I want to perform some code when the segue goes back one step. For example, when the back button gets selected, I want to perform some code.
I can't create a new unwind action from the back button because there is no back button in the storyboard. Is there a way to insert code, as soon as the back button is selected?
If you want to stick with the default back button, one way to do this is to subclass the navigation controller, and override popViewControllerAnimated: which is called when you tap the back button.
-(UIViewController *)popViewControllerAnimated:(BOOL)animated {
UIViewController *vcToBePopped =[super popViewControllerAnimated:animated];
id vc = self.viewControllers.lastObject; // this will be the controller you're going back to
if ([vc isKindOfClass:IntendedViewController class]) { // replace IntendedViewController with the actual class name you care about
[(IntendedViewController *)vc someMethod];
}
return vcToBePopped;
}
Related
i have an app with three views:
FirstView
SecondView
ThirdView
When i am on the ThirdView and i click on the back button from navigation controller, i want to pass data from ThridView to SecondView.
But i don't know how to do this.
I don't want to add an extra button on my view.
The same when i'm on the SecondView and i want to go back to the FirstView.
I can't use the method "ViewWillDisappear" because if a set a "PerformSegueWithIdentifier" on this method to pass data from SecondView to FirstView, i can't switch to ThirdView because the "ViewWillDisappear" method will be executed.
Can you please help me?
PS: I use the language swift 2
In your viewWillDisappear or viewDidDisappear method you can check if back button is pressed by checking whether or not your view controller is moving from parent view controller.
override func viewWillDisappear(animated: Bool) {
if(self.isMovingFromParentViewController())
{
//Send data to previous view controller
print("Going back: Back button pressed");
}else{
print("Controller is hidden due to some other reason e.g Pushing another view controller");
}
}
I make subclass of UINavigationController because I cannot find Unwind Segue signature in UIViewController since Xcode 11.
#implementation CLUnwindNavigationController
- (BOOL)canPerformUnwindSegueAction:(SEL)action fromViewController:(UIViewController *)fromViewController withSender:(id)sender {
return NO;
}
- (IBAction)unwindForSegue:(UIStoryboardSegue *)unwindSegue towardsViewController:(UIViewController *)subsequentVC {
}
#end
You can find UnwindSegue signature.
You can connect to your desired action.
I have the following code in my custom method:
(IBAction)checkContinue:(UIButton *)sender {
if ([category.text isEqualToString:#""])
{
[self displayErrorMsg:#"Category Name cannot be empty"];
[category becomeFirstResponder];
}
//The else part doesn't work at all. When I click "Continue" the second view controller is shown and in that the error message in the "If" part is displayed.
else{
//This code will help to navigate from Menu types to Create Menu Screen
[self performSegueWithIdentifier:#"sw_contmenu" sender: self];
}
}
I have 2 segue for my MenuViewController: sw_contmenu and sw_newmenu, which will be executed from 2 different methods.
Problem: When I run the code and click Continue button, the above function is invoked with null values but the else part of the function doesn't work.
You have an extra action segue that is causing the second view controller to be pushed into view at the same you are handling the button press. These two operations are in conflict.
Deleting the action segue and adding a Show segue between the first view controller and second view controller should fix the problem.
I have the following storyboard in an application I am working on:
At the root, I have a Tab Bar Controller. It links to two View Controllers.
The first View Controller to display a newsfeed with pictures uploaded by the user (the one at the bottom in the storyboard).
The second View Controller serves to initiate the taking of a picture and attach some data to it. In the last step (top right), when touching "Save" in the right item of the Navigation bar, I want the user to be redirected to the newsfeed View Controller passing it some data.
I tried using a segue and it works. The data are passed to the newsfeed but the wrong tab is selected. I changed the selected tab using
[self.tabBarController setSelectedIndex:0];
But by tapping on the second tab again, things are messed up. I can see the newsfeed instead of the taking a picture screen. If I tap again, it crashes.
At some point I thought I may have got the wrong storyboard and should have implemented a TabBar in my newsfeed and handle the taking picture as a modal view.
Would you know any clean way to achieve this?
Thanks
You should not use a normal segue, which adds the destination controller to the stack. To do what you are trying to the best way should be to use an unwind segue. This is a rough sketch of what you need to do:
• Declare an unwind segue action in the NewsfeedController like (IBAction)unwindFromPictureSaved:(UIStoryboardSegue *)segue;
• Connect your "Save" button in your SavingPictureController to the "Exit" icon in the storyboard and select the previously defined method;
• In the newly created unwind segue define its identifier with something like SavedPictureSegue;
• Define the data to be passed in SavingPictureController's header with something like #property (strong, readonly, nonatomic) id passedData;
• In SavingPictureController implement
-(void)prepareForSegue:(UIStoryboardSegue *)segue
{
if ([segue.identifier isEqualToString:#"SavedPictureSegue"]) {
_passedData = // Your data here
}
}
• In NewsfeedController now implement the previously defined method and fetch the data from (SavingPictureController *)segue.sourceController. Be sure to #import "SavingPictureController.h".
