I have two UIViewControllers, vc1 and vc2.
I want to switch between them. But before loading the view of the new view controller, I want to destroy/release/remove (I'm not sure abt the correct word to use here) the previous viewcontroller.
For example, when I am switching to vc2 from vc1 ,I want to destroy vc1 completely, so that when I return to vc1 from vc2, vc1 will be loaded from scratch (i.e. viewDidLoad will be executed).
Which type of view switching should I opt for?
presentModal...
addSubview.
I am not using a navigation controller.
Currently I am using the presentModal... method, but when I use dismissModalViewcontroller on the newly presented view controller, it doesn't show up a new instance of the previous view controller. Instead, it shows the already running instance of it.
I want the viewDidLoad method of the previous view controller to run when I dismiss the newly presented view controller.
What exactly needs to happen in viewDidLoad?
You also have viewWillAppear available to you, so it could be that you could move the required functionality there and still use the modal presentation.
See this answer. You can do this with or without animation.
Animate change of view controllers without using navigation controller stack, subviews or modal controllers?
Related
My UIViewController calls a function on my rootViewController which then called popToRootViewControllerAnimated to return the view to the rootController. This all works - great!
Unfortunately the UINavigationItem (toolbar at the top) seems to display a mashup of both the rootViewController and the UIViewController that has just been removed.
What do I need to do? What have I done wrong?
The navigation bar doesn't remember changes that were made to it, so when you push a new controller, the navigation bar is altered to give the title of the new view controller, but it doesn't store what was there for the previous view controller.
You will need to recreate the items in the toolbar each time you come back to the view controller that has custom items.
You might be able to do this on viewWillAppear instead of viewDidLoad. I can't recall exactly, but you should recreate custom controls on navigation toolbar because it does not get preserved when a new view controller is pushed.
It seems that calling popToRootViewController from the rootViewController messes things up. TO rectify this I called the following from within the calling UIViewController
[self.navigationController popViewControllerAnimated:YES];
By my count, the only two instances when viewWillAppear is called is when you initialize your view controller, or when you pop off the view controller that's on top of it on the navigation stack (ie pushing the back button on the viewcontroller ahead of it). Are there any other instances when viewWillAppar is called? I don't believe it's called when the app becomes active. Interested to hear some responses on this.
viewwillappear method is called as and when the view controller's view is added to the window. ( if the view is already in the window and is hidden by another view, this method is called when the view is once again revealed). The method is a notification to the view controller that the view is about to become visible. You can override this method to make any customizations with presenting the view.
This will also be called anytime addSubView is called, with your view.
Here's the scenario, switchViewController is the view added to the main window. So switchViewController is the main view, so if I want to go view B, I will addsubview of view B, there isn't a need to remove switchViewController's view right?
The issue is after I go back from view B to switchViewController's view, the method viewWillAppear is not being called anymore.
Why is it so?
viewWillAppear: is not called automatically when a view is removed from or added to the view hierarchy. It is the responsibility of the view controller to call it at the right time. The built-in view controller classes do this whenever you present or push a new view controller. Since you do not use this mechanism in your app, the method doesn't get called (unless you call it yourself).
That's because it never disappeared, you were just putting something else in front of it. If you want to navigate from one screen to another and back, they should be separate view controllers, and you should be using UINavigationController and its pushViewController:isAnimated: method.
It's not getting called beause your just modifying the first view, not navigating to a different one.
You might consider embedding your view in a Navigation controller, then calling your ViewB with
[navigationController pushViewController:viewB animated:YES];
I have an TabBar application with 4 tabs. All four tabs have navigation controllers. In the settings tab i have a table with a cell for "Feedback". When the cell is clicked a FeedBackView controller is pushed which contains a feedback form with a few fields. This has a textfield for Category. When the textfield is touched, a modal view controller (FeedBackModalView) is presented with a picker. In the viewDidLoad method of the FeedBackModalView controller I typed NSLog(#"%#", self.parentViewController). In the console it shows the parentViewController as TabBar controller. Why is that? Shouldn't it be showing the FeedBackView controller as the parentView since I'm presenting the modal view in that controller?
I hope i was clear.
Using presentModalViewController with UITabBarController has some issues, and I believe the internal behavior of the method has kept changing in recent SDK versions. The bottom line is, you are supposed to use the root view controller to modally present a view controller. In case you are using tab bar interface, that becomes the UITabBarController object.
In an old version of SDK, when I presented a modal view in a view controller inside a tab bar controller the modal view did not appear in full screen, which wasn't an expected or a documented behavior. Now a modal view seems to appear in full screen anywhere, and I wouldn't be surprised if [self presentModalViewController:animated:] method internally checks self and if it has non-nil parentViewController property, send the message to the parent view controller (which will explain your observation).
My memory is vague and perhaps somebody has to correct me. However, I still believe it's the straightforward thing to understand (and also maybe practice) presentModal... only works with the root view controller.
I'm starting an app where I'd like to have multiple view controllers. Some of the views will be displayed inside of a navigation controller. I can create a navigation controller and then add another instantiated view controller to it. But what I'd like to do, is just instantiate a view controller that has its own view and is the root view controller of a navigation view controller. So when I instantiate the view controller, I'd like for it create a navigation controller and push "self" on to it. When I do it my simulator crashes and the details don't really give a reason. The console does not display anything. Any ideas. My reason for this is to separate out logic without have a view controller that simply creates a navigation controller and then pushes another view controller on it as the root view controller.
I'm not entirely sure if I understand your question correctly. Why would it be preferable if the view controller pushed itself to the navigation controller? I mean, you have to instantiate your view controller at some point in code (either app delegate or another view controller) anyway. Why can't you just create the navigation controller there, instantiate your VC and then push it onto the nav controller? As far as I can see, this doesn't involve creating any additional view controllers.
Anyway, having a view controller decide by itself where it is used (ie. pushed onto), is not best practice. This way you lose the flexibility of using it in other contexts. Always try to couple your components as loosely as possible.