I'm trying to remove the background view for my UITargetPreview. I made the background color clear, however, you can still see the frame of the background.
This is what it currently looks like:
I currently have a view that has the text container and the image inside of it and that's what I use as the view for the UITargetedPreview.
Is there a way to only show the image and the text and not the background frame?
There is a tricky method to hide the shadow and to do that you should find a view with _UIPlatterSoftShadowView class name in the view hierarchy and then hide it.
func viewByClassName(view: UIView, className: String) -> UIView? {
let name = NSStringFromClass(type(of: view))
if name == className {
return view
}
else {
for subview in view.subviews {
if let view = viewByClassName(view: subview, className: className) {
return view
}
}
}
return nil
}
override func tableView(_ tableView: UITableView, willDisplayContextMenu configuration: UIContextMenuConfiguration, animator: UIContextMenuInteractionAnimating?) {
DispatchQueue.main.async {
if let window = UIApplication.shared.delegate?.window! {
if let view = self.viewByClassName(view: window, className: "_UIPlatterSoftShadowView") {
view.isHidden = true
}
}
}
}
NOTE: It's not documented internal class and can be changed anytime further but it works now on both ios 13/14.
Have you tried subclassing the UIView as a UIControl?
I had a similar issue but in my case the view for UITargetedPreview was glitchy. However, changing the UIView to a UIControl fixed everything.
try removing shadow of that background view.
You need to study UIBezierPath() to outline the specific area you want to enclose before you present the target view.
After that, you shall assign the specific path to shadow path / visible path
let params = UIPreviewParameters()
params.backgroundColor = .clear
if #available(iOS 14.0, *) {
params.shadowPath = bubblePath
} else {
params.visiblePath = bubblePath
}
I have to move the UIView in only last UITextField in Swift 3.0 on mentioned below delegate method using tag,
func textFieldDidBeginEditing(_ textField: UITextField) {
if (textField.tag == 4){
//UIView Up
}
}
func textFieldShouldEndEditing(_ textField: UITextField) -> Bool {
if (textField.tag == 4){
//UIView Down
}
return true
}
I tried many codes but none of them are working like notification,..etc.
You need to add Observers into the NotificationCenter for listening to both when Keyboard goes up and down (i'll assume your textfield outlet is lastTextField for this example to work but this obviously have to be adapted to whatever name you've had provide for it)
IBOutlet weak var passwordTextField: UITextField!
NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow(_:)), name: .UIKeyboardWillShow, object: nil)
NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide(_:)), name: .UIKeyboardWillHide, object: nil)
(Code above can be added in viewDidLoad())
Then you add methods to be executed when those notifications arrive, like this:
func keyboardWillShow(_ notification:Notification) {
if view.frame.origin.y >= 0 && lastTextField.isFirstResponder {
view.frame.origin.y -= getKeyboardHeight(notification)
}
}
func keyboardWillHide(_ notification:Notification) {
if view.frame.origin.y < 0 {
view.frame.origin.y += getKeyboardHeight(notification)
}
}
Validations within those methods prevent double execution like moving up/down twice when moving between textfields without resigning first responder which is common in cases like your (i assume your doing this for a form hence the clarification you only need it for the fourth textfield). Notice i'm only doing validation in for the specified textfield (with its outlet lastTextField) in the keyboardWillShow method, this in case you move thor another textfield while the keyboard is shown and resign responder from it in which case, even though it isn't the original place where you started, the view will return to its original place when the keyboard is hidden.
You'll also need a method for getting keyboard's height, this one can help with that:
func getKeyboardHeight(_ notification:Notification) -> CGFloat {
let userInfo = notification.userInfo
let keyboardSize = userInfo![UIKeyboardFrameEndUserInfoKey] as! NSValue // of CGRect
return keyboardSize.cgRectValue.height
}
Let me know how it goes but i just tested this same code on my app and it works so you should be fine.
PS: pay close attention to the storyboard (if you're using it) and that delegate for textfields are set up properly.
The problem you are trying to remedy is rather complicated, because it requires you to:
Find the textField which is firstResponder
Calculate where that TextField is relative to it's superViews
Determine the distance for the animation, so that the containing
superview doesnt jump out of the window, or jumps too
much/repeatedly
Animate the proper superView.
