autolayout的各种坑

[UIView animateWithDuration:0.5 animations:^{
//            CGRect rect = _xibView.frame;
//            rect.origin.y = 300;
//            _xibView.frame = rect;
//            
            [_xibView mas_updateConstraints:^(MASConstraintMaker *make) {
                make.top.offset(300);
                make.width.offset(100);
                make.height.offset(100);
            }];
            [self.view layoutIfNeeded];
        } completion:^(BOOL finished) {
            
        }];