VoiceOver Z gesture won't trigger when UIAlertController is active - ios

I'm trying to use the Z gesture to dismiss a UIAlertController. I have a very simple app. It has a single view with 1 button. Tapping the button presents an alert. I have implemented
- (BOOL)accessibilityPerformEscape {
NSLog(#"Z gesture");
return YES;
}
With VoiceOver on, scrubbing the screen prints out "Z gesture," but when I press the button and the alert is visible, scrubbing the screen does nothing, the method is not called and nothing is printed. What do I have to do to get this to function while the alert is on screen?
Thanks...

To get the desired result on your alert view thanks to the scrub gesture, override accessibilityPerformEscape() in the alert view itself.
A solution could be to implement this override in an UIView extension as follows :
extension UIView {
override open func accessibilityPerformEscape() -> Bool {
if let myViewController = self.findMyViewController() as? UIAlertController {
myViewController.dismiss(animated: true,
completion: nil)
}
return true
}
private func findMyViewController() -> UIViewController? {
if let nextResponder = self.next as? UIViewController {
return nextResponder
} else if let nextResponder = self.next as? UIView {
return nextResponder.findMyViewController()
} else {
return nil
}
}
}
The code is short enough to be understood without further explanation. If it's not clear, don't hesitate to ask.
The function findMyViewController has been found here.

Related

Keyboard is appearing and immediately disappearing when UISearchBar.becomeFirstResponder() is getting called

I have UISearchController in the navigationItem.searchController and I want to make it focus when the user selects "Search" from the menu.
So shortly, when the user is tapping on the "Search" option in the menu (UITableViewCell) it's getting the view controller that have the searchController in it and calling:
guard let navigationVC = presentingViewController as? UINavigationController else { return }
guard let documentsVC = navigationVC.topViewController as? DocumentsViewController else { return }
documentsVC.searchController.searchBar.becomeFirstResponder()
Then, the UISearchBar is getting focus, the keyboard is appearing and then it's immediately disappearing, and I don't have any code that would make it disappear (like view.endEditing()).
1 GIF is worth more than 1,000 words:
So, after many tries I got some way to make it work, but I'm sure there is a much more elegant ways to do this, so if someone think that they have better way, please post it here and I may use it and mark your answer as the correct one.
Create the function focusOnSearchBar() in YourViewController:
func focusOnSearchBar() {
let searchBar = searchController.searchBar
if searchBar.canBecomeFirstResponder {
DispatchQueue.main.async {
searchBar.becomeFirstResponder()
}
} else {
DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) {
self.focusOnSearchBar()
}
}
}
What it actually do is use itself recursively and check (every 0.1 sec) if searchBar.canBecomeFirstResponder. This is the problematic/not elegant thing.
Then, add this to viewDidAppear():
if focusOnSearch {
searchController.isActive = true
}
Don't forget to add extension to your ViewController for UISearchControllerDelegate (and of course, set searchController.delegate = self) and implement didPresentSearchController (that will be invoke by setting searchController.isActive = true):
extension YourViewController: UISearchControllerDelegate {
func didPresentSearchController(_ searchController: UISearchController) {
if focusOnSearch {
focusOnSearchBar()
}
}
}
Now all you have to do is to set focusOnSearch = true in the prepare(for segue:sender:).
*Note: if you want to focusOnSearchBar while you are in the same viewController of the searchBar, just set:
focusOnSearch = true
searchController.isActive = true
And it will work by itself.
Make your searchbar first responder in the viewDidLoad method. That will make sure everything is ready before focusing the search bar.

Responder chain error

I want to translate this kind of Objective-C code to Swift:
- (UINavigationController *)targetNaviCtrl{
if(!_targetNaviCtrl){
UIResponder *target = self.nextResponder;
do {
target = target.nextResponder;
} while (![target isKindOfClass:UINavigationController.self] && target != nil);
_targetNaviCtrl = (UINavigationController *)target;
}
return _targetNaviCtrl;
}
// by iterate its next responder, so I can get access the target viewController to do something.
