我怎样才能正确地进行非主动/主动约束？

Posted 2023-03-11

【中文标题】我怎样才能正确地进行非主动/主动约束？

【英文标题】：How can i do properly deactive/active constraint?

【发布时间】：2018-06-11 10:19:09

【问题描述】：

我有一个视图，我需要切换哪两个约束。

我添加了以下约束

chatHalfLeadingConstraint = [NSLayoutConstraint
                                   constraintWithItem:chatHistoryChildViewController.view
                                   attribute:NSLayoutAttributeLeading
                                   relatedBy:NSLayoutRelationEqual
                                   toItem:self.view
                                   attribute:NSLayoutAttributeLeading
                                   multiplier:1.0
                                   constant:360];

chatFullLeadingConstraint = [NSLayoutConstraint
                               constraintWithItem:chatHistoryChildViewController.view
                               attribute:NSLayoutAttributeLeading
                               relatedBy:NSLayoutRelationEqual
                               toItem:self.view
                               attribute:NSLayoutAttributeLeading
                               multiplier:1.0f
                               constant:0.f];

NSLayoutConstraint *traling = [NSLayoutConstraint
                               constraintWithItem:chatHistoryChildViewController.view
                               attribute:NSLayoutAttributeTrailing
                               relatedBy:NSLayoutRelationEqual
                               toItem:self.view
                               attribute:NSLayoutAttributeTrailing
                               multiplier:1.0f
                               constant:0.f];

NSArray *chatvertConstraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|[childView]|"
                                                                       options:0
                                                                       metrics:nil
                                                                         views:@@"childView" : chatHistoryChildViewController.view];

chatFullLeadingConstraint.active = NO;
[self.view addConstraint:chatHalfLeadingConstraint];
[self.view addConstraint:chatFullLeadingConstraint];
[self.view addConstraint:traling];
[self.view addConstraints:chatvertConstraints];
[NSLayoutConstraint deactivateConstraints:@[chatFullLeadingConstraint]];

我需要停用 chatFullLeadingConstraint。在 UI 中看起来不错，但在控制台中显示以下错误。

Unable to simultaneously satisfy constraints.
    Probably at least one of the constraints in the following list is one you don't want. 
    Try this: 
        (1) look at each constraint and try to figure out which you don't expect; 
        (2) find the code that added the unwanted constraint or constraints and fix it. 
(
    "<NSLayoutConstraint:0x145f7c00 H:|-(360)-[UILayoutContainerView:0x145b8e50]   (active, names: '|':UIView:0x1458a850 )>",
    "<NSLayoutConstraint:0x145f7c50 H:|-(0)-[UILayoutContainerView:0x145b8e50]   (active, names: '|':UIView:0x1458a850 )>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x145f7c00 H:|-(360)-[UILayoutContainerView:0x145b8e50]   (active, names: '|':UIView:0x1458a850 )>

编辑的代码

[self.view addConstraint:chatHalfLeadingConstraint];
    //[self.view addConstraint:chatFullLeadingConstraint];
    [self.view addConstraint:traling];
    [self.view addConstraints:chatvertConstraints];
  //  chatFullLeadingConstraint.active = NO;
  //  [NSLayoutConstraint deactivateConstraints:@[chatFullLeadingConstraint]];


-(void)resizeRightPanelwithBlock:(OnResize)block;


[UIView animateWithDuration:0.2 delay:0 options:0 animations:^
    if (isFullScreen == false) 
        isFullScreen = true;
        [self.view removeConstraint:chatHalfLeadingConstraint];
        [self.view addConstraint:chatFullLeadingConstraint];
    else
        isFullScreen = false;
        [self.view addConstraint:chatHalfLeadingConstraint];
        [self.view removeConstraint:chatFullLeadingConstraint];
    
    [self.view layoutIfNeeded];
 completion:^(BOOL finished) 
    block(finished);
];  

现在当我尝试调整它的大小时，警告来了

【问题讨论】：

我认为你需要在添加后而不是在添加 deactivateConstraints 和 .active = NO 之前添加非活动约束，两者都是相同的

不，这不是问题

您可以在约束中添加标识符。稍后您可以通过过滤标识符上​​的约束来获得此约束，然后切换此约束的活动状态。

在 swift chatHalfLeadingConstraint.priority = UILayoutPriority.defaultLow 中让你的 chatHalfLeadingConstraint 优先级低

警告显示您同时激活了chatHalfLeadingConstraint 和chatFullLeadingConstraint，并且它们之间存在冲突。在任何给定时间，您应该只有其中一个处于活动状态。只有一个约束并根据需要更改constant 会更简单；您甚至可以为这种变化制作动画以获得良好的过渡效果。

【参考方案1】：

不要删除和添加约束。添加单个约束。保留对它的引用。根据需要将其常量属性更改为 0 或 360。

chatLeadingConstraint = [NSLayoutConstraint
                               constraintWithItem:chatHistoryChildViewController.view
                               attribute:NSLayoutAttributeLeading
                               relatedBy:NSLayoutRelationEqual
                               toItem:self.view
                               attribute:NSLayoutAttributeLeading
                               multiplier:1.0
                               constant:360];

NSLayoutConstraint *trailing = [NSLayoutConstraint
                           constraintWithItem:chatHistoryChildViewController.view
                           attribute:NSLayoutAttributeTrailing
                           relatedBy:NSLayoutRelationEqual
                           toItem:self.view
                           attribute:NSLayoutAttributeTrailing
                           multiplier:1.0f
                           constant:0.f];

NSArray *chatvertConstraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|[childView]|"
                                                                   options:0
                                                                   metrics:nil
                                                                     views:@@"childView" : chatHistoryChildViewController.view];

[self.view addConstraint:chatLeadingConstraint];
[self.view addConstraint:trailing];
[self.view addConstraints:chatvertConstraints];


-(void)resizeRightPanelToFull:(Bool)full completion:(OnResize)block;

    chatLeadingConstraint.constant = full ? 0:360

    [UIView animateWithDuration:0.2 delay:0 options:[UIViewAnimationOptions.CurveEaseInOut] animations:^
        [self.view layoutIfNeeded];
     completion:^(BOOL finished) 
        block(finished);
    ];

【讨论】：

另外，查看NSLayoutAnchor - 这是一种比直接使用NSLayoutConstraint 更好的创建约束的方法

这仍然是问题我在第一次执行此行时收到警告消息 chatLeadingConstraint.constant = full ？ 0:360 之后一切正常

警告中的冲突约束是什么？

(1) 查看每个约束并尝试找出您不期望的； (2) 找到添加了一个或多个不需要的约束的代码并修复它。 ( "<0x14ed0e20 h:><0x14dea580 h: :0x14eca060 names:><0x14ed0e20 h: names:>