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。

youdao

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。

youdao