// This is often used across several hierarchies.
// A root B, B push C , C push D. I use A in D viewController.
I met some trouble.
code repo
Apple Doc: next
Declaration
var next: UIResponder? { get }
Return Value
The next object in the responder chain or nil if this is the last object in the chain.
I want to access the left tarBarController in the right viewController.
class ViewControllerEightLayer
// the right viewController.
class ViewControllerEightLayer: UIViewController {
override var next: UIResponder?{
get{
return super.next
}
}// the right viewController.
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
var nextResponder = self.next! // Here I call it
}
Here I call it, here is error info:
Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value
class LayerTableVC
// the center a little right UITableViewController.
class LayerTableVC: UITableViewController {
override var next: UIResponder?{
get{
return super.next
}
}// the center a little right UITableViewController.
class LayerNavigationVC
// the center a little left UINavigationController.
class LayerNavigationVC: UINavigationController {
override var next: UIResponder?{
get{
return super.next
}
}// the center a little left UINavigationController.
class MainTabBarVC
// the left tarBarController
class MainTabBarVC: UINavigationController {
override var next: UIResponder?{
get{
return self
}
}// the left tarBarController
I do not know how to solve it in this way. Any suggestions?
Maybe It helps,
self.next?.target(forAction: <#T##Selector#>, withSender: <#T##Any?#>)
It seems wired.
I did it by the code ,
let tabBarViewController = UIApplication.shared.keyWindow!.rootViewController as! UITabBarController
And I want to know the responder chain solution
PS:
aim of digging through the responder chain is curiosity.
It happened , I do not think it will happen .
So I wonder why.
I'd like to reverse-engineering.
PPS:
My intend is to control the tool bar to hide and show. Not providing data from to
extension ViewControllerEightLayer: UITextFieldDelegate{
func textFieldShouldReturn(_ textField: UITextField) -> Bool {
if textField.text == "1" {
tabBarViewController.tabBar.isHidden = false
}
else{
tabBarViewController.tabBar.isHidden = true
}
return true
}
This is a personal experiment project, not of my corp.
You seem to be asking for how to walk up the responder chain. Here's how.
func showResponderChain(_ r: UIResponder) {
var r : UIResponder! = r
repeat { print(r, "\n"); r = r.next } while r != nil
}

UIControl blocking all my views on iPhone

I got a iPad-designed app using a SplitViewController showing two views, one with a contacts list and another with details of this contact. The SplitView works well on iPad but has some problems on iPhones.
There is a UIControl that take all the size of the Master View, that check if there is any .touchDown interaction by the user and some methods called to enable or disable this UIControl depending if we are on editing contact mode or not allowing user to interact with the screen or not :
private var disableInteractionClosure: (()->())?
private lazy var interactionOverlay: UIControl = {
let c = UIControl()
c.autoresizingMask = [.FlexibleHeight, .FlexibleWidth]
c.addTarget(self, action: "interactionOverlayAction", forControlEvents: .TouchDown)
return c
}()
func disableInteractionWhileEditingWithClosure(callback: ()->()) {
if disableInteractionClosure == nil {
disableInteractionClosure = callback
/* display control overlay */
interactionOverlay.frame = navigationController!.view.bounds
navigationController!.view.addSubview(interactionOverlay)
}
}
func interactionOverlayAction() {
disableInteractionClosure!()
}
func enableInteraction() {
disableInteractionClosure = nil
interactionOverlay.removeFromSuperview()
}
Basically the UIControl is used to block user from switching between contact while user is editing another contact/ creating a new one by blocking interaction with the contact list and if changes have been made on the editing/creating view it fires a method that shows a pop up saying "modifications have been made do you want to continue without saving ? cancel or continue " :
func cancel() {
self.view.endEditing(true)
let closure: ()->() = {
self.layoutView.willResign()
self.delegate?.tabDetailsControllerDidCancel(self)
}
if layoutView.hasChanges() {
MKAlertViewController().instantaneousAlert(title: "Modification apportées", message: "Êtes-vous sur de vouloir continuer sans sauvegarder les modifications ?", confirmButtonTitle: "Oui", cancelButtonTitle: "Annuler", confirmed: { () -> Void in
closure()
}, canceled: { () -> Void in
})
} else {
closure()
}
}
It works fine on iPad because the UIControl is only above the Master View and is enabled when in editing mode on the Detail View (iPad 3D Debugging view), so the pop up shows only when manually cancelling the editing/creating or when trying to change contact while editing/creating, but as the splitView don't work the same on iPads and iPhones and it appears that on iPhone the Master View is placed above the Detail View, the UIControl is also above (iPhone 3D Debugging view), and it causes to block interactions on all the screen and wherever I click the cancel pop-up is shown.
