我正在向导航栏添加子视图,但问题是我无法添加约束。我得到了以下错误:
终止应用程序,因为出现未捕获的异常“NSGenericException”,原因:“无法激活约束项;值:0.000000> and >,因为它们没有共同的祖先。该约束引用了不同视图层次结构中的项目吗?那是违法的。
使用的代码如下:
//create a slider and add it to the view
let slider = UISlider()
self.navigationController?.navigationBar.addSubview(slider)
//pin the slider 20 points from the left edge of the the superview
//from the left edge of the slider to the left edge of the superview
//superview X coord is at 0 therefore 0 + 20 = 20 position
let horizonalContraints = NSLayoutConstraint(item: slider, attribute:
.LeadingMargin, relatedBy: .Equal, toItem: view,
attribute: .LeadingMargin, multiplier: 1.0,
constant: 20)
//pin the slider 20 points from the right edge of the super view
//negative because we want to pin -20 points from the end of the superview.
//ex. if with of super view is 300, 300-20 = 280 position
let horizonal2Contraints = NSLayoutConstraint(item: slider, attribute:
.TrailingMargin, relatedBy: .Equal, toItem: view,
attribute: .TrailingMargin, multiplier: 1.0, constant: -20)
//pin 100 points from the top of the super
let pinTop = NSLayoutConstraint(item: slider, attribute: .Top, relatedBy: .Equal,
toItem: view, attribute: .Top, multiplier: 1.0, constant: 100)
//when using autolayout we an a view, MUST ALWAYS SET setTranslatesAutoresizingMaskIntoConstraints
//to false.
slider.translatesAutoresizingMaskIntoConstraints = false
slider.backgroundColor = UIColor.redColor()
//IOS 8
//activate the constrains.
//we pass an array of all the contraints
NSLayoutConstraint.activateConstraints([horizonalContraints, horizonal2Contraints,pinTop])
如果我使用以下代码行view.addSubview(slider)
而不是
,上面的代码就可以正常工作。
self.navigationController?.navigationBar.addSubview(slider)
但是想法是在导航栏上的子视图上添加约束条件。 欢迎提出任何想法。