I want to display a UIAlertController whenever user opens the application.
This is how I'm creating and trying to show it:
import UIKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
//simple alert dialog
let alert=UIAlertController(title: "Alert 1", message: "One is awesome", preferredStyle: UIAlertControllerStyle.Alert);
//show it
showViewController(alert, sender: self);
}
}
Why is it not being displayed?
It will work if you'd use: presentViewController(alert, animated: true, completion: nil)
As #matt stated, it’s better to present your alertViewController in ViewDidAppear instead of ViewDidLoad, because than the presenting viewController is in the interface.
Too soon. In viewDidLoad, your view is not even in the interface yet! There is nothing to show from.
Related
I am dealing with a problem using UITabBarController. I have a small project using storyboards (XCode 13, IOS 15 as base system). I created a TabBarController but I later discovered I could not manage it effectively programmatically. Reading various docs, I discovered I could use two scenes from my storyboard and creating the tabbar programmatically.
So I did this in SceneDelegate.swift:
let queryViewControllerTab = storyBoard.instantiateViewController(withIdentifier: "QueryViewController")
let settingsViewControllerTab = storyBoard.instantiateViewController(withIdentifier: "SettingsViewController")
let starredViewControllerTab = storyBoard.instantiateViewController(withIdentifier: "StarredViewController")
starredViewControllerTab.tabBarItem.title = "Starred"
starredViewControllerTab.tabBarItem.image = UIImage(systemName: "star")
// TODO: Discover why first two views keep reading image I setup previously in storyboard
let tabBarController = UITabBarController()
tabBarController.viewControllers = [queryViewControllerTab, settingsViewControllerTab, starredViewControllerTab]
tabBarController.selectedViewController = settingsViewControllerTab
self.window?.rootViewController = tabBarController
self.window?.makeKeyAndVisible()
This works perfectly and I can easily put a condition whether userDefaults are not set, load directly the settings.
In my class SettingsViewController I want to add an action where, upon pressing the button, you get an alert:
#IBAction func saveButtonPressed(_ sender: UIButton) {
// keychain.set(tokenInput.text ?? "", forKey: keychainKey)
let alert = UIAlertController(title: "My Alert", message: "This is an alert.", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: NSLocalizedString("OK", comment: "Default action"),
style: .default, handler: { _ in
NSLog("The \"OK\" alert occured.")
}))
tabBarController.present(alert, animated: true, completion: nil)
}
But this makes the app crashing with unrecognized selector sent to instance 0x7f82f9705c30'
I've tried to debug the problem, and I understood I can't make the alert in this way because the view is really the tabBar and not the my scene. But here I got stuck.
I tried to implement the UITabBarControllerDelegate, in StarredViewController, but I can't get it working.
extension StarredViewController: UITabBarControllerDelegate {
func tabBarController(_ tabBarController: UITabBarController, didSelect viewController: UIViewController) {
print("did select tab bar item!")
}
}
I start thinking my main setup with SceneDelegate and AppDelegate is wrong.
Most of previous tutorials or threads I've found seems to fail even to compile because using deprecated versions.
This is a way to present an alert from any presented View Controller.
Add some extensions:
import UIKit
extension UIViewController {
var customVisibleViewController: UIViewController? {
if let navigationController = self as? UINavigationController {
return navigationController.topViewController?.customVisibleViewController
} else if let tabBarController = self as? UITabBarController {
return tabBarController.selectedViewController?.customVisibleViewController
} else if let presentedViewController = presentedViewController {
return presentedViewController.customVisibleViewController
} else if self is UIAlertController {
return nil
} else {
return self
}
}
}
extension UIApplication {
/// The top most view controller
static var topMostViewController: UIViewController? {
return UIApplication.shared.keyWindow?.rootViewController?.customVisibleViewController
}
}
Now you can show your alert in this way:
let alert = UIAlertController(title: "My Alert", message: "This is an alert.", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: NSLocalizedString("OK", comment: "Default action"),
style: .default, handler: { _ in
NSLog("The \"OK\" alert occured.")