Can you guys explain me a way to enable/show this UIControl only when the MasterView is showing and not everywhere. Thanks.
I ended up using the viewWillDisappear on the detail view :
override func viewWillDisappear(animated: Bool) {
super.viewWillDisappear(animated)
if self.isMovingFromParentViewController() || self.isBeingDismissed() {
if editingMode {
shared.contactsListController.disableInteractionWhileEditingWithClosure({ (_) in
self.tabDetailsController.cancel()
})
shared.contactsListController.disableToolbar()
} else {
shared.contactsListController.enableInteraction()
shared.contactsListController.enableToolbar()
}
self.navigationController?.toolbar.alpha = 1
}
}
and modifying the disableInteractionWhileEditingWithClosure method on the master view:
func disableInteractionWhileEditingWithClosure(callback: ()->()) {
if disableInteractionClosure == nil {
disableInteractionClosure = callback
/* display control overlay */
interactionOverlay.frame = navigationController!.view.bounds
view.addSubview(interactionOverlay) // this line
}
}
and it works ! :)

becomeFirstResponder returns true and keyboard is dismissed

In the following code I am trying to transfer control from UITextField to the next via a next button.
I am doing this by calling becomeFirstResponder on the next UITextField.
If I don't type anything in the first and current UITextField the next button works as expected. The keyboard stays up and the focus is transferred.
If I do type something, and only if the field is empty. The method becomeFirstResponder for the next field is called and returns true, yet the keyboard is dismissed and focus is not transferred.
public func numberPad(numberPad: APNumberPad, functionButtonAction:UIButton, textInput: UIResponder) {
var current:UITextField?
for field in editCells {
if (current != nil) {
field.valueTextField.becomeFirstResponder()
return;
}
if (field.valueTextField == activeField) {
current = field.valueTextField
}
}
textInput.resignFirstResponder()
}
This function is called when the NEXT or DONE button is pressed on the keyboard. Which is a custom number keypad. APNumberPad specifically.
https://github.com/podkovyrin/APNumberPad
It is my delegate function.
Anyone know any reason becomeFirstResponder would return true and not work, only in some cases, but work in others?
And yes this is the main UI thread. Adding a call to resignFirstResponder on the current field, then a delay and calling becomeFirstResponder works. This causes the keypad to flicker, no matter how small the delay though.
Edit... I am now doing this... and am living with the keyboard flicker for now:
Delay is a helper function for GCD
public func numberPad(numberPad: APNumberPad, functionButtonAction:UIButton, textInput: UIResponder) {
var current:UITextField?
