Constraints not works correctly in a Present ViewController

Question

I've a ViewController like PopUp but the View not stay in position that I wants.

I want that this View stay on the center of screen. The below screen show the View in storyboard with the constraints seted and the result on simulator.

AlertViewController.swift

class AlertViewController : UIViewController {

    @IBOutlet weak var frameView: UIView!
    @IBOutlet weak var btCancel: UIButton!
    @IBOutlet weak var lblInfo: UILabel!

    var delegate : AlertViewControllerDelegate?

    override func viewDidLoad() {
        super.viewDidLoad()        
        self.frameView.layer.cornerRadius = 10
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
    }

    @IBAction func cancel(_ sender: Any) {
        delegate?.cancelBt()
        self.dismiss(animated: true, completion: nil)
    }
}

MainViewController.swift (show)

let alertController = self.storyboard?.instantiateViewController(withIdentifier: "AlertVC") as! AlertViewController
            alertController.providesPresentationContextTransitionStyle = true
            alertController.definesPresentationContext = true
            alertController.modalTransitionStyle = UIModalTransitionStyle.crossDissolve
            alertController.modalPresentationStyle = UIModalPresentationStyle.overCurrentContext
            alertController.delegate = self

            self.present(alertController, animated: true, completion: {})

EDIT

I tried this.

The result: (I did change the background color).

Shehata Gamal · Accepted Answer · 2018-09-25T18:16:53.897

0

Your problem is setting top , bottom , leading and trailing constraints with static values that may break when you run in device , you need to set

width,height,centerX,centerY

* good practise to make width & height proportional to screen with multiplier or content size dependent *

top label

top , centerX

activity

top to label , centerX

mid label

centerX,Y

cancel button

centerX , bottom

edited Sep 25 '18 at 18:16

answered Sep 25 '18 at 17:43

Shehata Gamal

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you duplicate centerX in the screenShoot , you need centerX and Y – Shehata Gamal Sep 25 '18 at 17:53
Yes.. Frame View.centerY and View.centerX. – Augusto Sep 25 '18 at 17:56
i see red warning may be you have an issue in it , do you position all elemnts correctly inside the frameView ?? – Shehata Gamal Sep 25 '18 at 17:59
Yes, I tried many ways, reset to suggest, set one by one... The `UIViews` inside can influence on the main frame? about constraints, of course. – Augusto Sep 25 '18 at 18:00
Do you set centerX constraint for every subview inside frameView , if no set it – Shehata Gamal Sep 25 '18 at 18:06
I did exactly that you wrote. But not works. I edited the question with the result. – Augusto Sep 26 '18 at 11:57
@Augusto Can you share a demo of this vc only in github ? – Shehata Gamal Sep 26 '18 at 11:59
I can do this without create a new project? – Augusto Sep 26 '18 at 11:59
create a new project and copy that vc from Edit->copy – Shehata Gamal Sep 26 '18 at 12:01
I did this and the layout works fine! But in my real project the bug occurs! On the new project (just copy and paste vc): https://imgur.com/a/DEgiv7v – Augusto Sep 26 '18 at 12:11
What could be causing this only in my original project?Why – Augusto Sep 26 '18 at 12:13

akseli · Answer 2 · 2018-09-25T18:45:39.733

Your issue doesn't seem to be with the constraints of the content for your alert, but with the placement/constraints of the view that you're presenting in respect with your Parent View. It would seem that you'd need to set your alert-viewer's height-width values and x,y coordinates manually in code to make them present correctly.

[EDIT] I just noticed the order that your constraints are set. Make sure you're dragging from your FrameView to your SuperView and setting the constraint in that direction. That is, FIRST ITEM: FrameView.... SECOND ITEM: SuperView... That might also be a reason for your troubles.

There's also a good discussion on some issues with auto-layout and PresentViewController here: Auto layout invalid after presenting view controller (and many situation)

Either way, I would recommend using Center Horizontally and Center Vertically as opposed to fixed-static constraint values for your 'inner view' in your AlertView. This seems to work better when scaling accross different sized displays.

Some resources you might find useful:

But, seeing as what you're presenting is a rather simple alertview, I'd recommend skipping the re-invention of the wheel and making use of some ready-made libraries that will make your life alot easier.

1.EZAlertController if all you need are text and action buttons.

2.MRProgress if all you need are loading/progress indicators.

3.NYAlertView if what you are looking for is the freedom to add your own UIView inside the alert.

These libraries take care of the 'pesky' constraint issues for you and make development a lot quicker.

[EDIT] You might want to take a look at: https://github.com/vsouza/awesome-ios#alert--action-sheet which has an excellent curated list of useful pods that really help with iOS development.

Constraints not works correctly in a Present ViewController

2 Answers2