}))
UIApplication.topMostViewController?.present(alert, animated: true, completion: nil)
This is the code to trigger an alert. With addAction, you can add possible answers.
do {
try //some method call or something else
} catch {
let alert = UIAlertController(title: "There was an error while saving!", message: "Please try again", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "I understand", style: .cancel, handler: nil))
}
you can find more information here:
how to show an alert
To get to the root Controller you can use the following code:
let viewController = UIApplication.shared.windows.first!.rootViewController as! YourViewController
I solved the problem. Actually, all my assumptions and the question were wrong.
TL;DR the storyboard is corrupted or got damaged when I removed the tab bar from it to make it programmatically.
Here the long version. Before entering in this trouble, I had a storyboard with two views and a tab bar controller. It was working perfectly. At one point, I decided I wanted to make a choice during the app starting and, in case of missing defaults, load immediately the settings view. I found that, to do this, I had to move my tab bar down to the scene delegate and remove it from storyboards. I did it, so storyboard was showing to views no linked, and I instantiated the tab bar from the scene delegate.
Weirdly, the tab bar being rendered was still showing some properties previously set on the storyboard, even if that component was deleted.
Then, you know the problem. My reasoning did not make any sense. The UITabBarController can't show any alert. Alerts can be presented on a UIViewController only. So, it was pointless to keep trying to make an alert out from a tab bar.
This wrong understanding led me also to wrong research which reported various similar questions (probably misleading).
I finally made a counter test. Created a brand new project with storyboard. Created two views on the storyboard and defined a tab bar controller on the scene delegate. It worked as expected. I linked each view to a specific UIViewController. Created a button on the view, added the IBAction and it worked. Then, I created the alert in the IBAction and, this time, worked exactly.
I ended with the same code, and the only different is that I did not create and removed a tab bar from the storyboard.
I knew that storyboard can get damaged and, probably, I did it.
I have a ViewControllerA that already show as pop out,which is present modally. Inside this ViewControllerA have a tableview with tableViewCell .So in each cell have a button.When users click on this button,I want to show actionSheet at the bottom of the screen.
Here is my code:
TableViewCell class,here I connect the button to the IBAction
protocol MyDelegate: class {
func showDropDownMenu()
}
class tableCell: UITableViewCell {
weak var delegate: MyDelegate?
#IBAction func dropDownButton(_ sender: Any) {
print("print something")
self.delegate?.showDropDownMenu()
}
}
ViewControllerA
class ViewControllerA: UIViewController , UITableViewDataSource, UITableViewDelegate,MyDelegate {
func showDropDownMenu() {
let actionSheet = UIAlertController(title: nil, message: nil, preferredStyle: .actionSheet)
// Create your actions - take a look at different style attributes
let hideAction = UIAlertAction(title: "Hide", style: .default) { (action) in
print("didPress hide")
}
let cancelAction = UIAlertAction(title: "Cancel", style: .cancel) { (action) in
print("didPress cancel")
}
actionSheet.addAction(hideAction)
actionSheet.addAction(cancelAction)
self.present(actionSheet, animated: true, completion: nil)
}
Suppose when click on the button will call the function showDropDownMenu() in ViewControllerA.Now I click on dropDownButton it will show print something in console(means no problem with the button),but the actionSheet not show up on the bottom.
I not sure what is the problem here,but I suspect is cause by ViewControllerA is present using segue with properties like so:
Kind: Present modally ,Presentation: Over Current Context ,Transition:
Cover Vertical
If this is the reason,please help me how to present an actionsheet from a View Controller that presented modally. Thank you
Code for showing ViewControllerA :
func showViewControllerA(Id: Int) {
self.performSegue(withIdentifier: "showViewControllerA", sender: Id)
}
Refer this link. Though it's for IPad, it will give you a brief idea of where and how to present the action sheet
https://medium.com/#nickmeehan/actionsheet-popover-on-ipad-in-swift-5768dfa82094
I have faced a similar scenario of what you are trying to achive, and this solution which i provided above helped me out. Hope, it helps you out as Well.
Make sure you have set value for delegate. For example
cell.delegate = self;
This question already has answers here:
dismiss share extension custom viewcontroller
(2 answers)
Closed 4 years ago.
So I have an app and a share extension. For the share extension I have just one simple controller that extends UIViewController and not SLComposeServiceViewController (I believe the default view is too complicated for what I am trying to do). What i'm trying to achieve inside the extension is to get some data from UserDefaults, make some HTTP requests and show an alert with the HTTP response. The share extension should only be used inside a browser, but after I tap the extension the browser view freezes and after I dismiss the alert the browser is still frozen. How and where I should dismiss the alert or the parent view?
