StroyBoard

动态布局

1.设置约束的active属性

self.labelCenterYNormalCons.active = NO;
self.labelCenterYKeyboardCons.active = YES;

2.第二种方法 设置priority 默认的750 250 1000

self.highlight.priority = UILayoutPriorityDefaultLow;
self.normal.priority = UILayoutPriorityDefaultHigh;