I'm trying to get the currently displayed ViewController using the following:
let currentViewController = UIApplication.sharedApplication().keyWindow!.rootViewController?.presentedViewController
This property gives me the TabBarController. The only property after presentedViewController is "childViewControllers".
How could I use this to attain the currently displayed ViewController?
If it is TabBar based Application then to check which is currently selected ViewController depends on following condition :
First Track which tabbar is selected e.g :Condition to check which Tab Index is selected
Maintain NavigationController for each TabBar
Then Check navigationcontroller stack last index to match up the ViewController . ( which is chilviewcontroller you can say).
Hope it helps .
You can access the selected view controller from the tabBarController. An easy way to do so is with this extension.
Just take note that it will not update with the correct value until viewDidAppear. Checking the property prior to that will give you your previous screen.
import UIKit
extension UITabBarController {
var displayedViewController: UIViewController? {
return selectedViewController
}
}
Related
I have a tabBar in my app. I want to display a badge with a number of unread messages when notification comes. So far my code is below.
The problem is that the messages tab isn't always the first item in the list (the order varies for different app settings, but it's always there). How do I set the badge on it if I don't know which index it has?
if let item = self.tabBar.items?.first {
var count = messages.count
if item.badgeValue != nil {
count += Int(item.badgeValue!) ?? 0
}
item.badgeValue = "\(count)"
}
You are getting first item in first line - so it's working as expected.
You need to organize your UITabBar this way, that you can always identify on which index messages are presented.
One idea would be to keep a reference to it when you configure your UITabBar - this way that you can always find under which index messages are shown.
Best way would be to keep corresponding array of views you keep behind your UITabBar, and then find the one you need.
If you are using UITabBarController you will get it for free - all UIViewController are accessible directly via property named viewControllers.
If you have custom ViewController and just UITabBar - you just need to build similar logic that will allow you to keep track on which index certain view controller is shown.
Assuming your tabbar is managed by a UITabBarController, you can determine the index by checking the type of the view controllers in your tab bar controller.
class MessagesViewController: UIViewController {
// ... your messages vc
}
if let index = tabbarController.viewControllers?.firstIndex(where: { $0 is MessagesViewController }) {
tabbarController.tabBar.items?[index].badgeValue = "..."
}
I'm new with IOS and Swift so don't judge if solution is easy.
I have three ViewControllers like A,B and C.
I started from A -> NavigationController -> B -> NavigationController -> C
In specific situation I need to come back from C to A without seeing B. Is any way to do this?
Maybe changing the parent navigationController? Maybe I can print stack with every current view? - it will be really helpful.
I tried dismiss C and B view one by one and it work's but then we can see B view for a moment - so it's not a solution for me.
P.s : I'm using Modal kind to switch between controllers.
enter image description here
If A is always the first view controller, you can just do :
viewcontrollerC.navigationController?.popToRootViewController(animated: true)
This methods pop the stack to the first view controller, without displaying intermediates ones
If A is not the first viewController, you can do :
viewcontrollerC.navigationController?. popToViewController(viewControllerA, animated: true)
If you don't have a reference to viewControllerA, search it in the stack :
let viewControllerA: UIViewController?
for (let vc in (self.navigationController?.viewControllers ?? [])) {
//adust the test to find the appropriate controller
if vc.isKindOf(ViewControllerAClass.self) {
viewControllerA = vc
break
}
}
if let viewControllerA = viewControllerA {
self.navigationController?.popToViewController(viewControllerA, animated: true)
}
source : https://developer.apple.com/documentation/uikit/uinavigationcontroller/1621871-poptoviewcontroller
There are 2 ways you can achieve this. The simple to implement is in View Controller C you can, on in the specific situation, invoke following function:
navigationController?.popToRootViewController(animated: true)
This will pop all the navigational view hierarchy and take you back to the root i.e. the first view controller.
Second approach is to define unwind method in the view controller you want to go back to. In view controller when you start typing unwind, in Xcode 10 you will get autocomplete to add this Swift Unwind Segue Method.
#IBAction func unwindToA(_ unwindSegue: UIStoryboardSegue) {
let sourceViewController = unwindSegue.source
// Use data from the view controller which initiated the unwind segue
}
In this particular question let us say you added this method in View Controller A as you want to go back to it. I assume you have a button on View Controller C to go back to A. Controll+Drag from the button to the Exit symbol of the view controller A. The unwindToA method will automatically pop-up. Connect to it and you are done. When the user presses this button it will go back 2 navigation controllers to A.
Note: By this method you can go back to any navigation controller on the Navigation stack and it is not limited to root view controller alone. Below I am addition picture showing the exit on a view controller.
