Question

我想通过动画更改uiview1（由NSLayoutConstraint视觉格式语言创建的宽度）

这是我的代码：

var constraintArray : [NSLayoutConstraint] = []

constraintArray += NSLayoutConstraint.constraints(withVisualFormat: "H:|-10-[uiview1]-10-|", options: [], metrics: nil, views: viewsDict)

constraintArray += NSLayoutConstraint.constraints(withVisualFormat: "H:|-10-[uiview2]-10-|", options: [], metrics: nil, views: viewsDict)

constraintArray += NSLayoutConstraint.constraints(withVisualFormat: "H:|-10-[uiview3]-10-|", options: [], metrics: nil, views: viewsDict)

constraintArray += NSLayoutConstraint.constraints(withVisualFormat: "V:|-100-[uiview1]-20-[uiview2]-30-[uiview3]-30-|", options: [], metrics: nil, views: viewsDict)

NSLayoutConstraint.activate(constraintArray)


func changeUIViewWidth{

    //i don't know how to change width of uiview1 by animation
    UIView.animate(withDuration: 3){
       self.view.layoutIfNeeded()
    }
}

我该怎么做？

Answer 1

在您的情况下，这将具有挑战性，因为您没有uiview1的任何显式宽度限制，可以在代码中进行更改。通过检查

中的约束，您将获得最接近的信息

constraintArray += NSLayoutConstraint.constraints(withVisualFormat: "H:|-10-[uiview1]-10-|", options: [], metrics: nil, views: viewsDict)

并调整从该行返回的每个约束（应该有两个约束）并更改其constant。

let uiview1Constraints = NSLayoutConstraint.constraints(withVisualFormat: "H:|-10-[uiview1]-10-|", options: [], metrics: nil, views: viewsDict)

...

// Make uiview1 thinner
uiview1Constraints[0].constant = 20
uiview1Constraints[1].constant = 20
UIView.animate(withDuration: 3) {
    self.view.layoutIfNeeded()
}

我建议您使用NSLayoutAnchor创建约束。它更简单，更易于阅读，也更少出错。创建constant后，您仍然可以直接对其进行操作。

swift4：如何使用NSLayoutConstraint为UIView设置动画

1 个答案: