What function gets triggered when a user hits the back button on a push page? I need to set some properties before going back to the previous page. ViewWillDisapper is not what I'm looking for
You will want to use either viewWillDisappear or viewDidDisappear to monitor a user going back on a pushed page (assuming you mean this is inside a navigation controller).
Just like when you call your instance method of UINavigationController to "pushViewController:(BOOL)animated:" guess what method is called to POP a view controller? try something like
[self.navigationBar.backButton //Not sure if this is what its called addTarget:self selector:#selector(popViewController)]
and fill in the rest of the method with UIEventTouchUpInside so when the user presses the back button on navigation bar it will jump into you're overrided function.
Make your View inherit UINavigationController protocols and then overide popViewController method.
I suggest looking at UINavigationController class reference if that didn't answer your question.
Related
I need a way to change text depending of user input, when user tap back button. I followed that solution: Find out if user pressed the back button in uinavigationcontroller?
and did add following code in viewDidLoad:
if ([self isMovingFromParentViewController]) {
NSLog(#"isMoved");
[self.delegate stringChangedTo:self.myTextField.text atIndex:self.indexToPass];
}
However, nothing changed. More to say, method is not called (NSLog dont output a string).
How could i find a way to call delegate when user tap back button?
That code needs to be in viewWillDisappear: or viewDidDisappear:. not viewDidLoad.
viewDidLoad is called when the view controller's view is loaded. You want to call the delegate when the view controller is being dismissed.
There is also a UINavigationControllerDelegate protocol. You can get notified when a given view controller is shown by implementing either of these:
-navigationController:willShowViewController:animated:
-navigationController:didShowViewController:animated:
ADDENDUM:
In my opinion, using the delegate is a cleaner design, because you get notified precisely when a navigation event occurs. View controller life cycle methods such as -viewDidDisappear:, etc. can get called when you present/dismiss a modal view controller, and require that you add logic to discern those.
I'm sure this will be a simple answer, maybe a method I'm missing to implement. Here goes:
In my Controller1 I use a pushViewController to push a new view Controller2 onto my view stack. I'm getting a back button.
Now, when Back button is pressed in my Controller1 I want to be able to detect that Controller2 is being popped and we're back in Controller1. Makes sense?
I was trying to do that with ViewDidAppear, but I'm not sure how to detect a popped controller. There are other answers here but they all show examples in Controller2 on viewWillDisappear
How would I do that in Swift?
Without knowing more you should pass a reference of the first controller to the second controller so that the second controller can tell the first when it is done (this is a simple delegate relationship, it could also be implemented using a block / closure).
Ideally the first controller should be responsible for dismissing the second controller, either when it gets this callback or, more appropriately, directly when the 'dismiss' button is tapped.
I have two navigation Controllers for my views. I need to perform some operations when the user presses the back button to go to the previous view. Normally I would do this using the prepareForSague() function and using the sague Identifier.
What's the identifier (or how do I get it) of the back button that comes with navigation controller so i can use it in my prepareForSague function. Or is it done in other ways?
Please follow the steps:
I think you have to first create custom button
Assign it as back button of Navigation controller.
Add target selector to that button and usepopToViewController: method.
Or
Do connection with back button
Add action to it
write your back button logic in that method.
Just place your code inside viewWillDissapear
override func viewWillDisappear(animated: Bool)
That is, don't try to change the behavior of the back button, just write whatever code you need to be executed inside viewWillDissapear
you have to use "viewWillDissapear" method for this, if you wanna use default back button.
But you may have to be careful here coz you only need this to work when really going back by back button, so every other actin - which calls "viewWillDissapear" method, you may need to make a flag to know its not the back action.
One way of doing this would be to use the ViewWillDisappear() function to detect when the navigation back button is pressed. Found the answer here.
your class can implement the UINavigationControllerDelegate protocol and implement this method:
- (void)navigationController:(UINavigationController*)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated
I'm having trouble piecing this all together. I have a view controller that opens up another (pushes it on to the navigation stack). On that presented view controller, the user enters a value in a text view. When the user pushes the back button in the navigation, I want to be able to pass the value that they entered in the text view back to the presenting controller.
