iOS：为什么我的视图需要x值约束？

Question

I have two views on an iPad in landscape.

One, let's call him Fred, is a 100 pixel height rectangle that shares the same width as the superview. Fred goes directly under the navigation bar.

Two, let's call her Elize, is a square inside of Fred, sharing height. Elize belongs almost all the way to the right of Fred, barring 8 pixels.

Here Fred is green and Elize Pink/Purple.

These are the constraints I have applied to Elize:

Fred.Trailing = Elize.Trailing, with constant 8, priority 1000, and multiplier 1
Elize.Top = Fred.Top, with constant 0, priority 1000, and multiplier 1
Elize.Height = Fred.Height, with constant 0, priority 1000, and multiplier 1

Even with these constraints, Xcode gives me a red warning sign in my Document Outline, saying that Elize needs constraints for the x position. When I allow Xcode to choose this constraint for me, it chooses:

Elize.Leading = Fred.Leading, with constant 684, priority 1000, multiplier 1

This isn't good enough, because when I look at my Main Storyboard preview, Elize moves too much to the left, and is no longer in the right corner of Fred.

How can I fix this?

Answer 1

解决此问题的一种方法是向Elize添加宽度约束。

Answer 2

我的解决方案：给Elize一个Elize.Width = Elize.Width, with constant (size of Elize; it is not polite to write this information), priority 1000, multiplier 1的约束Elize.Width = Elize.Width, with constant (size of Elize; it is not polite to write this information), priority 1000, multiplier 1