当使用- transitionFromViewController:toViewController:duration:options:animations:completion:进行子viewcontroller之后，发现子controller的view比父controller的view要长一些 暂时还不知道什么原因

• 使他们在同一位置的解决方法:transitionFromViewController完成之后，重新设置子view的位置

[self transitionFromViewController:self.currentVC toViewController:self.oneTimeVC duration:0.1 options:UIViewAnimationOptionTransitionNone animations:^{
            
        } completion:^(BOOL finished) {
            if (finished) {
                self.currentVC = self.oneTimeVC;
                
                [self.currentVC.view mas_makeConstraints:^(MASConstraintMaker *make) {
                    make.edges.equalTo(self.view);
                }];
            }
        }];