说我有一个UIView,
class CleverView: UIView
在自定义类中,我想这样做:
func changeWidth() {
let c = ... find my own layout constraint, for "width"
c.constant = 70 * Gameinfo.ImportanceOfEnemyFactor
}
同样地,我希望能够像这样“找到”,约束(或者我猜,所有约束,可能有多个约束)附加到四个边缘之一。
因此,要查看附加到我身上的所有约束,找到任何宽度/高度,或者确实任何与给定(例如“左”)边缘相关的约束。
有什么想法吗?
或许值得注意this question
请注意(显然)我在询问如何动态/编程地执行此操作。
(是的,你可以说“链接到约束”或“使用ID” - 质量保证的重点是如何动态找到它们并动态工作。)
如果您不熟悉约束,请注意.constraints
只是为您提供“存在”的结尾。
答案 0 :(得分:17)
实际上有两种情况:
要重复。对于两个视图之间的约束。事实上,iOS确实将它们存储在最低的共同祖先中。因此,通过搜索视图的所有祖先,总是可以找到视图的约束。
因此,我们需要检查视图本身及其所有超视图的约束。一种方法可能是:
extension UIView {
// retrieves all constraints that mention the view
func getAllConstraints() -> [NSLayoutConstraint] {
// array will contain self and all superviews
var views = [self]
// get all superviews
var view = self
while let superview = view.superview {
views.append(superview)
view = superview
}
// transform views to constraints and filter only those
// constraints that include the view itself
return views.flatMap({ $0.constraints }).filter { constraint in
return constraint.firstItem as? UIView == self ||
constraint.secondItem as? UIView == self
}
}
}
您可以在获得有关视图的所有约束后应用所有类型的过滤器,我猜这是最难的部分。一些例子:
extension UIView {
// Example 1: Get all width constraints involving this view
// We could have multiple constraints involving width, e.g.:
// - two different width constraints with the exact same value
// - this view's width equal to another view's width
// - another view's height equal to this view's width (this view mentioned 2nd)
func getWidthConstraints() -> [NSLayoutConstraint] {
return getAllConstraints().filter( {
($0.firstAttribute == .width && $0.firstItem as? UIView == self) ||
($0.secondAttribute == .width && $0.secondItem as? UIView == self)
} )
}
// Example 2: Change width constraint(s) of this view to a specific value
// Make sure that we are looking at an equality constraint (not inequality)
// and that the constraint is not against another view
func changeWidth(to value: CGFloat) {
getAllConstraints().filter( {
$0.firstAttribute == .width &&
$0.relation == .equal &&
$0.secondAttribute == .notAnAttribute
} ).forEach( {$0.constant = value })
}
// Example 3: Change leading constraints only where this view is
// mentioned first. We could also filter leadingMargin, left, or leftMargin
func changeLeading(to value: CGFloat) {
getAllConstraints().filter( {
$0.firstAttribute == .leading &&
$0.firstItem as? UIView == self
}).forEach({$0.constant = value})
}
}
//编辑:增强的示例并在评论中阐明了他们的解释
答案 1 :(得分:9)
我猜您可以使用constraints
的{{3}}属性。 class CleverView: UIView {
func printSuperViewConstriantsCount() {
var c = 0
self.superview?.constraints.forEach({ (constraint) in
guard constraint.secondItem is CleverView || constraint.firstItem is CleverView else {
return
}
c += 1
print(constraint.firstAttribute.toString())
})
print("superview constraints:\(c)")
}
func printSelfConstriantsCount() {
self.constraints.forEach { (constraint) in
return print(constraint.firstAttribute.toString())
}
print("self constraints:\(self.constraints.count)")
}
}
基本上返回一个直接分配给UIView的约束数组。它不能让你获得超级视图所包含的约束,例如前导,尾随,顶部或底部,但宽度和高度约束由View本身保持。对于superview的约束,您可以遍历superview的约束。让我们说聪明的观点有这些限制:
extension NSLayoutAttribute {
func toString() -> String {
switch self {
case .left:
return "left"
case .right:
return "right"
case .top:
return "top"
case .bottom:
return "bottom"
case .leading:
return "leading"
case .trailing:
return "trailing"
case .width:
return "width"
case .height:
return "height"
case .centerX:
return "centerX"
case .centerY:
return "centerY"
case .lastBaseline:
return "lastBaseline"
case .firstBaseline:
return "firstBaseline"
case .leftMargin:
return "leftMargin"
case .rightMargin:
return "rightMargin"
case .topMargin:
return "topMargin"
case .bottomMargin:
return "bottomMargin"
case .leadingMargin:
return "leadingMargin"
case .trailingMargin:
return "trailingMargin"
case .centerXWithinMargins:
return "centerXWithinMargins"
case .centerYWithinMargins:
return "centerYWithinMargins"
case .notAnAttribute:
return "notAnAttribute"
}
}
}
<强>输出强>:
顶
领先
尾随
超视限制:3
高度
自我约束:1
要打印约束的名称,我们可以使用此扩展名
RouterModule.forRoot(routes, {useHash: false});
答案 2 :(得分:0)
可以拯救某人打字.......
