I have implemented SWRevealViewController class for revealing a rear (left and/or right) view controller behind a front controller. SWRevealViewController of type UIViewController is the entry point in the app.
What do I want?
In class AppDelegate when applicationDidEnterBackground is called, I want to pop all the view controllers on the stack except the root view controller and updates the display.
What I tried?
if let appDelegate = UIApplication.shared.delegate as? AppDelegate {
appDelegate.window?.rootViewController?.dismiss(animated: true, completion: nil)
}
I know that if SWRevealViewController were embedded in a UINavigationController, I could simply do (appDelegate.window?.rootViewController as? UINavigationController)?.popToRootViewController(animated: true) , but it is not embedded in nav controller and if I embed it, then I will not get the same behaviour, so how can I sort this out?
I believe what you are trying to do is an "unwindSegue".
They are are documented in a technical note:
https://developer.apple.com/library/content/technotes/tn2298/_index.html
With that you should be able to identify your root view controller as the target of the unwind segue and, of needed, follow the unwind through various steps as it occurs.
You can also look at the documentation for the various methods of UIViewController that contain the term "unwind"
https://developer.apple.com/documentation/uikit/uiviewcontroller
Try This:
let navVC = ((UIApplication.shared.delegate as? AppDelegate)?.window)?.rootViewController as? UINavigationController
for VC: UIViewController in (navVC?.viewControllers)! {
if (VC is MYViewController) {
navVC?.popToViewController(VC, animated: true)
break
}
}
Related
I am trying to understand relationship between UINavigationController and UIViewController.
According to apple documentation
A container view controller that defines a stack-based scheme for navigating hierarchical content.
When I open UIKit and UINavigationController class there are some properties which I could not imagine, how they is written by Apple.
UINavigationController : UIViewController { }
so UINavigationController subclass of the UIViewController and inherit its properties.
then what about these properties in this extension ? These ones inherits from a protocol which I could not see in UIKit. Could you explain a little bit please ?
extension UIViewController {
open var navigationItem: UINavigationItem { get } // Created on-demand so that a view controller may customize its navigation appearance.
open var hidesBottomBarWhenPushed: Bool // If YES, then when this view controller is pushed into a controller hierarchy with a bottom bar (like a tab bar), the bottom bar will slide out. Default is NO.
open var navigationController: UINavigationController? { get } // If this view controller has been pushed onto a navigation controller, return it.
}
I am not sure what you need to understand but i will assume that it's why those properties are there and exposed for the UINavigationController.
As the definition address it UINavigationController is a basically a stack of UIViewControllers, that uses, push, pop functions to add and remove to the stack here is more about how stack works.
for the relationship, it's clear that's every UINavigationController is inheriting a UIViewController but it's tricky because you are thinking why? since it hold a UIViewController why it inherits from it the answer rely on the usage this allows us to have multiple navigations embedded in each others so a navigation controller can hold another navigation controller inside of it, that's why you see those properties so in a scenario you can have the following stack and those properties are there if you need to use them on the UINavigationController it self as it gets pushed.
let firstVC = UIViewController()
let secondVC = UIViewController()
let firstNav = UINavigationController(rootViewController: firstVC)
let secondNav = UINavigationController(rootViewController: secondVC)
firstNav.hidesBottomBarWhenPushed = true
let thirdNav = UINavigationController(rootViewController: firstNav)
thirdNav.pushViewController(secondNav, animated: false)
My app has a TabBarController. Each tabBarItem relates to a ViewController embedded in a NavigationController.
When in first tabBarItem and selecting another tabBarItem I want to do some stuff before moving to the selected ViewController. Therefore I created a class for my tabBarController and made it UITabBarControllerDelegate.
What I want to do is present an alert with two buttons; button A cancels the move to the selected viewController and button B lets the move happen.
My problem is that when button B is pressed, I want to popToRootViewController. I gave the navigationController a storyboardID and tried to instantiate it like shown below.
func tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController) -> Bool {
if let alert = self.storyboard?.instantiateViewController(withIdentifier: "ActiveSessionWarningAlert") as? ActiveSessionWarningAlert {
alert.modalPresentationStyle = UIModalPresentationStyle.overCurrentContext
alert.modalTransitionStyle = UIModalTransitionStyle.flipHorizontal
let alertWasDismissed: (Bool) -> Void = { userWantsToMoveToSelectedViewController in
if userWantsToMoveToSelectedViewController {
if let navContr = self.storyboard?.instantiateViewController(withIdentifier: "firstNavContr") as? UINavigationController {
navContr.popToRootViewController(animated: true)
}
tabBarController.selectedViewController = viewController
}
}
alert.alertWasDismissed = alertWasDismissed
self.present(alert, animated: true, completion: nil)
}
return false
}
Everything works as expected, but the popToRootViewController doesn't seem to occur; when selecting the first tabBarItem again the same viewController that was 'active' when we left the item is still showing.
I checked so that the viewController I want to pop is actually in the navigation stack and that the navContr != nil.
What am I missing?
You don't say so, but I'm assuming that the alertWasDismissed closure you pass to your alert view controller gets invoked when the user dismisses the alert.
