Xcode 11：使用 Objective-C 的安全区域代码实现不起作用

Question

我是 iOS 应用程序开发的新手，目前正在开发使用 Objective-C 编写的现有 iOS 应用程序。我遇到了一个需要以编程方式实现安全区域的要求。所以我在“viewDidLoad”方法中实现了以下代码。

if(@available(iOS 11, *)){
    UILayoutGuide * guide = self.view.safeAreaLayoutGuide;
    [self.view.leadingAnchor constraintEqualToAnchor:guide.leadingAnchor].active = YES;
    [self.view.trailingAnchor constraintEqualToAnchor:guide.trailingAnchor].active = YES;
    [self.view.topAnchor constraintEqualToAnchor:guide.topAnchor].active = YES;
    [self.view.bottomAnchor constraintEqualToAnchor:guide.bottomAnchor].active = YES;
}else{
    UILayoutGuide * margins = self.view.layoutMarginsGuide;
    [self.view.leadingAnchor constraintEqualToAnchor:margins.leadingAnchor].active = YES;
    [self.view.trailingAnchor constraintEqualToAnchor:margins.trailingAnchor].active = YES;
    [self.view.topAnchor constraintEqualToAnchor:self.topLayoutGuide.bottomAnchor].active = YES;
    [self.view.bottomAnchor constraintEqualToAnchor:self.bottomLayoutGuide.topAnchor].active = YES;
}

但是，当我尝试运行连接到 iPhone XR iOS 模拟器设备的应用程序时，上面的代码不起作用。在横向模式下的安全区域之后视图没有开始，而是从安全区域本身开始，因此文本被截断

我错过了什么吗？您能否建议需要做什么才能实施安全区域？

Answer 1

您要在视图中布局什么 UI 元素？你提到文字被切断了。您提供的代码将视图中的锚点设置为自身，不设置为 UI 元素。更新您的代码以将 UI 元素的锚点设置为视图。

UITextField *textField; // Your text UI element
UILayoutGuide * guide = self.view.safeAreaLayoutGuide;
[textField.leadingAnchor constraintEqualToAnchor:guide.leadingAnchor].active = YES;
[textField.trailingAnchor constraintEqualToAnchor:guide.trailingAnchor].active = YES;
[textField.topAnchor constraintEqualToAnchor:guide.topAnchor].active = YES;
[textField.bottomAnchor constraintEqualToAnchor:guide.bottomAnchor].active = YES;

Answer 2

我建议你使用

constraintEqualToSystemSpacingAfterAnchor: multiplier:

和

constraintEqualToSystemSpacingBelowAnchor: multiplier:

而不是

constraintEqualToAnchor:

另外我建议您尝试手动将 translatesAutoresizingMaskIntoConstraints 设置为 NO：

textField.translatesAutoresizingMaskIntoConstraints = NO;

完整代码：

UITextField *textField = [[UITextField alloc] init];

textField.translatesAutoresizingMaskIntoConstraints = NO;

[self.view addSubview:textField];

if (@available(iOS 11, *)) {
    UILayoutGuide * guide = self.view.safeAreaLayoutGuide;

    [textField.leadingAnchor constraintEqualToSystemSpacingAfterAnchor:guide.leadingAnchor
                                                            multiplier:1.0].active = YES;

    [textField.trailingAnchor constraintEqualToSystemSpacingAfterAnchor:guide.trailingAnchor
                                                             multiplier:-1.0].active = YES;

    [textField.topAnchor constraintEqualToSystemSpacingBelowAnchor:guide.topAnchor
                                                        multiplier:1.0].active = YES;

    [textField.bottomAnchor constraintEqualToSystemSpacingBelowAnchor:guide.bottomAnchor
                                                           multiplier:1.0].active = YES;
} else {
    // ...
}