I've looked for a way to use unwind segue with the back button but haven't found anything. When I create my back button (programmatically) I use initWithTitle:style:target:action but I'm not sure how in implementing the action method that I'll be able to access the value set in the presented controller. Might have to use a delegate to link the two, but not sure of the exact integration point for this scenario.
I feel like I'm so close here and a little help would get me there. Thanks!
The two most common models to use for this interaction are for the child view controller to have either a delegate or a completion block. Either would be set in the prepareForSegue method. My personal preference is the completion block method just because it keeps code contained, but ymmv.
There are also multiple models for detecting when your child view controller is dismissed and you need to invoke the delegate and/or completion:
Use a custom back button. Not a fan of this as it can be an issue to create a back button that really looks and acts like the Apple original, especially if supporting iOS 6 and iOS 7.
Hook viewDidDisappear and see if you're still in the navigation controller's viewControllers array. This is better as the back button works right, but it still feels kind of hokey.
Use the UINavigationBarDelegate method navigationBar:shouldPopItem: This is attractive, especially if you have other validation that needs to happen like checking for saved/unsaved values. To implement this you'll have to subclass UINavigationController and forward the method to your child view controller.
EDIT: Details on Option 2:
-(void)viewDidDisappear:(BOOL)animated
{
[super viewDidDisappear:animated];
if(![self.navigationController.viewControllers containsObject:self])
{
// We're not still in the navigation stack so we must've been
// popped. If we were pushed, viewDidDisappear would be called
// but viewControllers containsObject:self would be true
}
}
EDIT: Clarified Option 3: in your navigation controller subclass
- (BOOL)navigationBar:(UINavigationBar *)navigationBar shouldPopItem:(UINavigationItem *)item
{
UIViewController* top = self.topViewController;
if([top respondsToSelector:#selector(navigationBar:shouldPopItem:)])
return [(id)top navigationBar:navigationBar shouldPopItem:item];
return [super navigationBar:navigationBar shouldPopItem:item];
}
Then you can implement navigationBar:shouldPopItem: in the classes that need the functionality.
the back button does not actually comes up with any event associated with itself so that you can pass the values between the previous and to be Popped ViewController.
You would have to implement Delegate pattern to pass values. In this case as you cant catch when backButton is pressed, you need to use custom leftBarButtonItem or use a image with < in itself.
I am trying to segue back to a home screen and pop everything from the stack (of views?)
I am using UINavigationController:
[self.navigationController popToRootViewControllerAnimated:YES];
Where shall I call this method? I have tried in -(void) prepareForSegue which does not work.
Basically I want to make sure when I go back to home screen there is no back button on the left of the title.
Home screen here refers to the welcome screen of my App.
I am not sure which part of my code shall be posted. Please comment if you need to see my code.
Thank you in advance.
Assuming you're using a Storyboard, and a UIButton declared over there is the one that triggers that action you wanna perform, you should declare an IBAction: -(IBAction)buttonPressed:(id)sender; in the .h and implement it in the .m. Inside that method should appear that [self.navigationController popToRootViewControllerAnimated:YES]; code. Also remember to attach that action to that UIButton when touch up inside in the storyboard.
Hope it helped!
I think your confusion is around the concepts of what a segue is and how it relates to the navigation controller stack. The stack is exactly the same as the basic data structure stack (http://en.m.wikipedia.org/wiki/Stack_(abstract_data_type)) in that it's a last-in-first-out store. When you segue, you're normally adding to that stack, e.g. Pushing a new VC onto the stack. A back button in most cases would not be doing that. It would be popping, or removing from the stack. Which is why you probably wouldn't call pop methods from the prepareForSegue method. Instead try calling it at some other point, like when they tap the back button, or after some action has taken place.