通过代码 新增 和 修改 NSLayoutConstraint

               

今天因为要弄一个瀑布流里面item的动态加载，

所以考虑把里面的一些空间的高度设成0从而实现“隐藏”效果

网上对这类修改是 关联 NSLayoutConstraint

然后设置对应的constant

下面是网上的答案，但是注意了，要用父类layoutIfNeeded()来重新布局

0 down vote

If you are adding constraint programatically like this: 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 viewself.view.addConstraint(constraintButton) Then you can update it this way: self.constraintButton.constant = 50self.view.layoutIfNeeded() And if you want that with animation you can do it this way: self.view.layoutIfNeeded()UIView.animateWithDuration(1, animations: {    self.constraintButton.constant = 50    self.view.layoutIfNeeded()})

0 down vote

If you are adding constraint programatically like this: 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 viewself.view.addConstraint(constraintButton) Then you can update it this way: self.constraintButton.constant = 50self.view.layoutIfNeeded() And if you want that with animation you can do it this way: self.view.layoutIfNeeded()UIView.animateWithDuration(1, animations: {    self.constraintButton.constant = 50    self.view.layoutIfNeeded()})

           

再分享一下我老师大神的人工智能教程吧。零基础！通俗易懂！风趣幽默！还带黄段子！希望你也加入到我们人工智能的队伍中来！https://blog.csdn.net/jiangjunshow