for field in editCells {
if (current != nil) {
current?.resignFirstResponder()
delay (0) {
field.valueTextField.becomeFirstResponder()
}
return;
}
if (field.valueTextField == activeField) {
current = field.valueTextField
}
}
textInput.resignFirstResponder()
}
I don't know if it helps you, or not. I wrote a simple UITextField extension that contains a returnView variable which decides what the textfield should do on return key press:
turn to next text field (if the returnView is an UITextField)
simulate button touch (if the returnView is a UIButton)
or hide keyboard
class NextTextField: UITextField, UITextFieldDelegate {
#IBOutlet weak var returnView: UIView? {
didSet {
if returnView is UITextField {
returnKeyType = UIReturnKeyType.Next
}
}
}
override func awakeFromNib() {
super.awakeFromNib()
delegate = self
}
func textFieldShouldReturn(textField: UITextField) -> Bool {
if let nextTextField = self.returnView as? UITextField {
nextTextField.becomeFirstResponder()
} else if let nextButton = self.returnView as? UIButton {
nextButton.sendActionsForControlEvents(.TouchUpInside)
} else {
self.resignFirstResponder()
}
return true
}
}

Setting action for back button in navigation controller

I'm trying to overwrite the default action of the back button in a navigation controller. I've provided a target an action on the custom button. The odd thing is when assigning it though the backbutton attribute it doesn't pay attention to them and it just pops the current view and goes back to the root:
UIBarButtonItem *backButton = [[UIBarButtonItem alloc]
initWithTitle: #"Servers"
style:UIBarButtonItemStylePlain
target:self
action:#selector(home)];
self.navigationItem.backBarButtonItem = backButton;
As soon as I set it through the leftBarButtonItem on the navigationItem it calls my action, however then the button looks like a plain round one instead of the arrowed back one:
self.navigationItem.leftBarButtonItem = backButton;
How can I get it to call my custom action before going back to the root view? Is there a way to overwrite the default back action, or is there a method that is always called when leaving a view (viewDidUnload doesn't do that)?
Try putting this into the view controller where you want to detect the press:
-(void) viewWillDisappear:(BOOL)animated {
if ([self.navigationController.viewControllers indexOfObject:self]==NSNotFound) {
// back button was pressed. We know this is true because self is no longer
// in the navigation stack.
}
[super viewWillDisappear:animated];
}
I've implemented UIViewController-BackButtonHandler extension. It does not need to subclass anything, just put it into your project and override navigationShouldPopOnBackButton method in UIViewController class:
-(BOOL) navigationShouldPopOnBackButton {
if(needsShowConfirmation) {
// Show confirmation alert
// ...
return NO; // Ignore 'Back' button this time
}
return YES; // Process 'Back' button click and pop view controller
}
Download sample app.
Unlike Amagrammer said, it's possible. You have to subclass your navigationController. I explained everything here (including example code).
Swift Version:
(of https://stackoverflow.com/a/19132881/826435)
In your view controller you just conform to a protocol and perform whatever action you need:
extension MyViewController: NavigationControllerBackButtonDelegate {
func shouldPopOnBackButtonPress() -> Bool {
performSomeActionOnThePressOfABackButton()
return false
}
}
Then create a class, say NavigationController+BackButton, and just copy-paste the code below:
protocol NavigationControllerBackButtonDelegate {
func shouldPopOnBackButtonPress() -> Bool
}
extension UINavigationController {
public func navigationBar(_ navigationBar: UINavigationBar, shouldPop item: UINavigationItem) -> Bool {
// Prevents from a synchronization issue of popping too many navigation items
// and not enough view controllers or viceversa from unusual tapping
if viewControllers.count < navigationBar.items!.count {
return true
}
// Check if we have a view controller that wants to respond to being popped
var shouldPop = true
if let viewController = topViewController as? NavigationControllerBackButtonDelegate {
shouldPop = viewController.shouldPopOnBackButtonPress()
}
if (shouldPop) {
DispatchQueue.main.async {
self.popViewController(animated: true)
}
} else {
// Prevent the back button from staying in an disabled state
for view in navigationBar.subviews {
if view.alpha < 1.0 {
UIView.animate(withDuration: 0.25, animations: {
view.alpha = 1.0
})
}
}
}
return false
}
}
It isn't possible to do directly. There are a couple alternatives:
Create your own custom UIBarButtonItem that validates on tap and pops if the test passes
Validate the form field contents using a UITextField delegate method, such as -textFieldShouldReturn:, which is called after the Return or Done button is pressed on the keyboard
The downside of the first option is that the left-pointing-arrow style of the back button cannot be accessed from a custom bar button. So you have to use an image or go with a regular style button.
The second option is nice because you get the text field back in the delegate method, so you can target your validation logic to the specific text field sent to the delegate call-back method.