I'm new to this environment but I did some research and I believe this has something to do with the view hierarchy but I'm not sure, here is the controller:
class ShareViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewWillAppear(_ animated: Bool) {
}
override func viewDidAppear(_ animated: Bool) {
let alert = UIAlertController(title: "Notification", message: "message", preferredStyle: UIAlertControllerStyle.alert)
alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.default, handler: nil))
self.present(alert, animated: true, completion: nil)
}
}
It's a duplicate and I'm not sure if I should answer here as well. Sorry for not searching enough. For swift 3:
self.extensionContext!.completeRequest(returningItems: nil, completionHandler: nil)
I have got a UIAlertController that I would like to present within a UITableViewController. However when I run the code I get the following error:
Warning: Attempt to present on
whose view is not in the
window hierarchy!
My code seem to reflect what suggested in this answer. What am I doing wrong?
override func viewDidLoad() {
super.viewDidLoad()
// Check for force touch feature, and add force touch/previewing capability.
if traitCollection.forceTouchCapability == .available {
registerForPreviewing(with: self, sourceView: view)
}
else {
// Create an alert to display to the user.
alertController = UIAlertController(title: "3D Touch Not Available", message: "Unsupported device.", preferredStyle: .alert)
self.present(alertController!, animated: false, completion: nil)
}
Suppose, in viewDidLoad you still don't have a view in the window hierarchy, like said in message. Try to move your code to viewDidAppear instead
I perform a segue from scene 1 to scene 2. I then return from scene 2 to scene 1. How do I not only pass data from scene 2 to scene 1 but detect in scene 1 that I've returned from scene 2 and execute code in scene 1?
In Android I do this with startActivity and onActivityResult.
Introducing Bool state like the other answer's suggesting is very bad and must be avoided if possible as it greatly increases the complexity of your app.
Amongst many other patterns, easiest one to solve this kind of problem is by passing delegate object to Controller2.
protocol Controller2Delegate {
func controller2DidReturn()
}
class Controller1: Controller2Delegate {
func controller2DidReturn() {
// your code.
}
func prepareForSegue(...) {
// get controller2 instance
controller2.delegate = self
}
}
class Controller2 {
var delegate: Controller2Delegate!
func done() {
// dismiss viewcontroller
delegate.controller2DidReturn()
}
}
States are evil and is the single biggest source of software bugs.
you could do it like this:
class SourceViewController: UIViewController {
var didReturnFromDestinationViewController = false
#IBAction func returnToSourceViewController(segue: UIStoryboardSegue) {
didReturnFromDestinationViewController = true
}
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
if didReturnFromDestinationViewController == true {
// reset the value
didReturnFromDestinationViewController = false
// do whatever you want
}
}
}
The problem I was having was that I was trying to show an alert dialog after the unwind segue had finished. So my View Controller 2 performed an unwind segue to View Controller 1. What I found is that the code that runs after the unwind segue method is called runs before View Controller 2 is dismissed, so when I tried to show an alert dialog, it would disappear as soon as View Controller 2 was dismissed.
If the other solutions don't work for you, do what I did. I added a viewWillAppear override to my class and dismissed the parent controller there, then added the code for my alert dialog after that. To make sure viewWillAppear wasn't showing the alert dialog the first time View Controller 1 was presented, I set up an if statement checking for the name of a variable that I declared in the class and had set equal to "". Then in View Controller 2 I passed some text in the variable back to View Controller 1, so when the if statement runs it tests the variable not equal to "", and when it finds it's not, the code is run. In my case the variable was named "firstname".
override func viewWillAppear(_ animated: Bool) {
if firstname != "" {
self.parent?.dismiss(animated: true, completion: nil)
//CustomViewController?.dismiss(animated: true, completion: nil)
let alertController = UIAlertController(title: "Hello", message: "This is a test", preferredStyle: .alert)
let defaultAction = UIAlertAction(title: "Close Alert", style: .default, handler: nil)
alertController.addAction(defaultAction)
present(alertController, animated: true, completion: nil)
}
}