Thanks to #Davide, I created a subclass of TabBarController and implemented the method below:
// Find the appropriate controller to answer to an unwind segue
// For each child view controller
// Checks if it is a Navigation Controller
// If it is check its children view controllers
// Return the first view controller that answers the unwind segue
// This because I assumed the default behavior is just to check one level up (in this case, it would have stopped at the NavigationController)
// Based on https://developer.apple.com/library/ios/technotes/tn2298/_index.html#//apple_ref/doc/uid/DTS40013591-CH1-CCVC-SELECTING_A_CHILD_VIEW_CONTROLLER_TO_HANDLE_AN_UNWIND_ACTION
- (UIViewController *)viewControllerForUnwindSegueAction:(SEL)action fromViewController:(UIViewController *)fromViewController withSender:(id)sender {
BOOL resChildren, res;
for(UIViewController *controller in self.childViewControllers) {
if ([controller isKindOfClass:[UINavigationController class]]) {
for (UIViewController *childController in controller.childViewControllers) {
resChildren = [childController canPerformUnwindSegueAction:action fromViewController:fromViewController withSender:sender];
if (resChildren) {
return childController;
}
}
}
res = [controller canPerformUnwindSegueAction:action fromViewController:fromViewController withSender:sender];
if (res) {
return controller;
}
}
return nil;
}
Then in the unwind method of the 'NewsFeedController" it is necessary to set the correct index to see the controller with something like:
[self.tabBarController setSelectedIndex:1];
I uploaded a demo on github at https://github.com/kintso/unwindSegueWithTabBarControllerAndNavigationController
Is there a way to tell if a new controller came from a navigation back button or was pushed onto the stack? Id like to reload data only for pushing on the navigation stack, not on a back button press.
As of iOS 5.0 you can do this:
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
if (self.isBeingPresented || self.isMovingToParentViewController) {
// "self" is being shown for the 1st time, not because of a "back" button.
}
}
If your push also includes instantiating the view controller, put your push-only logic in viewDidLoad. It will not be called on back because it has already been loaded.
You could implement the UINavigationControllerDelegate and override the `navigationController:didShowViewController:animated:' method. You'll then have to check the returned view controller to make a determination as to whether you came back from the expected view controller.
- (void)navigationController:(UINavigationController*)navigationController didShowViewController:(UIViewController*)viewController animated:(BOOL)animated
{
if (yourPushedViewController == viewController)
{
// Do something
}
}
I connected first view controller with the second one using StoryBoard Push Segue and Interface Builder.
The button is named GO on top/right.
I have three textfield that must be filled before going to second controller.
I display an alert when one of them is empty.
The problem is that my code after displaying correct alertView goes to SecondController instead of remaining on mainController.
if ([segue.identifier isEqualToString:#"DataDisplay"])
{
if (![self verifySelection]) {
return;
} else {
RowViewController *rowViewController = segue.destinationViewController;
// rowViewController.delegate = self;
}
}
1) You have a segue wired directly from your Go button to your Sensor Data view controller. You don't want this, because anytime someone touches Go, the segue is going to happen ... no stopping it. So, first step is to remove the segue you have going from Go to your second view controller.
2) Instead, wire the segue from the File's Owner icon below the view controller to the second view controller. Give it a name like DataDisplay.
3) In the IBAction for your Go button
if ([self verifySelection) {
[self performSegueWithIdentifier:#"DataDisplay" sender:self]
}
An easy fix would be to create the segue manually, rather than letting the interface builder manage it. So you would ctrl-drag from your main view controller to your second one, selecting push as the type of segue and assigning it an identifier through the identifier inspector, then you connect an IBAction to your Go button and in the method you perform the checks on the text fields before programmatically firing the segue with:
[self performSegueWithIdentifier:#"whateverIdentifierYouGaveYourSegue" sender:self];
Heads up: to create a manual segue from a viewcontroller to another one, you need to either zoom out in your storyboard or ctrl-drag from the yellow circle underneath the view!
Edit: Your IBAction connected to the button method should be something like the following:
- (IBAction)download:(id)sender {
if(text boxes are ok)
[self performSegueWithIdentifier:#"segueIdentifier" sender:self];
else
[self showWarning];
}
Make sure that you assigned the ID segueIdentifier to the segue you created in your storyboard.
Your problem is you are defining the "performSegueWithIdentifier" after displaying the alert.
I think the code you are doing is like this :
//AlertView Allocation
[alert show];
Perform Segue
If this is how you are doing, then you are doing it wrong.
You have to use the structure of If-Else Statements and put up the Perform Segue in the condition where all the textfields are filled.