Swift - 代碼建立NSLayoutConstraint佈局

 

NSLayoutConstraint參數說明：

/** * 建立約束 NSLayoutConstraint 參數 說明： * item 本身 * attribute * relatedBy 大於等於 小於等於 等於 ... * toItem 另一個控件 * attribute 另外一個控件的屬性 * multiplier 乘以多少 * constant : 加上多少 * NSLayoutConstraint : 某個控件的屬性值 等於 另一個控件的屬性值 乘以多少 加上多少 * 添加約束 addConstraint */

NSLayoutConstraint(item: AnyObject, attribute: NSLayoutAttribute, relatedBy: NSLayoutRelation, toItem: AnyObject?, attribute: NSLayoutAttribute, multiplier: CGFloat, constant: CGFloat)

 

建立子控件

let childView = UILabel()
childView.text = "正在連接服務器" childView.backgroundColor = UIColor.yellow //背影黃色 childView.textAlignment = .center //文本居中對齊 parentView.backgroundColor = UIColor.red//設置父元素背影紅色，方便查看效果

關閉autoresizing

// 關閉autoresizing，否則無效果 childView.translatesAutoresizingMaskIntoConstraints =false

建立約束:

//建立相對父view的左右間距各20 //左約束 let leftConstraint = NSLayoutConstraint(item: childView, attribute: NSLayoutAttribute.leading, relatedBy: NSLayoutRelation.equal, toItem: topStatusBarView, attribute:NSLayoutAttribute.leading, multiplier: 1.0, constant: 20) //右約束 let rightConstraint = NSLayoutConstraint(item: childView, attribute: NSLayoutAttribute.trailing, relatedBy: NSLayoutRelation.equal, toItem: topStatusBarView, attribute:NSLayoutAttribute.trailing, multiplier: 1.0, constant: -20) let centerConstraint = NSLayoutConstraint(item: childView, attribute: NSLayoutAttribute.centerY, relatedBy: NSLayoutRelation.equal, toItem: topStatusBarView, attribute:NSLayoutAttribute.centerY, multiplier: 1.0, constant: 0) //子控件自身高度 let heigtConstraint = NSLayoutConstraint(item: childView, attribute: NSLayoutAttribute.height, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute:NSLayoutAttribute.notAnAttribute, multiplier: 1.0, constant: 25) //子控件內部本身的屬性（高度，本身添加） childView.addConstraint(heigtConstraint) //子元素相對父親的元素，由父添加 parentView.addConstraints([leftConstraint, rightConstraint, centerConstraint])

 

例:

Swift2.3

let imgCoupon = UIImageView()
imgCoupon.frame = CGRectMake(0, 0, 16, 16) imgCoupon.loadImgByNamed("coupon") imgCoupon.tag = 12345 cell.addSubview(imgCoupon) imgCoupon.translatesAutoresizingMaskIntoConstraints = false let l = NSLayoutConstraint(item: imgCoupon, attribute: .Leading, relatedBy: .Equal, toItem: firstView, attribute: .Trailing, multiplier: 1, constant: 3) l.active = true let c = NSLayoutConstraint(item: imgCoupon, attribute: .CenterY, relatedBy: .Equal, toItem: lbName, attribute: .CenterY, multiplier: 1, constant: 0) c.active = true let h = NSLayoutConstraint(item: imgCoupon, attribute: .Height, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 1, constant: 16) h.active = true let w = NSLayoutConstraint(item: imgCoupon, attribute: .Width, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 1, constant: 16) w.active = true

Swfit2.3中使用w.active = true 而Swift3.0中是addConstraint(w)，而且attribute的值也不一樣

 

 

PS:蘋果官網API - NSLayoutConstraint