For some threading reasons, the solution mentionned by #HansPinckaers wasn't right for me, but I found a very easier way to catch a touch on the back button, and I wanna pin this down here in case this could avoid hours of deceptions for someone else.
The trick is really easy : just add a transparent UIButton as a subview to your UINavigationBar, and set your selectors for him as if it was the real button!
Here's an example using Monotouch and C#, but the translation to objective-c shouldn't be too hard to find.
public class Test : UIViewController {
public override void ViewDidLoad() {
UIButton b = new UIButton(new RectangleF(0, 0, 60, 44)); //width must be adapted to label contained in button
b.BackgroundColor = UIColor.Clear; //making the background invisible
b.Title = string.Empty; // and no need to write anything
b.TouchDown += delegate {
Console.WriteLine("caught!");
if (true) // check what you want here
NavigationController.PopViewControllerAnimated(true); // and then we pop if we want
};
NavigationController.NavigationBar.AddSubview(button); // insert the button to the nav bar
}
}
Fun fact : for testing purposes and to find good dimensions for my fake button, I set its background color to blue... And it shows behind the back button! Anyway, it still catches any touch targetting the original button.
Overriding navigationBar(_ navigationBar:shouldPop): This is not a good idea, even if it works. for me it generated random crashes on navigating back. I advise you to just override the back button by removing the default backButton from navigationItem and creating a custom back button like below:
override func viewDidLoad(){
super.viewDidLoad()
navigationItem.leftBarButton = .init(title: "Go Back", ... , action: #selector(myCutsomBackAction)
...
}
========================================
Building on previous responses with UIAlert in Swift5 in a Asynchronous way
protocol NavigationControllerBackButtonDelegate {
func shouldPopOnBackButtonPress(_ completion: #escaping (Bool) -> ())
}
extension UINavigationController: UINavigationBarDelegate {
public func navigationBar(_ navigationBar: UINavigationBar, shouldPop item: UINavigationItem) -> Bool {
if viewControllers.count < navigationBar.items!.count {
return true
}
// Check if we have a view controller that wants to respond to being popped
if let viewController = topViewController as? NavigationControllerBackButtonDelegate {
viewController.shouldPopOnBackButtonPress { shouldPop in
if (shouldPop) {
/// on confirm => pop
DispatchQueue.main.async {
self.popViewController(animated: true)
}
} else {
/// on cancel => do nothing
}
}
/// return false => so navigator will cancel the popBack
/// until user confirm or cancel
return false
}else{
DispatchQueue.main.async {
self.popViewController(animated: true)
}
}
return true
}
}
On your controller
extension MyController: NavigationControllerBackButtonDelegate {
func shouldPopOnBackButtonPress(_ completion: #escaping (Bool) -> ()) {
let msg = "message"
/// show UIAlert
alertAttention(msg: msg, actions: [
.init(title: "Continuer", style: .destructive, handler: { _ in
completion(true)
}),
.init(title: "Annuler", style: .cancel, handler: { _ in
completion(false)
})
])
}
}
This technique allows you to change the text of the "back" button without affecting the title of any of the view controllers or seeing the back button text change during the animation.
Add this to the init method in the calling view controller:
UIBarButtonItem *temporaryBarButtonItem = [[UIBarButtonItem alloc] init];
temporaryBarButtonItem.title = #"Back";
self.navigationItem.backBarButtonItem = temporaryBarButtonItem;
[temporaryBarButtonItem release];
Easiest way
You can use the UINavigationController's delegate methods. The method willShowViewController is called when the back button of your VC is pressed.do whatever you want when back btn pressed
- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated;
Here's my Swift solution. In your subclass of UIViewController, override the navigationShouldPopOnBackButton method.
extension UIViewController {
func navigationShouldPopOnBackButton() -> Bool {
return true
}
}
extension UINavigationController {
func navigationBar(navigationBar: UINavigationBar, shouldPopItem item: UINavigationItem) -> Bool {
if let vc = self.topViewController {
if vc.navigationShouldPopOnBackButton() {
self.popViewControllerAnimated(true)
} else {
for it in navigationBar.subviews {
let view = it as! UIView
if view.alpha < 1.0 {
[UIView .animateWithDuration(0.25, animations: { () -> Void in
view.alpha = 1.0
})]
}
}
return false
}
}
return true
}
}
Found a solution which retains the back button style as well.