I am currently implementing the XLPagerTabStrip (https://github.com/xmartlabs/XLPagerTabStrip) which effectively creates a tab bar at the top of the view controller. I want to be able to segue to a new view controller from one of the tabbed controllers and be able to use the navigation bar to move backwards (or a custom version of the navigation bar if this isn't possible).
XLPagerTabStrip provides the moveToViewController and moveToViewControllerAtIndex functions to navigate between child view controllers, but this method doesn't allow use of a navigation bar to go backwards.
Conceptually XLPagerTabStrip is a collection of view controllers declared and initialized during the XLPagerTabStrip model creation.
It has virtually no sense to use a UINavigationController if you already have all the viewcontrollers available.
You can create a global var previousIndex to store the previous viewController index and allow users to go back by using canonical methods:
func moveToViewControllerAtIndex(index: Int)
func moveToViewControllerAtIndex(index: Int, animated: Bool)
func moveToViewController(viewController: UIViewController)
func moveToViewController(viewController: UIViewController, animated: Bool)
About a new viewController, suppose you have 4 viewControllers that built your container (XLPagerTabStrip) named for example z1, z2, z3 e z4.
You can embed to z4 a UINavigationController (so it have the z4 controller as rootViewController) and start to push or pop your external views. When you want to return to your z4 you can do popToRootViewControllerAnimated to your UINavigationController
When you are go back to z4 , here you can handle your global var previousIndex to moving inside XLPagerTabStrip.
I'm not familiar with XLPagerTabStrip, but I had a similar problem recently and the solution was to use an unwind segue to go back to the previous view controller. It's pretty trivial to implement so probably worth a try.
To navigate back to your previous view tab controller, you had initially navigated from;
Embed your new view controller, from which you wish to navigate
away from in a navigation bar
Connect it's Navigation Bar Button to the Parent view containing the
tab bar by dragging a segue between the 2 views
Create a global variable in App delegate to store current index
which you will use in the Parent view to determine what tab view
controller to be shown
var previousIndex: Int = 0 //0 being a random tab index I have chosen
In your new view controller's (the one you wish to segue from)
viewdidload function, create an instance of your global variable as
shown below and assign a value to represent a representative index
of the child tab bar view controller which houses it.
//Global variable instance to set tab index on segue
let appDelegate = UIApplication.shared.delegate as! AppDelegate
appDelegate.previousIndex = 2
You can write this for as many child-tab connected views as you wish, remembering to set the appropriate child-tab index you wish to segue back to
Now, create a class property to reference your global variable and a function in your Parent view as shown below
let appDelegatefetch = UIApplication.shared.delegate as! AppDelegate
The function
func moveToViewControllerAtIndex(){
if (appDelegatefetch.previousIndex == 1){
self.moveToViewControllerAtIndex((self.appDelegatefetch.previousIndex), animated: false)
} else if (appDelegatefetch.previousIndex == 2){
self.moveToViewControllerAtIndex((self.appDelegatefetch.previousIndex), animated: false)
}
}
You may now call this function in the Parent View Controller's viewDidLoad, as shown below.
moveToViewControllerAtIndex()
Run your project and that's it.
I want to pass data from one tabBar controller to another,
I am switching tabBar using tabBarController?.selectedIndex = 0
I tried many option but unable to pass data to another tab, is there any simple solution like we pass data using navigation controller?
Tabs are usually some custom UIViewControllers. From these view controllers (tabs) you can also get access to the UITabBarController with something like:
if let mainController = UIApplication.sharedApplication().delegate?.window??.rootViewController as? YourMainTabBarControllerClass {
mainController.someVariable = 123
}
Here you have to be careful, because the tab bar controller may not be the rootViewController, see this question for more details.
In order to store some properties in the UITabBarController you have to implement your own class by extending UITabBarController and then set the custom class in the StoryBoard. The class will then look like:
class YourMainTabBarControllerClass: UITabBarController {
// some custom variables here...
var someVariable = 0
...
}
My segue is returning with an error (unwrapping an optional value) from this line > self.navigationController?....
In my code...
let nextScreen = self.storyboard!.instantiateViewControllerWithIdentifier("onboarding-what") as? ViewController
self.navigationController?.pushViewController(nextScreen!, animated: true)
This above code is implemented in my onboarding-start view controller
This is my storyboard set up...
the last view controller has the id of "onboarding-what".
I've read the documentation for the navigation controller but can't seem to find my problem. Does anyone have a solution?
You can use performSegueWithIdentifier rather than pushViewController if you connected them in storyboard
However did you fill "onboarding-what" in the storyboardId field?
pls check this image
Also "onboarding-what" view controller should be instance of ViewController
(There's not default class called "ViewController" only "UIViewController" or "NSViewController" for osX.)
Obviously nextScreen is nil. It is most likely that "onboarding-what" identifier is incorrect