superview

It also center aligns the view and superview.

它还让视图的中心跟父视图的中心对齐。

´Spacer view 4´ has a bottom space constraint to superview.

间隔查看4 ´的底部空间制约上海华。

Or if you do not want to have an image that big, make sure you put constraints on width and height and just center it the superview.

或者如果您不希望有大图片，请确保您对宽度和高度设置限制将其置于超级视图中。

It may not be obvious, but the second and third layouts produce identical behaviors: They both maintain a fixed margin between the view and its superview as the superview´s width changes.

或许不是很明显，但是第二第三个布局产生一样的行为：即使父视图的尺寸发生改变，它们都让视图和父视图的边距保持不变。