根據設備方向快速更改約束

Question

當設備從縱向旋轉到橫向時，視圖的寬度約束會更新，但在設備從橫向旋轉到縱向時不會更新

我的代碼：

override func viewDidLoad() {
    super.viewDidLoad()
    theView.translatesAutoresizingMaskIntoConstraints = false
    theView.topAnchor.constraint(equalTo: view.topAnchor, constant: 0).isActive = true
    theView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: 0).isActive = true
    theView.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 0).isActive = true
    theView.rightAnchor.constraint(equalTo: view.rightAnchor, constant: 0).isActive = true
  }

override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {

當設備首次從縱向旋轉到橫向時，“視圖”寬度獲得視圖寬度的50％

    if UIDevice.current.orientation.isLandscape {  
       theView.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 0.50).isActive = true

從橫向旋轉到縱向不會恢復原始寬度

    } else {
       theView.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 1.00).isActive = true
    }   
}

這是一張圖片，顯示了我想要做的事情。

Answer 1

您應該在旋轉時禁用右錨點約束。

由於NSLayoutAnchor類的constraint方法始終返回新的非活動約束，因此應保留對要激活/取消激活的約束的引用。

初始化可能如下所示。

override func viewDidLoad() {
    super.viewDidLoad()
    // ...        
    widthConstraint = theView.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 0.50)
    rightConstraint = theView.rightAnchor.constraint(equalTo: view.rightAnchor, constant: 0)
    rightConstraint.isActive = true
}

有了這些參考，你就可以像這樣實現你的willRotate:方法。

override func willTransition(to newCollection: UITraitCollection, with coordinator: UIViewControllerTransitionCoordinator) {
    if UIDevice.current.orientation.isLandscape {
        rightConstraint.isActive = false
        widthConstraint.isActive = true
    }
    else {
        rightConstraint.isActive = true
        widthConstraint.isActive = false
    }
}

它看起來應該是這樣的。