I want to show user a message once.
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
let defaultsDatafirstTrue = NSUserDefaults.standardUserDefaults()
if let _ = defaultsDatafirstTrue.stringForKey("firstTrue") {
} else {
let alertController = UIAlertController(title: "You can add road markers just do long press on the Map", message: "", preferredStyle: .Alert)
let OKAction = UIAlertAction(title: "OK", style: .Default) { (action:UIAlertAction) in
}
alertController.addAction(OKAction)
self.presentViewController(alertController, animated: true, completion:nil)
defaultsDatafirstTrue.setObject("true", forKey: "firstTrue")
}
}
But I have error Warning: Attempt to present <UIAlertController: 0x7c2a8000> on <****: 0x7d193800> whose view is not in the window hierarchy! Because at the first run the iOS app displays a warning to the user that will use the location determination.
How can I see my message after the system message?
Run the code from viewDidAppear: not from viewWillAppear:.
The problem with viewWillAppear: is that it is called before the view is actually visible, so you cannot present another view from it yet. Also, viewWillAppear: can be actually called multiple times and then cancelled (e.g. for interactive transitions).
Related
I have a register screen in my app, after the user writes done a phone number and agrees to the terms, and clicking "register" the app should move the user to the next vc. The problem is, although everything looks to be ok, the app won't move to the next screen.
This is my code:
func handleRegister() {
if UserDefaults.standard.object(forKey: USER_AGREED) == nil {
let alert = UIAlertController(title: "Terms and Conditions", message: "Please agree to the terms and conditions to continue", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: { (alert) in
self.showTermsAndConditions()
}))
alert.addAction(UIAlertAction(title: "Cancel", style: .destructive, handler: nil))
self.present(alert, animated: true)
}else{
guard let userPhoneNumber = self.mView.textField.text else { return }
UserDefaults.standard.set(userPhoneNumber, forKey: USER_PHONE_NUMBER)
let vc = Tabbar()
self.navigationController?.pushViewController(vc, animated: true)
}
}
I tried to put a breakpoint, and it does gets to the else block when it should, and recognizes the Tabbar, but just won't move there.
Any suggestions?
There are two possible sources of trouble here.
You are saying self.navigationController?. The question mark means: "If I have no navigationController, do nothing." If you have no navigationController, you do nothing. Perhaps what you meant to say is self.present(vc, animated:true).
You are saying let vc = Tabbar(). That is not an existing view controller in the interface or storyboard. So when you move there, it might be empty (that depends on how Tabbar view controller is constructed).
I have this alert controller setup to appear as soon as the view controller is loaded. However, it does not appear.
I believe I have all the facets covered - title, message, alert style, action button and present... but still does not appear.
Unsure what I'm missing.
let array = quoteBank()
print(array.sarcasticQuotes[0].quote)
let title = "Message"
let message = array.sarcasticQuotes[0].quote
let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
alert.addAction(.init(title: "OK", style: .default, handler: nil))
present(alert, animated: true, completion: nil)
Attempting to show an alert in viewDidLoad is too soon. The view controller isn't displayed yet. Use viewDidAppear.
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
// Use this if statement to only show the alert once
if self.isBeingPresented || self.isMovingToParentViewController {
// show your alert here
}
}
You need to perform that on the main thread:
DispatchQueue.main.async {
present(alert, animated: true, completion: nil)
}
The reason behind that is that the view controller's hierarchy will be set after viewDidLoad is finished. So by doing this, you're scheduling the presentation of the alert on the main thread to the time the main thread is finished from executing viewDidLoad.
Trying to figure out why I am getting this error. I have a single view application with two viewcontrollers. I have a segue to the second vc on a button touch:
#IBAction func showAccount(_ sender: Any) {
performSegue(withIdentifier: "toAccountFromRoot", sender: self)
}
I have a facade pattern set up with a Controller file and several helper files. I set the Controller up on the AccountViewController file:
let myController = Controller.sharedInstance
One of the helper files is to set up a central AlertController for simplified alerts (no extra buttons). It has one method, presentAlert that takes a few arguments, alert title, messsage, presenter.
On my AccountViewController I am attempting to present an alert using this code:
myController.alert.presentAlert("No Agent", "You have not registered an agent yet.", self)
and in the AlertManager file, presentAlert looks like this:
func presentAlert(_ title:String, _ message:String, _ presenter:UIViewController) {
let myAlert = UIAlertController(title: title, message: message, preferredStyle: .alert)
let okAction = UIAlertAction(title: "OK", style: .default, handler: nil)
myAlert.addAction(okAction)
presenter.present(myAlert, animated:true, completion:nil)
}
I've done this in quite a few apps without an issue so I am confused as to why the compiler thinks the AccountViewController view is not in the window hierarchy.
Dang it, typed all that and then I solved it 5 seconds later. Just in case someone else runs into the same problem, I was trying to present the alert in viewDidLoad, should of been doing it in viewDidAppear.
I'm new to Swift (and programming in general). I'm having some difficulties in Xcode with the login feature. What I want is that the user should be logged in if no errors was returned and the user should be sent to another controller. I've read some of the documentation from Apple and the performSegueWithIdentifier (and of course some questions asked here), but it still does not work when I use a segue with push or modal that are given an identifier. Either the app crashes, or the user is sent to my UITabBarController even if the credentials was incorrect.
