问题描述
过去一切都很好，直到昨天我将 Xcode 更新到版本 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，但是当我对按钮应用约束时，它们会消失，无论约束是什么或多少(高度、垂直间距、尾随等...)我申请了.
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.
当我点击按钮时，它们表现正常(事件总是被发送，所以我假设它们实际上位于那里(?)).我尝试更改文本颜色、背景颜色(甚至添加新的 UIButton)，但没有成功.我看不到按钮.当我更改 Centered View 的背景颜色时，我可以在应用程序上看到此更改.最奇怪的部分是当我在 Xcode 上单击 Debug View Hierarchy 以查看发生了什么时，那里的一切看起来都很好；我可以看到所有按钮都按预期定位.
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) 上测试应用程序.
Testing the app both on iPhone 5 (iOS 9.3.5) and iPhone 6 (iOS 10).
我正在使用 Swift 2.3、iOS 10 和 Xcode 8.
I am using Swift 2.3, iOS 10 and Xcode 8.
这是 Xcode 8 上的错误吗?如何解决这个问题?
Is this a bug on Xcode 8? How to resolve this issue?
更新:
我刚刚意识到 UILabel 和 UIImageView 也会出现同样的约束问题.它们在没有约束的情况下看起来很好，但是当我添加任何约束时它们就会消失.
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
我错过了将 UIButton 类设置为我的自定义类的要点.我检查了我的自定义类，发现我在 awakeFromNib() 方法上设置了圆角半径.我在设置圆角半径之前调用了 layoutIfNeeded()，这是我的解决方案.
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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