Add the following method to your view controller.
-(void) overrideBack{
UIButton *transparentButton = [[UIButton alloc] init];
[transparentButton setFrame:CGRectMake(0,0, 50, 40)];
[transparentButton setBackgroundColor:[UIColor clearColor]];
[transparentButton addTarget:self action:#selector(backAction:) forControlEvents:UIControlEventTouchUpInside];
[self.navigationController.navigationBar addSubview:transparentButton];
}
Now provide a functionality as needed in the following method:
-(void)backAction:(UIBarButtonItem *)sender {
//Your functionality
}
All it does is to cover the back button with a transparent button ;)
I don't believe this is possible, easily. The only way I believe to get around this is to make your own back button arrow image to place up there. It was frustrating for me at first but I see why, for consistency's sake, it was left out.
You can get close (without the arrow) by creating a regular button and hiding the default back button:
self.navigationItem.leftBarButtonItem = [[[UIBarButtonItem alloc] initWithTitle:#"Servers" style:UIBarButtonItemStyleDone target:nil action:nil] autorelease];
self.navigationItem.hidesBackButton = YES;
There's an easier way by just subclassing the delegate method of the UINavigationBar and override the ShouldPopItemmethod.
This approach worked for me (but the "Back" button will not have the "<" sign):
- (void)viewDidLoad
{
[super viewDidLoad];
UIBarButtonItem* backNavButton = [[UIBarButtonItem alloc] initWithTitle:#"Back"
style:UIBarButtonItemStyleBordered
target:self
action:#selector(backButtonClicked)];
self.navigationItem.leftBarButtonItem = backNavButton;
}
-(void)backButtonClicked
{
// Do something...
AppDelegate* delegate = (AppDelegate*)[[UIApplication sharedApplication] delegate];
[delegate.navController popViewControllerAnimated:YES];
}
onegray's solution is not safe.According to the official documents by Apple,https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/CustomizingExistingClasses/CustomizingExistingClasses.html,
we should avoid doing that.
"If the name of a method declared in a category is the same as a method in the original class, or a method in another category on the same class (or even a superclass), the behavior is undefined as to which method implementation is used at runtime. This is less likely to be an issue if you’re using categories with your own classes, but can cause problems when using categories to add methods to standard Cocoa or Cocoa Touch classes."
Using Swift:
override func viewWillDisappear(animated: Bool) {
super.viewWillDisappear(animated)
if self.navigationController?.topViewController != self {
print("back button tapped")
}
}
Here is Swift 3 version of #oneway's answer for catching navigation bar back button event before it gets fired. As UINavigationBarDelegate cannot be used for UIViewController, you need to create a delegate that will be triggered when navigationBar shouldPop is called.
