larger header view). When the page transition is complete, as the delegate, the root vc can get notified with
- (void)pageViewController:(UIPageViewController *)pageViewController didFinishAnimating:(BOOL)finished previousViewControllers:(NSArray *)previousViewControllers transitionCompleted:(BOOL)completed
and then animate the restoration of it's view. Pretty simple, I think, and saves you a fair amount of effort on the container vc pattern. Xcode's default Paged App template is a really good starting point.
I am working with the project of ios and doing well in it. But now i stuck at one place where i am having three views (Say 1stview, 2ndview, 3rdview). I am navigating to second view from first view and third view using the code line below.
[self.navigationController pushViewController:first view animated:YES];
How can i check on second view wheather i am navigating from first view or third view. So that i can use particular condition on it.
So please help me out regarding this issue. Your help will be much appreciable.
Take a variable in second View controller. When you are creating the object of it, set proper value into it. Later on when it will get pushed, you can use that value to take proper decisions.
In the file of FirstViewController you will write below lines:
SecondController *controller = [[SecondController alloc]init];
controller.flag = 1; //That means you came here from viecontroller 1
[self.navigationController pushViewController:controller animated:YES];
In the file of ThirdViewcontroller you will write below lines:
SecondController *controller = [[SecondController alloc]init];
controller.flag = 3; //That means you came here from viecontroller 3
[self.navigationController pushViewController:controller animated:YES];
Try to arrange thing so that the 2ndView doesn't know about 1stView or 3rdView, but instead just changes it's behavior according to how it was configured. So, let's say that when you're navigating to 2ndView from 1stView, 2nd should display with a green background and when you get there from 3rd it should use blue instead. Rather than telling 2nd which controller preceded it, have the preceding controller just tell 2nd what background color to use. Same goes for any other aspect of 2ndView's behavior.
The benefit of doing it this way is that you can change 1st or 3rd without having to change anything in 2nd, and you can later add a 4thView or 5thView that also use 2ndView without having to change 2ndView.
Implement the method – navigationController:willShowViewController:animated: from the UINavigationControllerDelegate Protocol Reference. Inside this method you can check the navigation stack to get the current view controller using several properties of UINavigationController. An example would be access the visibleViewController property.
As #Apurv pointed out you need some sort of identifier mechanism to be able to know which view controller the call came from. e.g.: viewController.view.tag
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.
I create a ViewController named "YLJTestViewController" by interface builder ,code is like:
-(IBAction)DoneButtonPressed:(id)sender
{
YLJTestViewController *testViewController = [[YLJTestViewController alloc]initWithNibName:#"YLJTestViewController" bundle:nil];
[self.navigationController pushViewController:testViewController animated:YES];
//[self.view addSubview:testViewController.view];
}
but when I use [self.view addSubview:textViewController.view];it crashed,but use [self.navigationController pushViewController:testViewController animated:YES];it works well,so what's the difference?I thought they are the same...
pushViewController is like adding a piece of paper onto a stack of paper, while addSubView is like gluing a piece of paper onto another paper.
There is no explicit relationships between the previous view and the new view of the view controller which is pushed (like the pieces of paper are still separated in the stack). While the parent view will keep a strong reference to its subviews (like glue).
-addSubview: is a method of UIView. It inserts a view into another view. Like adding a button on a page.
-pushViewController: is a method of UINavigationController. It pushes a view controller onto a navigation stack. Like sliding from a table view to a details view.
In short, -addSubview: composes a view. -pushViewController: is a transition between views.
As sptrakesh states in this Apple Support forum thread:
addSubview is a lower level feature, which you use to add additional
views to your parent/main view. pushViewController replaces the
current main view in your window with the view associated with the new
view controller. You use presentModalViewController when you want to
display a view modally (blocks previous view) on top of your current
view. If you use full screen for your modal view controller, there is
not too much difference between pushViewController and this in terms
how the UI behaves. When you use pushViewController you can "pop" to
any view controller in the array of view controllers that have been
pushed, which is not as easy to do with nested modal views.
In your case the problem is not the use of addSubview: vs. pushViewController:animated:, but simply a typo when you use addSubview:.
[self.view addSubview:textViewController.view]; // misspelled
Should be (replacing x with s)
[self.view addSubview:testViewController.view]; // correct
As for the difference between addSubview: vs. pushViewController:animated:, others have already made good answers. Basically you should use pushViewController:animated: when you replace your entires screen's content, and addSubview: when you add non-full screen UI elements to an existing view.
When we are talking about the view of a UIViewController, pushViewController:animated: should be your preferred method.
I've recently ran into similar problems with addSubview and pushViewController. Everyone here has made great comments, but I would add one things:
Usually addSubview is not used by itself. You usually are using it with presentModalViewController, or in the case of controller containment, addChildViewController.
So in summary:
If you are using navigation controllers, you use pushViewController/popViewController to navigate through your app.
If you are manually switching views, use presentModalViewController.
If you are doing controller containment, use addChildViewController.
If you are using story boards, use Segues.