The problem with your closure is this bit:
if let navContr = self.storyboard?.instantiateViewController(withIdentifier: "firstNavContr") as? UINavigationController
Any time you call instantiateViewController(withIdentifier:), you are creating a brand new, never before seen instance of a view controller (a navigation controller in this case.) That navigation controller has nothing to do with the one that belongs to the current tab that you are trying to dismiss. It doesn't have anything in it's navigation stack other than the root view controller that is defined in the storyboard.
What you need to do is find the navigation controller of the current tab in your tab bar controller's tabBarController(_:shouldSelect:) method, and pass that navigation controller to your alertWasDismissed closure.
At the time the tabBarController(_:shouldSelect:) method is called, the tab bar controller's selectedViewController should contain the current view controller. Replace the line above with:
if let navContr = tabBarController.selectedViewController? as? UINavigationController {}
That should work.
Having some trouble permanently moving one from view controller to another. The normal segues seem to all have a 'go back' option.
I know I can imbed the VC in a navigation controller and create a custom segue which rewrites the hierarchy/changes root VC
class ReplaceSegue: UIStoryboardSegue {
override func perform() {
source.navigationController?.setViewControllers([self.destination], animated: false)
}
}
But I want to avoid a navigation controller as it will confuse things when I add a SWRevealViewController later.
Can/Should I change the storyboard VC (outside of AppDelegate that is)?
Thanks - apologies if this is a 'beginner' question
You can either change rootViewController of your main window:
self.window.rootViewController = vc
or you can just simply set vc's modalPresentationStyle to fullscreen (this doesn't have a "go back" option by itself, only you can dismiss it calling dismiss)
let vc = UIViewController()
vc.modalPresentationStyle = .fullScreen
or from storyboard change it's presentation style to fullscreen.
I am proudly new to iOS developing and I am trying to build my first app. I am doing a course on an online platform which does the following in the
AppDelegate -> application didFinishLaunchingWithOptions:
let navigationController = window?.rootViewController as! UINavigationController
let notebooksListViewController = navigationController.topViewController as! NotebooksListViewController
notebooksListViewController.dataController = dataController
This app has a Navigation controller which begins with an UIViewController.
I have 2 questions here, first is why this works, I mean, I am in AppDelegate, so the NotebooksListViewController (first view of the app) is not instantiated yet (I think), so why I am able to inject a variable in it?
On the other hand, the second question, is how can I do this in a different scene? I have a TabBarViewController as first scene, and the first tab is a UITableViewController and I want to inject the same way my dataController var, how can I accomplish this? I could not get to do it, neither understand it.
Thanks in advance.
It works, because of some Xcode magic:
In your Target Setting, General tab, the Main Interface entry specifies the name of the Storyboard to be loaded automatically when your app starts up:
In the storyboard, the Initial View Controller then will be instantiated. It seems like this is an UINavigationController.
Since this is done automatically, it just works - until you want to do something special :-)
If you want to start up with a different scene - maybe from a different view controller - you could just change either the Main Interface to another storyboard, the Initial View Controller (inside the storyboard) or both.
Or, you could just start up by yourself, by leaving the Main Interface empty and create your own view controller inside the app delegate (didFinishLaunchingWithOptions), something like
self.window = UIWindow(frame: UIScreen.mainScreen().bounds)
let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
if let tabVC = mainStoryboard.instantiateViewControllerWithIdentifier("TabCtrl") as? UITabBarController {
self.window?.rootViewController = tabVC
// Access the subcontrollers, or create them
// Initialize their values
// tabVC.viewControllers[0].data = ...
} else {
// Ooops
}
self.window?.makeKeyAndVisible()
Answer to your first question
as the method name is self explanatory didFinishLaunchingWithOptions means your application is didfinish with launching with options and its about to enter in foreground so here application need to set rootViewController so in this method controller you want to set as view controller is initiated thats why you can inject variable in it
answer to second question
let navigationController = window?.rootViewController as! UITabbarController
let VC = navigationController.childViewController
//Now Using VC you can access all you controller of tabbar controller
let notebooksListViewController = navigationController.topViewController as!
NotebooksListViewController
notebooksListViewController.dataController = dataController
now as shown above you can use VC to access you view controllers
but be careful here because VC return viewcontroller array so you need make checks for perticular VC you want to access
I have an app written in swift that displays location information on different views. I am receiving location updates in AppDelegate (I don't want to use a singleton class since I want the location updates even when the app is in the background).
Now, I am using SWRevealViewController to implement a sidebar menu to toggle between the different views. When a new location update is received, how do I call the function of the viewController that is currently active to update the UI?
I searched a lot and all the solutions that talk about how to find the current UIViewController actually return SWRevealViewController as the current UIViewController, which doesn't help.
I gave it another shot and was able to find my viewController in my app from another view controller. However, I couldn't get my child view controllers app delegate.
Looking forward to other answers...
here's what I did:
let app = UIApplication.sharedApplication().delegate! as! AppDelegate
if let nav = app.window?.rootViewController?.childViewControllers {
nav.forEach { vc in
if let viewControllers = vc as? UINavigationController {
viewControllers.childViewControllers.forEach { vc in
if let x = vc as? ViewController {
print("Got it \(x)")
}
}
}
}
}