#objc public protocol BackButtonDelegate {
#objc optional func navigationShouldPopOnBackButton() -> Bool
}
extension UINavigationController: UINavigationBarDelegate {
public func navigationBar(_ navigationBar: UINavigationBar, shouldPop item: UINavigationItem) -> Bool {
if viewControllers.count < (navigationBar.items?.count)! {
return true
}
var shouldPop = true
let vc = self.topViewController
if vc.responds(to: #selector(vc.navigationShouldPopOnBackButton)) {
shouldPop = vc.navigationShouldPopOnBackButton()
}
if shouldPop {
DispatchQueue.main.async {
self.popViewController(animated: true)
}
} else {
for subView in navigationBar.subviews {
if(0 < subView.alpha && subView.alpha < 1) {
UIView.animate(withDuration: 0.25, animations: {
subView.alpha = 1
})
}
}
}
return false
}
}
And then, in your view controller add the delegate function:
class BaseVC: UIViewController, BackButtonDelegate {
func navigationShouldPopOnBackButton() -> Bool {
if ... {
return true
} else {
return false
}
}
}
I've realised that we often want to add an alert controller for users to decide whether they wanna go back. If so, you can always return false in navigationShouldPopOnBackButton() function and close your view controller by doing something like this:
func navigationShouldPopOnBackButton() -> Bool {
let alert = UIAlertController(title: "Warning",
message: "Do you want to quit?",
preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "Yes", style: .default, handler: { UIAlertAction in self.yes()}))
alert.addAction(UIAlertAction(title: "No", style: .cancel, handler: { UIAlertAction in self.no()}))
present(alert, animated: true, completion: nil)
return false
}
func yes() {
print("yes")
DispatchQueue.main.async {
_ = self.navigationController?.popViewController(animated: true)
}
}
func no() {
print("no")
}
Swift 4 iOS 11.3 Version:
This builds on the answer from kgaidis from https://stackoverflow.com/a/34343418/4316579
I am not sure when the extension stopped working, but at the time of this writing (Swift 4), it appears that the extension will no longer be executed unless you declare UINavigationBarDelegate conformity as described below.
Hope this helps people that are wondering why their extension no longer works.
extension UINavigationController: UINavigationBarDelegate {
public func navigationBar(_ navigationBar: UINavigationBar, shouldPop item: UINavigationItem) -> Bool {
}
}
By using the target and action variables that you are currently leaving 'nil', you should be able to wire your save-dialogs in so that they are called when the button is "selected". Watch out, this may get triggered at strange moments.
I agree mostly with Amagrammer, but I don't think it would be that hard to make the button with the arrow custom. I would just rename the back button, take a screen shot, photoshop the button size needed, and have that be the image on the top of your button.
You can try accessing the NavigationBars Right Button item and set its selector property...heres a reference UIBarButtonItem reference, another thing if this doenst work that will def work is, set the right button item of the nav bar to a custom UIBarButtonItem that you create and set its selector...hope this helps
For a form that requires user input like this, I would recommend invoking it as a "modal" instead of part of your navigation stack. That way they have to take care of business on the form, then you can validate it and dismiss it using a custom button. You can even design a nav bar that looks the same as the rest of your app but gives you more control.
To intercept the Back button, simply cover it with a transparent UIControl and intercept the touches.
#interface MyViewController : UIViewController
{
UIControl *backCover;
BOOL inhibitBackButtonBOOL;
}
#end
#implementation MyViewController
-(void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
// Cover the back button (cannot do this in viewWillAppear -- too soon)
if ( backCover == nil ) {
backCover = [[UIControl alloc] initWithFrame:CGRectMake( 0, 0, 80, 44)];
#if TARGET_IPHONE_SIMULATOR
// show the cover for testing
backCover.backgroundColor = [UIColor colorWithRed:1.0 green:0.0 blue:0.0 alpha:0.15];
#endif
[backCover addTarget:self action:#selector(backCoverAction) forControlEvents:UIControlEventTouchDown];
UINavigationBar *navBar = self.navigationController.navigationBar;
[navBar addSubview:backCover];
}
}
-(void)viewWillDisappear:(BOOL)animated
{
[super viewWillDisappear:animated];
[backCover removeFromSuperview];
backCover = nil;
}
- (void)backCoverAction
{
if ( inhibitBackButtonBOOL ) {
NSLog(#"Back button aborted");
// notify the user why...
} else {
[self.navigationController popViewControllerAnimated:YES]; // "Back"
}
}
#end
At least in Xcode 5, there is a simple and pretty good (not perfect) solution. In IB, drag a Bar Button Item off the Utilities pane and drop it on the left side of the Navigation Bar where the Back button would be. Set the label to "Back." You will have a functioning button that you can tie to your IBAction and close your viewController. I'm doing some work and then triggering an unwind segue and it works perfectly.
What isn't ideal is that this button does not get the < arrow and does not carry forward the previous VCs title, but I think this can be managed. For my purposes, I set the new Back button to be a "Done" button so it's purpose is clear.
