Ios 为什么我的模拟得到的是一个空白的黑屏，必须以编程方式处理锚/约束？

这是我的密码。我试图将webView锚点的顶部约束到视图控制器顶部布局指南的底部，但我只是得到一个黑屏，有时控制台中出现错误：

 Unable to simultaneously satisfy constraints.
    Probably at least one of the constraints in the following list is one you don't want. 
    Try this: 
        (1) look at each constraint and try to figure out which you don't expect; 
        (2) find the code that added the unwanted constraint or constraints and fix it. 
    (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) 
(
    "<_UILayoutSupportConstraint:0x608000284d30 _UILayoutSpacer:0x6080001aa560'UIVC-topLayoutGuide'.height == 20   (active)>",
    "<_UILayoutSupportConstraint:0x6080002850a0 V:|-(0)-[_UILayoutSpacer:0x6080001aa560'UIVC-topLayoutGuide']   (active, names: '|':UIView:0x7fcfcac26cd0 )>",
    "<NSAutoresizingMaskLayoutConstraint:0x608000280fa0 h=--& v=--& WKWebView:0x7fcfcb09a400.midY == 0   (active)>",
    "<NSAutoresizingMaskLayoutConstraint:0x608000280ff0 h=--& v=--& WKWebView:0x7fcfcb09a400.height == 0   (active)>",
    "<NSLayoutConstraint:0x6080002846f0 V:[_UILayoutSpacer:0x6080001aa560'UIVC-topLayoutGuide']-(3)-[WKWebView:0x7fcfcb09a400]   (active)>",
    "<NSAutoresizingMaskLayoutConstraint:0x608000281220 h=--& v=--& 'UIView-Encapsulated-Layout-Top' UIView:0x7fcfcac26cd0.minY == 0   (active, names: '|':UIViewControllerWrapperView:0x7fcfcac08120 )>"
)

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添加导航代理：

webView.navigationDelegate = self

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然后聆听错误和导航代理，您将能够看到到底发生了什么或没有发生什么。

不知道哪个约束被自动打破-如果这不能解决问题，请添加它-我注意到几个NSAutoResizingMaskLayoutConstraint问题。你需要为每个视图设置掩码为false。对不起Rohan…添加什么？那条被注释掉的线？是的。我没看到你把那评论出来。同样，如果这不起作用，请向约束转储（它做了什么？）和您设置的其他约束添加更多内容。这是我在此控制器内设置的唯一约束，当窗口加载视图时，我仍然会看到一个空白的黑屏。希望我们不会被要求去聊天。请给我们所有的约束问题-它应该总是告诉我们它将打破什么约束-以及*所有约束-在代码和IB中，以及任何superview约束。如果没有它，就不可能调试约束问题。（除非有人忘记/注释关闭自动调整大小掩码）。

webView.navigationDelegate = self