与AddConstraints相反，activateConstraints不更新帧

Question

iOS 8声明UIView的addConstraints已弃用，应使用NSLayoutConstraints + activateConstraints。所以我做了一个快速测试，但事情并没有适用于新方法。

来自viewdidload或viewdidappear：

作品（标签调整大小）：

NSDictionary *views = NSDictionaryOfVariableBindings(_labelLeft);

NSArray *constraints = [NSLayoutConstraint
                        constraintsWithVisualFormat:@"V:[_labelLeft(100)]"
                        options:0
                        metrics:nil
                        views:views];

NSArray *constraint = [NSLayoutConstraint
                       constraintsWithVisualFormat:@"H:[_labelLeft(100)]"
                       options:0
                       metrics:nil
                       views:views];
[self.view addConstraints:constraints];
[self.view addConstraints:constraint];

不起作用

NSDictionary *views = NSDictionaryOfVariableBindings(_labelLeft);

NSArray *constraints = [NSLayoutConstraint
                        constraintsWithVisualFormat:@"V:[_labelLeft(100)]"
                        options:0
                        metrics:nil
                        views:views];

NSArray *constraint = [NSLayoutConstraint
                       constraintsWithVisualFormat:@"H:[_labelLeft(100)]"
                       options:0
                       metrics:nil
                       views:views];


[NSLayoutConstraint activateConstraints:constraint];
[NSLayoutConstraint activateConstraints:constraints];

任何人都知道我做错了什么？