Question

我有一个视图需要切换两个约束。

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中它看起来很好，但它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 )>

已编辑的代码

[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，当我尝试调整大小时，警告来了

Answer 1

不要删除和添加约束。添加一个约束。保持对它的引用。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);
    }];
}

我该怎样做正确的主动/主动约束？

1 个答案: