如何在 iOS、Swift 中更改底部布局约束
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How to change bottom layout constraint in iOS, Swift
提问by Joon. P
I have scroll view as @IBOutlet
我有滚动视图@IBOutlet
@IBOutlet weak var mainScrollView: UIScrollView!
I want to change the
我想改变
"Bottom space to: Bottom Layout Guide"
constraint programmatically.
以编程方式约束。
First Item : Bottom Layout Guide.Top
Relation : Equal
Second Item: Scroll View.Bottom
Constant: 0 -> 50 // (I want to change this programmatically)
Priority: 1000
Multiplier: 1
How can I do this?
我怎样才能做到这一点？
回答by Ashish Kakkad
Take the constraint as IBOutletof NSLayoutConstraint.
以约束为IBOutlet的NSLayoutConstraint。
Set the constraint outlets and change constantvalue by :
设置约束出口并constant通过以下方式更改值：
self.sampleConstraint.constant = 20
self.view.layoutIfNeeded()
回答by Dharmesh Kheni
If you are adding constraint programatically like this:
如果您像这样以编程方式添加约束：
var constraintButton = NSLayoutConstraint (item: buttonPlay,
attribute: NSLayoutAttribute.Bottom,
relatedBy: NSLayoutRelation.Equal,
toItem: self.view,
attribute: NSLayoutAttribute.Bottom,
multiplier: 1,
constant: 0)
// Add the constraint to the view
self.view.addConstraint(constraintButton)
Then you can update it this way:
然后你可以这样更新它：
self.constraintButton.constant = 50
self.view.layoutIfNeeded()
And if you want that with animation you can do it this way:
如果你想要动画，你可以这样做：
self.view.layoutIfNeeded()
UIView.animateWithDuration(1, animations: {
self.constraintButton.constant = 50
self.view.layoutIfNeeded()
})
Hope it helps.
希望能帮助到你。
回答by Juri Noga
Create an IBOutletfor your constraint:
IBOutlet为您的约束创建一个：
@property (weak, nonatomic) IBOutlet NSLayoutConstraint *bottomContraint;
And when you need to change it call:
当您需要更改它时，请调用：
bottomContstraint.constant = //your value
view.layoutIfNeeded()
Also you can animate constraint change like that:
您也可以像这样为约束更改设置动画：
bottomContstraint.constant = //your value
UIView.animateWithDuration(0.5, animations: {
self.view.layoutIfNeeded()
})
