更改約束值旋轉

後，我在viewDidLoad()更改約束值旋轉

let top = isLandscape ? 30.0 : 5.0 
let bottom = isLandscape ? 60.0 : 20.0 

let topConstraint = NSLayoutConstraint(item: mySubview, attribute: .top, relatedBy: .equal, toItem: self.view, attribute: .top, multiplier: 1, constant: top) 
let bottomConstraint = NSLayoutConstraint(item: mySubview, attribute: .bottom, relatedBy: .equal, toItem: self.view, attribute: .bottom, multiplier: 1, constant: bottom) 
let leadingConstraint = NSLayoutConstraint(item: mySubview, attribute: .leading, relatedBy: .equal, toItem: self.view, attribute: .leading, multiplier: 1, constant: 50.0) 
let trailingConstraint = NSLayoutConstraint(item: mySubview, attribute: .trailing, relatedBy: .equal, toItem: self.view, attribute: .trailing, multiplier: 1, constant: 50.0) 

mySubview.translatesAutoresizingMaskIntoConstraints = false 
self.view.addSubview(mySubview) 
self.view.addConstraints([topConstraint, bottomConstraint, leadingConstraint, trailingConstraint])

我怎樣才能應用相應的constaints設備方向更改時以編程方式添加約束視圖與此代碼？我閱讀了setNeedsUpdateConstraints，但不明白如何使用它，或者它甚至可以幫助我。

來源

2017-08-22 J.Doe

我認爲這應該幫助：

override func willAnimateRotation(to toInterfaceOrientation: UIInterfaceOrientation, duration: TimeInterval) { 
    self.view.setNeedsUpdateConstraints() 
}

現在每次設備方向的變化，它會重新計算約束和必要時進行調整

來源

2017-08-22 14:41:31

但我想改變約束的價值，因爲你可以請參閱頂部和底部約束在橫向上沒有相同的值 –

現在將您的代碼寫入函數，並在方向更改時調用該函數，而不是setNeedsUpdateConstraints（）。但我認爲在這種情況下你必須刪除子視圖並重新添加它們。 –

您是否需要以編程方式添加視圖？如果您將其添加到Interface Builder中，則可以硬編碼約束，您可以從中創建IBOutlet並輕鬆修改它們 –

首先，爲約束創建類級別的變量/屬性。然後在viewDidLoad中，設置這些限制，而不是建立新的：

class MyViewController: UIViewController { 

    var topConstraint = NSLayoutConstraint() 
    var bottomConstraint = NSLayoutConstraint() 
    var leadingConstraint = NSLayoutConstraint() 
    var trailingConstraint = NSLayoutConstraint() 
    var mySubView = UIView() 

    override func viewDidLoad() { 
     super.viewDidLoad() 

     let top = isLandscape ? 30.0 : 5.0 
     let bottom = isLandscape ? 60.0 : 20.0 

     topConstraint = NSLayoutConstraint(item: mySubView, attribute: .top, relatedBy: .equal, toItem: self.view, attribute: .top, multiplier: 1, constant: top) 
     bottomConstraint = NSLayoutConstraint(item: mySubView, attribute: .bottom, relatedBy: .equal, toItem: self.view, attribute: .bottom, multiplier: 1, constant: bottom) 

     leadingConstraint = NSLayoutConstraint(item: mySubview, attribute: .leading, relatedBy: .equal, toItem: self.view, attribute: .leading, multiplier: 1, constant: 50.0) 
     trailingConstraint = NSLayoutConstraint(item: mySubview, attribute: .trailing, relatedBy: .equal, toItem: self.view, attribute: .trailing, multiplier: 1, constant: 50.0) 

     mySubview.translatesAutoresizingMaskIntoConstraints = false 
     self.view.addSubview(mySubview) 
     self.view.addConstraints([topConstraint, bottomConstraint, leadingConstraint, trailingConstraint]) 

    } 
}

然後，當你想改變的值：

let top = isLandscape ? 30.0 : 5.0 
    let bottom = isLandscape ? 60.0 : 20.0 

    topConstraint.constant = top 
    bottomConstraint.constant = bottom

來源

2017-08-22 18:05:45 DonMag

更改約束值旋轉

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