This is my LogInViewController.swift:
#IBAction func loginAction(sender: AnyObject)
{
if self.emailField.text == "" || self.passwordField.text == ""
{
let alertController = UIAlertController(title: "Oops!", message: "Please enter an email and password.", preferredStyle: .Alert)
let defaultAction = UIAlertAction(title: "OK", style: .Cancel, handler: nil)
alertController.addAction(defaultAction)
self.presentViewController(alertController, animated: true, completion: nil)
}
else
{
FIRAuth.auth()?.signInWithEmail(self.emailField.text!, password: self.passwordField.text!) { (user, error) in
if error == nil
{
self.emailField.text = ""
self.passwordField.text = ""
}
else
{
let alertController = UIAlertController(title: "Oops!", message: error?.localizedDescription, preferredStyle: .Alert)
let defaultAction = UIAlertAction(title: "OK", style: .Cancel, handler: nil)
alertController.addAction(defaultAction)
self.presentViewController(alertController, animated: true, completion: nil)
}
// User Logged in
self.performSegueWithIdentifier("LoggedIn", sender: self)
}
}
}
The error I get in the console:
2016-09-04 14:55:30.019 DrinkApp[37777:1006336] *** Terminating app due to uncaught exception 'NSGenericException', reason: 'Could not find a navigation controller for segue 'LoggedIn'. Push segues can only be used when the source controller is managed by an instance of UINavigationController.'
There are two main ways to send a user to another View Controller. The first is performSegueWithIdentifier. Here's how you would go about using that:
First of all, control-drag from the yellow circle of the original VC to the target VC in the interface builder.
Next, click on the 'segue arrow' that appears between the two View Controllers.
In the identifier field, type in mySegue.
Next, go back to your code. When you reach the sign in section, add the following code:
self.performSegueWithIdentifier("mySegue", sender: nil)
The second method is a bit more advanced. Here's how that would work:
First, click on the yellow circle of the destination VC. Click on the newspaper, then call the storyboard ID myVC.
Make sure to click on Storyboard ID
Go back to the same part of the code and copy and paste this code:
let storyboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
let initViewController: UIViewController = storyboard.instantiateViewControllerWithIdentifier("myVC") as UIViewController
self.presentViewController(initViewController, animated: true, completion: nil)
Comment down below if you have any questions. Good luck!
Here is a Firebase login example:
func login() {
FIRAuth.auth()?.signInWithEmail(textFieldLoginEmail.text!, password: textFieldLoginPassword.text!) { (user, error) in
if error != nil {
let alert = UIAlertController(title: "User Authentication error",
message: error?.localizedDescription,
preferredStyle: .Alert)
let OKAction = UIAlertAction(title: "OK",
style: .Default) { (action: UIAlertAction!) -> Void in
}
let resetPasswordAction = UIAlertAction(title: "OK",
style: .Default) { (action: UIAlertAction!) -> Void in
}
alert.addAction(OKAction)
guard let errorCode = FIRAuthErrorCode(rawValue: (error?.code)!) else { return }
switch errorCode {
case .ErrorCodeWrongPassword:
alert.addAction(resetPasswordAction)
case .ErrorCodeNetworkError:
print("Network error")
default:
print("Other error\n")
break
}
self.presentViewController(alert, animated: true, completion: nil)
} else { // User Logged in
self.performSegueWithIdentifier("MySegue", sender: self)
}
}
}
I only handled two errors for this example.
If you use push segue, you need to have navigation controller, and your root segue should lead to the login view controller, then another segue to the next view controller. This last segue must have an identifier (in this case it's MySegue)
Edit:
Since it seems that your problem is not with Firebase, but with setting up the storyboard. Here is an example:
Set up one UINavigationController two UIViewControllers
Control Drag between the UINavigationController to the middle UIViewControllers and choose root view controller from the popup menu
Control Drag between the UIViewController to the last UIViewControllers and choose show
select the segue added in the previous step and change its identifier (in the attributes inspector) to MySegue.
5.Choose the Middle UIViewControllers and change the class name (in the identity inspector) to your login view controller class.
Here is the full setup:
control drag menu (step 2):
Segue attributes inspector (step 4):
I found this answer mentioned here to be super elegant.
https://fluffy.es/how-to-transition-from-login-screen-to-tab-bar-controller/
it works with tab bars, and nav bars. you create a function in the scene delegate, that switches the root view controller. you access the scene delgates functions and windows with (UIApplication.shared.connectedScenes.first?.delegate as? SceneDelegate)?
I'm trying to figure out is how to create a pop up window that only appears once when you start the app and then won't appear again unless you close the app and reboot it. However, if you view the code below, you will realize that the alert will pop up every time the ViewController appears. For example, if you go to the settings tab and then return to the main ViewController, then the alert will pop up.
override func viewDidAppear(animated: Bool) {
let alertController = UIAlertController(title: "Disclaimer", message: "WARNING: Please ride carefully!", preferredStyle: UIAlertControllerStyle.Alert)
alertController.addAction(UIAlertAction(title: "Accept", style: UIAlertActionStyle.Default, handler: nil))
self.presentViewController(alertController, animated: true, completion: nil)
}
Just create a global variable that is a Bool. If the app is opened it starts at false. Then once the disclaimer is seen it sets the variable to true. Then present the View Controller based on the value of the variable.
var disclaimerHasBeenDisplayed = false
class ViewController {
override func viewDidAppear(animated: Bool) {
if disclaimerHasBeenDisplayed == false {
disclaimerHasBeenDisplayed = true
let alertController = UIAlertController(title: "Disclaimer", message: "WARNING: Wakeboarding is fun, however it can be highly dangerous.
Wake Dice is not liable for any injuries obtained while wakeboarding. Please ride carefully!", preferredStyle: UIAlertControllerStyle.Alert)
alertController.addAction(UIAlertAction(title: "Accept", style: UIAlertActionStyle.Default,handler: nil))
self.presentViewController(alertController, animated: true, completion: nil)
}
}
}