我在一個超級視圖中創建了兩個視圖，然后在視圖之間添加了約束：_indicatorConstrainWidth = [NSLayoutConstraint constraintWithItem:self.view1 attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:self.view2 attribute:NSLayoutAttributeWidth multiplier:1.0f constant:0.0f];[_indicatorConstrainWidth setPriority:UILayoutPriorityDefaultLow];_indicatorConstrainHeight = [NSLayoutConstraint constraintWithItem:self.view1 attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:self.view2 attribute:NSLayoutAttributeHeight multiplier:1.0f constant:0.0f];[_indicatorConstrainHeight setPriority:UILayoutPriorityDefaultLow];[self addConstraint:_indicatorConstrainWidth];[self addConstraint:_indicatorConstrainHeight];現在，我想用動畫更改乘子屬性，但是我不知道如何更改乘子屬性。（我在頭文件NSLayoutConstraint.h的私有屬性中找到了_coefficient，但它是私有的。）如何更改多重屬性？我的解決方法是刪除舊的約束，并為添加新的約束multipler。
3 回答
忽然笑
TA貢獻1806條經驗 獲得超5個贊
這是Swift中的NSLayoutConstraint擴展，可以輕松設置新的乘數：
import UIKit
extension NSLayoutConstraint {
func setMultiplier(multiplier:CGFloat) -> NSLayoutConstraint {
NSLayoutConstraint.deactivateConstraints([self])
let newConstraint = NSLayoutConstraint(
item: firstItem,
attribute: firstAttribute,
relatedBy: relation,
toItem: secondItem,
attribute: secondAttribute,
multiplier: multiplier,
constant: constant)
newConstraint.priority = priority
newConstraint.shouldBeArchived = shouldBeArchived
newConstraint.identifier = identifier
NSLayoutConstraint.activateConstraints([newConstraint])
return newConstraint
}
}
在Swift 3.0中
import UIKit
extension NSLayoutConstraint {
/**
Change multiplier constraint
- parameter multiplier: CGFloat
- returns: NSLayoutConstraint
*/
func setMultiplier(multiplier:CGFloat) -> NSLayoutConstraint {
NSLayoutConstraint.deactivate([self])
let newConstraint = NSLayoutConstraint(
item: firstItem,
attribute: firstAttribute,
relatedBy: relation,
toItem: secondItem,
attribute: secondAttribute,
multiplier: multiplier,
constant: constant)
newConstraint.priority = priority
newConstraint.shouldBeArchived = self.shouldBeArchived
newConstraint.identifier = self.identifier
NSLayoutConstraint.activate([newConstraint])
return newConstraint
}
}
演示用法：
@IBOutlet weak var myDemoConstraint:NSLayoutConstraint!
override func viewDidLoad() {
let newMultiplier:CGFloat = 0.80
myDemoConstraint = myDemoConstraint.setMultiplier(newMultiplier)
//If later in view lifecycle, you may need to call view.layoutIfNeeded()
}
PIPIONE
TA貢獻1829條經驗 獲得超9個贊
我用來更改現有布局約束的乘數的輔助函數。它創建并激活了一個新的約束，并停用了舊的約束。
struct MyConstraint {
static func changeMultiplier(_ constraint: NSLayoutConstraint, multiplier: CGFloat) -> NSLayoutConstraint {
let newConstraint = NSLayoutConstraint(
item: constraint.firstItem,
attribute: constraint.firstAttribute,
relatedBy: constraint.relation,
toItem: constraint.secondItem,
attribute: constraint.secondAttribute,
multiplier: multiplier,
constant: constraint.constant)
newConstraint.priority = constraint.priority
NSLayoutConstraint.deactivate([constraint])
NSLayoutConstraint.activate([newConstraint])
return newConstraint
}
}
用法，將乘數更改為1.2：
constraint = MyConstraint.changeMultiplier(constraint, multiplier: 1.2)
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