本文介绍了如何以编程方式更改或更新NSLayoutConstraint的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我已使用代码以编程方式实现了AutoLayout：
I have implemented AutoLayout programmatically using the Code :
- (void)addConstraintWithListNavigationViewController:(UIView *)listViewNavigation y:(CGFloat)y height:(CGFloat)height
{
//WIDTH_ListTableView = 0.4
//set x = 0;
NSLayoutConstraint *constraintToAnimate1 = [NSLayoutConstraint constraintWithItem:listViewNavigation
attribute:NSLayoutAttributeLeft
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeLeft
multiplier:0.00
constant:0];
[self.view addConstraint:constraintToAnimate1];
//set y = y;
NSLayoutConstraint *constraintToAnimate2 = [NSLayoutConstraint constraintWithItem:listViewNavigation
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeBottom
multiplier:0.00
constant:y];
[self.view addConstraint:constraintToAnimate2];
//set Width = self.view.frame.size.width*0.4
NSLayoutConstraint *constraintToAnimate3 = [NSLayoutConstraint constraintWithItem:listViewNavigation
attribute:NSLayoutAttributeWidth
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeWidth
multiplier:1-WIDTH_ListTableView
constant:0.0];
[self.view addConstraint:constraintToAnimate3];
//Set height = height
NSLayoutConstraint *constraintToAnimate4 = [NSLayoutConstraint constraintWithItem:listViewNavigation
attribute:NSLayoutAttributeHeight
relatedBy:NSLayoutRelationEqual
toItem:nil
attribute:NSLayoutAttributeNotAnAttribute
multiplier:0.00
constant:height];
[self.view addConstraint:constraintToAnimate4];
}
这很完美，但每次这个ViewController都会收到通知，它将运行：
And this works perfect, but every-time this ViewController receives a Notification, it will run:
[self.view layoutIfNeeded];
但我想根据连接的布尔变量设置listViewNavigation的宽度。
But I want to set the width of listViewNavigation according a boolean variable connected.
if(connected){
listViewNavigation.view.frame.size.width = 0.4 * self.view.frame.size.width;
}
else{
listViewNavigation.view.frame.size.width = 0.6 * self.view.frame.size.width;
}
但我不知道如何更新NSLayoutConstraint：
But i do not know how can I update the NSLayoutConstraint :
NSLayoutConstraint *constraintToAnimate3 = [NSLayoutConstraint constraintWithItem:PreView
attribute:NSLayoutAttributeWidth
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeWidth
multiplier:1 - WIDTH_ListTableView
constant:0.0];
[self.view addConstraint:constraintToAnimate3];
。
推荐答案
好的，我想出来。
[self.view removeConstraint:self.constraintOld];
[self.view addConstraint:self.constraintNew];
[UIView animateWithDuration:time animations:^{
[self.view layoutIfNeeded];
}];
这篇关于如何以编程方式更改或更新NSLayoutConstraint的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！