In my XCode project, which implements MultipeerConnectivity framework, I have a segue between two ViewControllers which is triggered programatically after MPCHandler successfully establishes connection with another peer. After segue is performed, the destination VC appears being completely blank (all white). However, if I try to access the destination VC with help of a button (with segue dragged directly from the button to the destination VC), it appears as it should.
Here is the line of code, which performs the segue:
performSegueWithIdentifier("seg_wait", sender: self)
So, yeah, I know how to perform segues and, yes, I made sure identifier is unique and is the same as in storyboard. I had tons of segues in many of my projects, and that's the first time I've faced a problem like this. Did anyone face a problem like this? Any ideas on how to solve it?
UI updates always have to be done on the main thread ("the law"). So try to wrap the call:
dispatch_async(dispatch_get_main_queue(), {
performSegueWithIdentifier("seg_wait", sender: self)
})
Related
I've read several posts on this issue but none of them solved my problem.
I'm coding an app where I have to click on a button ("Prepare") to go to the following ViewController. When the button is clicked, it also passes data between the two view controller.
The problem is, when I click the button, the following ViewController loads twice. Thus, if I want to go back I have to go back through two same ViewController.
I've checked the segue, the class names and files names but nothing fixes it.
I've also created a new project and rewritten all the code from the beginning but in the end, it still doesn't work.
However, I've noticed that the problem showed up when I added the prepare(forSegue:) function and the performSegue function. Without it the ViewController only loads once. But of course, I can't get the data passed between the views without it...
Here is the screenshot of my two view and the code of the two functions :
First view
Second view
// Prepare the segue
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "prepareSegue" {
let timerViewController = segue.destination as! CountdownViewController
timerViewController.timeInterval1 = waitingTime
timerViewController.timeInterval2 = shootingTime
timerViewController.lastSeconds = lastSeconds
timerViewController.currentTimeInterval = waitingTime
}
}
// Prepare the timer when the button is pushed
#IBAction func prepareTimer(_ sender: Any) {
performSegue(withIdentifier: "prepareSegue", sender: self)
}
Probably, when two ViewControllers appear it's because you have:
A segue on Storyboard which start directly from a Button
IBAction attached to the button where you call a performSegue of the same Segue
To fix this problem, you need to create a Segue which start directly from ViewController. After you can use the IBAction and the performSegue
You have added a seague but also an IBAction. If the seague is defined well in InterfaceBuilder it will perform and call your method. The IBAction is the alternative way for connecting an Action to a button. If you use both, you have two actions.
Without the rest of your project to check, one thing it could be is a completion closure which contains the performSegue(...) statement is called twice, so the performSegue statement is literally run twice. How might this happen?
If you have a networking call inside the closure which contains performSegue command, and the networking call has a closure which calls completion(...) twice, then you could get either the segue occuring twice or even recursively!
It's rare this will be the case, or in your instance, but this type of problem can be uncovered by using lots of breakpoints and following the "bouncing ball" to see the completion() calls occuring more than once.
I am trying to implement a segue programmatically in IOS.
My story board looks like this:
The first segue between the first two screens is done by connecting the Login button to the next screen (so not completely programmatically), and it works fine.
The issue is with the "secondSegue", which I tried doing programmatically.
It simply does not work and there is no error message appearing.
I connected the 'Load this Screen' button to the following action in the Second Screen's view controller:
#IBAction func openThirdScreen(_ sender: Any) {
performSegue(withIdentifier: "secondSegue", sender: nil)
}
But the screen isn't opening and there is no error.
All the proper IBOutlets seem connected so I don't know what the issue could be.
I put a print statement in openThirdScreen(), and it prints, but a print statement in the third screen's View Controller's viewDidLoad() does not print, even though
I made sure the third screen was connected to a view controller.
I had overridden performSegue() earlier in order to do more with the segue but it was not working so I removed it for simplicity.
Please let me know what I messed up.
Sorry if this is a stupid question, I'm very new to XCode and I couldn't find anyone online with the same issue.
Let me know if there are more screenshots that are necessary to answer my question.
Edit: the following image was requested, in order to answer the question
I am use to performing unwinds to the easy what that is like this:
First set this on the destination view controller:
#IBAction func unwindToThisViewController(segue: UIStoryboardSegue) {}
Finally drag and drop and then pick the wanted unwind:
But till Xcode updates to 8.2.1 if you have the destination view controller with some extensions it doesn't appear on the list (Manual Segue). I didn't update to 8.3 because I'm still using Swift 2.3 so I don't know in further versions this bug is solved.
Instead of having to move all the extensions in the same file, which it will be a chaos find anything there. I am wondering if there is any other way to perform this action without using the storyboard step.
I am currently using navigation controller, maybe popToViewController will do it? I don't know honestly.
Thank you very much for the help.
In the storyboard, give your unwind segue an identifier.
Then, in your code do:
performSegue(withIdentifier: "SegueID", sender: nil)
Source: https://spin.atomicobject.com/2014/12/01/program-ios-unwind-segue/
I ran into an issue where I had the following setup, but was unable to get an unwind segue to work.
The storyboards were created several months ago, and were refactored from an original main storyboard to split them out into individual ones, with each storyboard having a single view controller.
The storyboards:
MainMenu.storyboard (Contains the navigation controller)
SubMenu.storyboard (Contains the segue that sends the user to the destination storyboard)
Destination.storyboard (Should contain unwind segue)
In the SubMenu viewcontroller, I have the following unwind segue:
#IBAction func unwindToSubMenu(segue: UIStoryboardSegue) {}
I then place a bar button item on the navigation item for the destination view controller. Attempting to link the bar button item to the exit icon on the Destination.storyboard file does not result in the unwindToSubMenu segue appearing.
Also, right clicking on the exit icon results in an empty field.
I did attempt to move the Destination.storyboard contents back to the SubMenu.storyboard to see if it had something to do with the reference links, but this was unsuccessful.
Updated with a better answer.
I ran into this problem again using the latest version of XCode (8.2.1) where a properly configured segue was not appearing.
To make sure I was not insane, I first created a small sample project where I only lifted the relevant code, and was able to confirm that it was set up properly.
With that out of the way, I found a better solution to this issue by creating a garbage storyboard & associated view controller.
The view controller only contained this code:
class GarbageViewController: UIViewController {
#IBAction func unwind(_ segue: UIStoryboardSegue) { }
}
This was then set as the view controller for the garbage storyboard.
I then clicked on the exit outlet in the garbage storyboard file to confirm that the unwind method defined above appeared. Once it appeared, the unwind segue I wanted suddenly became available as well.
I try to perform a segue programatically from one view to another, way after it's been loaded (server sends an order to proceed) but it won't happen because "whose view is not in view hierarchy". Any ideas on how to solve it?
P.S. I don't perform any segues from viewDidLoad() method, all of them are performed from a method which is also called from another method in this class (which reads a dictionary, sent from the server). Also I tried to perform segues like this
dispatch_async(dispatch_get_main_queue(), {
self.performSegueWithIdentifier("seg_wait_ready", sender: self)
})
and just like this (even though I know this is wrong):
performSegueWithIdentifier("seg_wait_ready", sender: self)
None of these work, I still get the same warning.
I solved this issue by changing the logic of how my application changes VCs. Now I do it directly through the delegate by doing the following (roughly):
delegate.window!.rootViewController = destinationViewController
It cost me all the system transition animations but I like to do custom ones anyway. But remember to keep it in main queue. To do it safe put it in the main queue manually like this:
dispatch_async(dispatch_get_main_queue(), {delegate.window! ... })