Xcode 8 UIButton约束不显示 [英] Xcode 8 UIButtons with constraints not showing up

问题描述

一切都很好，直到昨天我更新Xcode到版本8。

Everything used to work great until yesterday I updated Xcode to version 8.

如果我不使用任何约束，我可以看到按钮，

If I don't use any constraints, I can see the buttons but when I apply constraint(s) to the buttons they disappear, no matter what or how many constraints (height, vertical spacing, trailing etc...) I apply.

当我点按的时候，按钮，他们行为正常（事件总是发送，所以我认为他们实际位于那里（？））。我试图改变文字颜色，背景颜色，（甚至添加一个新的UIButton），但结束没有运气。我看不到按钮。当我改变中心视图的背景颜色我可以看到这个变化的应用程序。最奇怪的部分是当我点击 Debug View Hierarchy 在Xcode看到发生了什么，一切看起来很好;

When I tap buttons, they act normal (events are always sent so I assume they are actually located there(?)). I tried changing text color, background color, (even adding a new UIButton) but ended with no luck. I can't see the buttons. When I change the background color of Centered View I can see this change on the app. The weirdest part is when I click Debug View Hierarchy on Xcode to see what is going on, everything looks fine there; I can see all buttons located as I expect.

在iPhone 5（iOS 9.3.5）和iPhone 6（iOS 10）上测试应用程式。

Testing the app both on iPhone 5 (iOS 9.3.5) and iPhone 6 (iOS 10).

使用Swift 2.3，iOS 10和Xcode 8。

I am using Swift 2.3, iOS 10 and Xcode 8.

这是Xcode 8上的一个错误吗？如何解决此问题？

Is this a bug on Xcode 8? How to resolve this issue?

UPDATE：

问题也发生在UILabel和UIImageView上。

I just realised same constraint problem occurs on UILabel and UIImageView too. They look fine without constraint but when I add any constraint they disappear.

推荐答案

我缺少将UIButton类设置为my自定义类。我检查了我的自定义类，并已经看到我在 awakeFromNib（）方法设置拐角半径。在我设置拐角半径之前，我调用 layoutIfNeeded（）这是我的案例中的解决方案。

I was missing the point of setting UIButton class to my custom class. I checked my custom class and have seen that I set corner radius on awakeFromNib() method. I called layoutIfNeeded() before I set corner radius which was the solution in my case.

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