根据stakri获得赏金的答案,以下是如何获得
所以......
fileprivate extension UIView {
func widthAsPointsConstraints()->[NSLayoutConstraint] {}
func widthAsFractionOfAnotherViewConstraints()->[NSLayoutConstraint] {}
}
以下全部代码。当然,你可以用同样的方式做“身高”。
所以,像这样使用它们......
let cc = someView.widthAsFractionOfAnotherViewConstraints()
for c in cc {
c.changeToNewConstraintWith(multiplier: 0.25)
}
或
let cc = someView.widthAsPointsConstraints()
for c in cc {
c.constant = 150.0
}
另外,在底部我粘贴了一个简单的演示代码,示例输出......
这是kode。 V2 ......
fileprivate extension UIView { // experimental
func allConstraints()->[NSLayoutConstraint] {
var views = [self]
var view = self
while let superview = view.superview {
views.append(superview)
view = superview
}
return views.flatMap({ $0.constraints }).filter { constraint in
return constraint.firstItem as? UIView == self ||
constraint.secondItem as? UIView == self
}
}
func widthAsPointsConstraints()->[NSLayoutConstraint] {
return self.allConstraints()
.filter({
( $0.firstItem as? UIView == self && $0.secondItem == nil )
})
.filter({
$0.firstAttribute == .width && $0.secondAttribute == .notAnAttribute
})
}
func widthAsFractionOfAnotherViewConstraints()->[NSLayoutConstraint] {
func _bothviews(_ c: NSLayoutConstraint)->Bool {
if c.firstItem == nil { return false }
if c.secondItem == nil { return false }
if !c.firstItem!.isKind(of: UIView.self) { return false }
if !c.secondItem!.isKind(of: UIView.self) { return false }
return true
}
func _ab(_ c: NSLayoutConstraint)->Bool {
return _bothviews(c)
&& c.firstItem as? UIView == self
&& c.secondItem as? UIView != self
&& c.firstAttribute == .width
}
func _ba(_ c: NSLayoutConstraint)->Bool {
return _bothviews(c)
&& c.firstItem as? UIView != self
&& c.secondItem as? UIView == self
&& c.secondAttribute == .width
}
// note that .relation could be anything: and we don't mind that
return self.allConstraints()
.filter({ _ab($0) || _ba($0) })
}
}
extension NSLayoutConstraint {
// typical routine to "change" multiplier fraction...
@discardableResult
func changeToNewConstraintWith(multiplier:CGFloat) -> NSLayoutConstraint {
//NSLayoutConstraint.deactivate([self])
self.isActive = false
let nc = NSLayoutConstraint(
item: firstItem as Any,
attribute: firstAttribute,
relatedBy: relation,
toItem: secondItem,
attribute: secondAttribute,
multiplier: multiplier,
constant: constant)
nc.priority = priority
nc.shouldBeArchived = self.shouldBeArchived
nc.identifier = self.identifier
//NSLayoutConstraint.activate([nc])
nc.isActive = true
return nc
}
}
只是一个示例演示...
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
_teste()
delay(5) {
print("changing any 'fraction fo another view' style widths ...\n\n")
let cc = self.animeHolder.widthAsFractionOfAnotherViewConstraints()
for c in cc {
c.changeToNewConstraintWith(multiplier: 0.25)
}
self._teste()
}
delay(10) {
print("changing any 'points' style widths ...\n\n")
let cc = self.animeHolder.widthAsPointsConstraints()
for c in cc {
c.constant = 150.0
}
self._teste()
}
}
func _teste() {
print("\n---- allConstraints")
for c in animeHolder.allConstraints() {
print("\n \(c)")
}
print("\n---- widthAsPointsConstraints")
for c in animeHolder.widthAsPointsConstraints() {
print("\n \(c)\n \(c.multiplier) \(c.constant)")
}
print("\n---- widthAsFractionOfAnotherViewConstraints")
for c in animeHolder.widthAsFractionOfAnotherViewConstraints() {
print("\n \(c)\n \(c.multiplier) \(c.constant)")
}
print("\n----\n")
}