Otomatik Düzenleme kısıtlamaları constraintEqualToAnchor() kullanıldığında ayarlandıktan sonra nasıl değiştirilir?

Question

Ben constraintEqualToAnchor() kullanarak AutoLayout kısıtlamalarıyla bir görünümü ayarlamak için deneyin:

kodunun son satırında

override func viewDidLoad() { 
    super.viewDidLoad() 

    let myView = UIView() 
    myView.backgroundColor = UIColor.orangeColor() 
    myView.translatesAutoresizingMaskIntoConstraints = false 
    view.addSubview(myView) 

    myView.leftAnchor.constraintEqualToAnchor(view.leftAnchor).active = true 
    myView.trailingAnchor.constraintEqualToAnchor(view.trailingAnchor).active = true 
    myView.topAnchor.constraintEqualToAnchor(view.topAnchor).active = true 
    myView.bottomAnchor.constraintEqualToAnchor(view.bottomAnchor).active = true 

    /******************************************/ 
    /* I try to change one of the constraints */ 
    /******************************************/ 
    myView.leftAnchor.constraintEqualToAnchor(view.rightAnchor, constant: -100).active = true 
} 

, çok kısıtlı birini değiştirmek deneyin. Ben o iş düşündüm ama constraintEqualToAnchor()? kullanarak, onları belirledik sonra sonra kısıtlamayı değiştirmek için doğru yolu nedir zaman konsol günlüğüne

"<NSLayoutConstraint:0x7fb53a5180d0 H:|-(0)-[UIView:0x7fb53a5190b0](LTR) (Names: '|':UIView:0x7fb53a519240)>", 
"<NSLayoutConstraint:0x7fb53a51f660 H:[UIView:0x7fb53a519240]-(-100)-[UIView:0x7fb53a5190b0](LTR)>", 
"<NSLayoutConstraint:0x7fb53a711ee0 'UIView-Encapsulated-Layout-Width' H:[UIView:0x7fb53a519240(414)]>" 

bazı hata veriyor?

Answer 1

Yeni bir tane aktive olduğunda önceki kısıtlamayı devre dışı bırakmanız gerekir. Bunu yapmak için, ViewController bir özellik olarak kısıtların her bir başvuru depolamak ve daha sonra yeni kısıtlamayı oluşturma ve etkinleştirmeden önce false eski kısıtlaması active özelliğini ayarlayın:

Swift 2.x:

class ViewController: UIViewController { 
    var leftConstraint: NSLayoutConstraint? 
    var trailingConstraint: NSLayoutConstraint? 
    var topConstraint: NSLayoutConstraint? 
    var bottomConstraint: NSLayoutConstraint? 

    override func viewDidLoad() { 
     super.viewDidLoad() 

     let myView = UIView() 
     myView.backgroundColor = UIColor.orangeColor() 
     myView.translatesAutoresizingMaskIntoConstraints = false 
     view.addSubview(myView) 

     leftConstraint = myView.leftAnchor.constraintEqualToAnchor(view.leftAnchor) 
     leftConstraint?.active = true 

     trailingConstraint = myView.trailingAnchor.constraintEqualToAnchor(view.trailingAnchor) 
     trailingConstraint?.active = true 

     topConstraint = myView.topAnchor.constraintEqualToAnchor(view.topAnchor) 
     topConstraint?.active = true 

     bottomConstraint = myView.bottomAnchor.constraintEqualToAnchor(view.bottomAnchor) 
     bottomConstraint?.active = true 

     /******************************************/ 
     /* I try to change one of the constraints */ 
     /******************************************/ 
     leftConstraint?.active = false 
     leftConstraint = myView.leftAnchor.constraintEqualToAnchor(view.rightAnchor, constant: -100) 
     leftConstraint?.active = true 
    } 
} 

---

Güncelleme için Swift 3 sözdizimi:

class ViewController: UIViewController { 
    var leftConstraint: NSLayoutConstraint? 
    var trailingConstraint: NSLayoutConstraint? 
    var topConstraint: NSLayoutConstraint? 
    var bottomConstraint: NSLayoutConstraint? 

