Xcode。西布。为文本元素设置默认字体

Question

当我创建它们时，如何为 xib 中的 UILabel、UITextView、UITextField 等文本元素设置默认字体？现在是系统17.0。

Answer 1

无法直接在 Interface Builder 中执行此操作...但有一种方法可以通过涉及一些代码来完成此操作。

您需要递归查看子视图（因为子视图本身可以有更多的子视图）并在遇到它们时添加文本元素。

这是我的工作，在 Swift 3.0.2 中经过验证：

/// Recursively checks for UILabels, UITextFields, and UITextViews in a parent UIView and its subviews.
/// - parameter view: The UIView which may contain text elements for further, unified configuration.
/// - returns: A dictionary with UILabels, UITextFields, and UITextViews in their own arrays.
func textElementsInView(_ view: UIView) -> [String : Array<UIView>] {

    // Get the view's subviews.
    let subviews = view.subviews

    // Set up empty arrays for labels, text fields, and text views.
    var labels : [UILabel] = []
    var textFields : [UITextField] = []
    var textViews : [UITextView] = []

    // Check through the subviews in the given view.
    for subview in subviews {

        if subview.isKind(of: UILabel.classForCoder()) {

            // The subview is a label. Add it to the labels array.
            labels.append(subview as! UILabel)

        } else if subview.isKind(of: UITextField.classForCoder()) {

            // The subview is a text field. Add it to the textFields array.
            textFields.append(subview as! UITextField)

        } else if subview.isKind(of: UITextView.classForCoder()) {

            // The subview is a text view. Add it to the textViews array.
            textViews.append(subview as! UITextView)

        } else {

            // The subview isn't itself a text element...but it could have some in it!
            // Let's check it using this very function.
            let elements = textElementsInView(subview)

            // Add the labels...
            let subviewLabels = elements["labels"] as! [UILabel]
            labels.append(contentsOf: subviewLabels)

            // ...and the text fields...
            let subviewTextFields = elements["textFields"] as! [UITextField]
            textFields.append(contentsOf: subviewTextFields)

            // ...and the text views, to their respective arrays.
            let subviewTextViews = elements["textViews"] as! [UITextView]
            textViews.append(contentsOf: subviewTextViews)

        }
    }

    // Once we're done with all that, set up our elements dictionary and return it.
    let elements : [String : Array<UIView>] = ["labels" : labels, "textFields" : textFields, "textViews" : textViews]
    return elements
}

在 Swift 中普遍应用样式的示例：

// Get the text elements in the given view.
let textElements = textElementsInView(view)

// Get the labels from the textElements dictionary.
let labels = textElements["labels"] as! [UILabel]

// Apply styles to any label in the labels array, all together.
for label in labels {
    label.font = UIFont.systemFont(ofSize: 24, weight: UIFontWeightBlack)
    label.textColor = UIColor.black
}

...以及Objective-C中的方法：

- (NSDictionary*)textElementsInView: (UIView*)view {

    // First, set up mutable arrays for our text element types.
    NSMutableArray *labels = [NSMutableArray new];
    NSMutableArray *textFields = [NSMutableArray new];
    NSMutableArray *textViews = [NSMutableArray new];

    // And get an array with our subviews.
    NSArray *subviews = [view subviews];

    // Loop through the subviews in the subviews NSArray
    for(UIView* subview in subviews) {
        if ([subview classForCoder] == [UILabel class]) {
            // If the subview is a UILabel, add it to the labels array.
            [labels addObject:subview];
        } else if ([subview classForCoder] == [UITextField class]) {
            // If the subview is a UITextField, add it to the textFields array.
            [textFields addObject:subview];
        } else if ([subview classForCoder] == [UITextView class]) {
            // If the subview is a UITextView, add it to the labels array.
            [textViews addObject:subview];
        } else {
            // Try running through this function for the view if none of the above matched.
            NSDictionary *subviewTextElements = [self textElementsInView:subview];

            // Get any labels in the subview and add them to the labels array.
            NSArray *subviewLabels = [subviewTextElements objectForKey:@"labels"];
            [labels addObjectsFromArray:subviewLabels];
            // Do the same for UITextFields...
            NSArray *subviewTextFields = [subviewTextElements objectForKey:@"textFields"];
            [labels addObjectsFromArray:subviewTextFields];
            // ...and UITextViews.
            NSArray *subviewTextViews = [subviewTextElements objectForKey:@"textViews"];
            [labels addObjectsFromArray:subviewTextViews];
        }
    }

    // After all that's done, create a dictionary and return it.
    NSDictionary *textElements = @{
                                   @"labels" : labels,
                                   @"textFields" : textFields,
                                   @"textViews": textViews
    };
    return textElements;
}

这当然不是很漂亮，但这是我能想到的完成工作的唯一方法。

Answer 2

还有另一种可能的解决方案，但它比上述更“自动化”的解决方案需要更多的体力劳动。

即继承UILabel、UITextField等，并在init中为该类设置默认字体，然后在Interface Builder中选择它们各自的对象并根据需要设置子类。

鉴于这不是我对这种情况的首选解决方案，我不会详细介绍我为其他答案所做的详细说明。但是，如果您对这个解决方案感到好奇，here's a helpful link 关于子类化 UILabel 从 Swift 1 天开始。我会说从那以后事情发生了一些变化，但是您自己应该很容易弄清楚。

重要提示：这些用于通用设置样式的解决方案都不会出现在 Interface Builder 中。这些是运行时设置，因此您只需确保在构建时正确设置了这些设置。

就个人而言，我建议仅手动设置它们而不是这些解决方案中的任何一个，除非您有一些需要这些选项中的任何一个的动态情况。