You also end up with two Back buttons in the IB navigator, but it is easy enough to label it for clarity.
Swift
override func viewWillDisappear(animated: Bool) {
let viewControllers = self.navigationController?.viewControllers!
if indexOfArray(viewControllers!, searchObject: self) == nil {
// do something
}
super.viewWillDisappear(animated)
}
func indexOfArray(array:[AnyObject], searchObject: AnyObject)-> Int? {
for (index, value) in enumerate(array) {
if value as UIViewController == searchObject as UIViewController {
return index
}
}
return nil
}
Found new way to do it :
Objective-C
- (void)didMoveToParentViewController:(UIViewController *)parent{
if (parent == NULL) {
NSLog(#"Back Pressed");
}
}
Swift
override func didMoveToParentViewController(parent: UIViewController?) {
if parent == nil {
println("Back Pressed")
}
}
Swift version of #onegray's answer
protocol RequestsNavigationPopVerification {
var confirmationTitle: String { get }
var confirmationMessage: String { get }
}
extension RequestsNavigationPopVerification where Self: UIViewController {
var confirmationTitle: String {
return "Go back?"
}
var confirmationMessage: String {
return "Are you sure?"
}
}
final class NavigationController: UINavigationController {
func navigationBar(navigationBar: UINavigationBar, shouldPopItem item: UINavigationItem) -> Bool {
guard let requestsPopConfirm = topViewController as? RequestsNavigationPopVerification else {
popViewControllerAnimated(true)
return true
}
let alertController = UIAlertController(title: requestsPopConfirm.confirmationTitle, message: requestsPopConfirm.confirmationMessage, preferredStyle: .Alert)
alertController.addAction(UIAlertAction(title: "Cancel", style: .Cancel) { _ in
dispatch_async(dispatch_get_main_queue(), {
let dimmed = navigationBar.subviews.flatMap { $0.alpha < 1 ? $0 : nil }
UIView.animateWithDuration(0.25) {
dimmed.forEach { $0.alpha = 1 }
}
})
return
})
alertController.addAction(UIAlertAction(title: "Go back", style: .Default) { _ in
dispatch_async(dispatch_get_main_queue(), {
self.popViewControllerAnimated(true)
})
})
presentViewController(alertController, animated: true, completion: nil)
return false
}
}
Now in any controller, just conform to RequestsNavigationPopVerification and this behaviour is adopted by default.
Use isMovingFromParentViewController
override func viewWillDisappear(animated: Bool) {
super.viewWillDisappear(true)
if self.isMovingFromParentViewController {
// current viewController is removed from parent
// do some work
}
}
The answer from #William is correct however, if the user starts a swipe-to-go-back gesture the viewWillDisappear method is called and even self won't be in the navigation stack (that is, self.navigationController.viewControllers won't contain self), even if the swipe is not completed and the view controller is not actually popped. Thus, the solution would be to:
Disable the swipe-to-go-back gesture in viewDidAppear and only allow using the back button, by using:
if ([self.navigationController respondsToSelector:#selector(interactivePopGestureRecognizer)])
{
self.navigationController.interactivePopGestureRecognizer.enabled = NO;
}
Or simply use viewDidDisappear instead, as follows:
- (void)viewDidDisappear:(BOOL)animated
{
[super viewDidDisappear:animated];
if (![self.navigationController.viewControllers containsObject:self])
{
// back button was pressed or the the swipe-to-go-back gesture was
// completed. We know this is true because self is no longer
// in the navigation stack.
}
}
The solution I have found so far is not very nice, but it works for me. Taking this answer, I also check whether I'm popping programmatically or not:
- (void)viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
if ((self.isMovingFromParentViewController || self.isBeingDismissed)
&& !self.isPoppingProgrammatically) {
// Do your stuff here
}
}
You have to add that property to your controller and set it to YES before popping programmatically:
self.isPoppingProgrammatically = YES;
[self.navigationController popViewControllerAnimated:YES];

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