    override func viewDidLoad() { 
     super.viewDidLoad() 

     let myView = UIView() 
     myView.backgroundColor = UIColor.orange 
     myView.translatesAutoresizingMaskIntoConstraints = false 
     view.addSubview(myView) 

     leftConstraint = myView.leftAnchor.constraint(equalTo: view.leftAnchor) 
     leftConstraint?.isActive = true 

     trailingConstraint = myView.trailingAnchor.constraint(equalTo: view.trailingAnchor) 
     trailingConstraint?.isActive = true 

     topConstraint = myView.topAnchor.constraint(equalTo: view.topAnchor) 
     topConstraint?.isActive = true 

     bottomConstraint = myView.bottomAnchor.constraint(equalTo: view.bottomAnchor) 
     bottomConstraint?.isActive = true 

     /******************************************/ 
     /* I try to change one of the constraints */ 
     /******************************************/ 
     leftConstraint?.isActive = false 
     leftConstraint = myView.leftAnchor.constraint(equalTo: view.rightAnchor, constant: -100) 
     leftConstraint?.isActive = true 
    } 
} 

İşte

Answer 2

Aşağıda, daha sonra başvurulan bir kısıtlama c bildiren bir örnek verilmiştir. Yeni bir sabit değer belirledik ve ardından süper görünümde layout'u aradık. Eğer görünümü zorlayıcı üzerinde sona kalmamak

myView.translatesAutoresizingMaskIntoConstraints = false 

var constraints: [NSLayoutConstraint] = [ 
    myView.topAnchor.constraintEqualToAnchor(view.topAnchor), 
    myView.leftAnchor.constraintEqualToAnchor(view.leftAnchor), 
    myView.bottomAnchor.constraintEqualToAnchor(view.bottomAnchor) 
]   
let c = myView.rightAnchor.constraintEqualToAnchor(view.rightAnchor)  
constraints.append(c) 

view.addSubview(myView) 
NSLayoutConstraint.activateConstraints(constraints) 

// Some time later 
c.constant = -100 
view.layout() 

Answer 3

// method myView.topAnchor.constraintEqualToAnchor creates new one inactive anchor 
// and not returns exist with equal relationships  

// you can set identifier for any constraint in Interface Builder or code and find & update in code 
for (NSLayoutConstraint *c in [self.view constraintsAffectingLayoutForAxis:UILayoutConstraintAxisHorizontal]) 
{ 
    if (YES == [c.identifier isEqualToString:@"my.layout-constraint.id"]) 
    { 
     // Unlike the other properties, the constant can be modified 
     // after constraint creation. 
     // Setting the constant on an existing constraint performs much better 
     // than removing the constraint and adding a new one that's exactly like 
     // the old except that it has a different constant. 

     c.constant = 123; 

     // if needed 
     // [self.view setNeedsUpdateConstraints]; 

     break; 
    } 
} 

Answer 4

bir StackView değiştirerek EĞER deyimi ile örneğidir ve bir tıklandığında segmente zaman görüntüle: false `etmek .active` ben` myView.leftAnchor.constraintEqualToAnchor (view.leftAnchor) set düşündüm

if (sender as AnyObject).selectedSegmentIndex == 0{ 


     // Shrink the white view and stack view 
     heightConstraintView = containerView.heightAnchor.constraint(equalToConstant: 100) 
     heightConstraintView?.isActive = true 

     heightConstraintStackView = stackView.heightAnchor.constraint(equalToConstant: 100) 
     heightConstraintStackView?.isActive = true 
    } 

    else { 


     // Before returning back the white view and stack view DEACTIVATE teh previous constraints 
     heightConstraintView?.isActive = false 
     heightConstraintStackView?.isActive = false 

     // Returning back the white view and stack view to normal size 
     heightConstraintView = containerView.heightAnchor.constraint(equalToConstant: 200) 
     heightConstraintView?.isActive = true 

     heightConstraintStackView = stackView.heightAnchor.constraint(equalToConstant: 200) 
      heightConstraintStackView?.isActive = true 
    }