ios - 约束变化不起作用

Question

我有一个 View ，其约束如下。

现在，当我按照以下方式更改为 contain 时:

     [cell addConstraint:[NSLayoutConstraint constraintWithItem:cell.view_label 
    attribute:NSLayoutAttributeLeading relatedBy:NSLayoutRelationEqual 
    toItem:cell.view_label.superview 
attribute:NSLayoutAttributeLeading multiplier:1.0 constant:60]];

            [UIView animateWithDuration:0.2 animations:^{
                [cell.view_label updateConstraints];
                [cell.view_label.superview updateConstraints];
            }];

//不工作

警告:

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. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) ( "", "" )

Will attempt to recover by breaking constraint

Break on objc_exception_throw to catch this in the debugger. The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in may also be helpful.

帮我解决这个问题

提前致谢

Answer 1

您正在那里添加一个新 约束。旧的约束仍然存在，它不能同时满足这两个条件，因此出现警告。

您需要修改现有约束的constant 属性。做到这一点的最好方法是为它做一个导出。