如何修复- safeAreaLayoutGuide‘仅在iOS 11.0或更高版本上可用

Question

在我的应用程序里我有个错误-

safeAreaLayoutGuide' is only available on iOS 11.0 or newer

在此代码中，错误出现3次。基本上在我使用safeArea的每一行中。

NSLayoutConstraint.activate([
        stackViewBottomConstrols.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor),
        stackViewBottomConstrols.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor),
        stackViewBottomConstrols.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor),
        stackViewBottomConstrols.heightAnchor.constraint(equalToConstant: 50)
        ])

我是否可以检查IOS 11是否可用，并运行这段代码，并在else语句中添加另一段代码，使用相同的代码，但不使用safeArea。该视图是否与if语句中的视图相同。如果没有，还有其他解决办法吗？

这段代码会在不具有相同IOS 11的设备上工作吗？

        if #available(iOS 11.0, *) {
        NSLayoutConstraint.activate([
            stackViewBottomConstrols.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor),
            stackViewBottomConstrols.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor),
            stackViewBottomConstrols.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor),
            stackViewBottomConstrols.heightAnchor.constraint(equalToConstant: 50)
            ])
    } else {
        NSLayoutConstraint.activate([
            stackViewBottomConstrols.bottomAnchor.constraint(equalTo: view.bottomAnchor),
            stackViewBottomConstrols.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            stackViewBottomConstrols.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            stackViewBottomConstrols.heightAnchor.constraint(equalToConstant: 50)
            ])
    }

Answer 1

safeAreaLayoutGuide只是顶底布局指南的替代品，添加了前导和尾随--当然，您的代码很好，这是在代码中创建约束以支持IOS 11和更低版本的唯一方法，但只能切换到与此无关的约束。

stackViewBottomConstrols.heightAnchor.constraint(equalToConstant: 50)

变成这样

if #available(iOS 11.0, *) {
    NSLayoutConstraint.activate([
        stackViewBottomConstrols.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor),
        stackViewBottomConstrols.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor),
        stackViewBottomConstrols.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor)
     ])
} else {
    NSLayoutConstraint.activate([
        stackViewBottomConstrols.bottomAnchor.constraint(equalTo: self.bottomLayoutGuide.topAnchor),
        stackViewBottomConstrols.leadingAnchor.constraint(equalTo: view.leadingAnchor),
        stackViewBottomConstrols.trailingAnchor.constraint(equalTo: view.trailingAnchor)
     ])
      
}

Answer 2

如果您希望尽可能保持一致性，请在预iOS-11块中，将view.bottomAnchor替换为bottomLayoutGuide.topAnchor。在iOS 11之前，仍然有topLayoutGuide和bottomLayoutGuide来帮助程序员在导航栏、选项卡栏等。否则，我觉得不错！

编辑:生成代码：

if #available(iOS 11.0, *) {
    NSLayoutConstraint.activate([
        stackViewBottomConstrols.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor),
        stackViewBottomConstrols.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor),
        stackViewBottomConstrols.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor),
        ])
} else {
    NSLayoutConstraint.activate([
        stackViewBottomConstrols.bottomAnchor.constraint(equalTo: bottomLayoutGuide.topAnchor),
        stackViewBottomConstrols.leadingAnchor.constraint(equalTo: view.leadingAnchor),
        stackViewBottomConstrols.trailingAnchor.constraint(equalTo: view.trailingAnchor),
        ])
}
// This one doesn't care which iOS version it is
stackViewBottomConstrols.heightAnchor.constraint(equalToConstant: 50)