As you can see.. it's quite the algorithm. But luckily, I can help. However, this only works for a hierarchy which has the following layout:
superView (view in the case of UIViewController) > (N)containerSubviews > textFields
where N is an integer
or the following:
superView (view in the case of UIViewController) > textFields
The idea is to animate superView, based on which textField is firstResponser, and to calculate if it's position inside of the SCREEN implies that it either partially/totally obstructed by the Keyboard or that it is not positioned the way you want for editing. The advantage to this, over simply moving up the superView when the keyboard is shown in an arbitrary manner, is that your textField might not be positioned properly (ie; obstructed by the statusbar), and in the case where your textfields are in a ScrollView/TableView or CollectionView, you can simply scroll the texfield into the place you want instead. This allows you to compute that desired location.
First you need a method which will parse through a given superView, and look for which of it's subViews isFirstResponder:
func findActiveTextField(subviews : [UIView], textField : inout UITextField?) {
for view in subviews {
if let tf = view as? UITextField {
guard !tf.isFirstResponder else {
textField = tf; break
return
}
} else if !subviews.isEmpty {
findActiveTextField(subviews: view.subviews, textField: &textField)
}
}
}
Second, to aleviate the notification method, also make a method to manage the actual animation:
func moveFromDisplace(view: UIView, keyboardheight: CGFloat, comp: #escaping (()->())) {
//You check to see if the view passed is a textField.
if let texty = view as? UITextField {
//Ideally, you set some variables to animate with.
//Next step, you determine which textField you're using.
if texty == YourTextFieldA {
UIView.animate(withDuration: 0.5, animations: {
self./*the proper superView*/.center.y = //The value needed
})
comp()
return
}
if texty == YourTextFieldB {
// Now, since you know which textField is FirstResponder, you can calculate for each textField, if they will be cropped out by the keyboard or not, and to animate the main view up accordingly, or not if the textField is visible at the time the keyboard is called.
UIView.animate(withDuration: 0.5, animations: {
self./*the proper superView*/.center.y = //The Value needed
})
comp()
return
}
}
}
Finally, the method which is tied to the notification for the keyboardWillShow key; in this case, i have a UIViewController, with an optional view called profileFlow containing a bunch of UITextFields
func searchDisplace(notification: NSNotification) {
guard let userInfo:NSDictionary = notification.userInfo as NSDictionary else { return }
guard let keyboardFrame:NSValue = userInfo.value(forKey: UIKeyboardFrameEndUserInfoKey) as? NSValue else { return }
let keyboardRectangle = keyboardFrame.cgRectValue
let keyboardHeight = keyboardRectangle.height
let keybheight = keyboardHeight
var texty : UITextField? //Here is the potential textfield
var search : UISearchBar? //In my case, i also look out for searchBars.. So ignore this.
guard let logProfile = profileFlow else { return }
findActiveTextField(subviews: [logProfile], textField: &texty)
//Check if the parsing method found anything...
guard let text = texty else {
//Found something.. so determine if it should be animated..
moveFromDisplace(view: searchy, keybheight: keybheight, comp: {
value in
search = nil
})
return
}
//Didn't find anything..
}
Finally, you tie in this whole logic to the notification:
NotificationCenter.default.addObserver(self, selector: #selector(searchDisplace(notification:)), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
I can't provide more content to the code, since it all depends on your view hierarchy, and how you want things to animate. So it's up to you to figure that out.
On a side note, usually, if you have so many textfields that to lay them out properly means they overstep the length of the screen.. it's probable that you could simplify your layout. A way to make this algorithm better would be to make sure you have all your textfields in one containing view, which again can become heavy for when, say, you use AutoLayout constraints. Odds are if you're in this situation, you can probably afford to add a flow of several views etc.
There is also the fact that i've never really needed to use this for iPhone views, more for iPad views, and even then for large forms only (e-commerce). So perhaps if you're not in that category, it might be worth reviewing your layout.
Another approach to this, is to use my approach, but to instead check for specific textFields right in the findActiveTextField() method if you only have a handful of textfields, and to animate things within findActiveTextField() as well if you know all of the possible positions they can be in.
Either way, i use inout parameters in this case, something worth looking into if you ask me.
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];