ios - UIView 阴影和 InterfaceBuilder

Question

我想使用 CALayer 向 UI(图像) View 添加投影。以下代码通常可以正常工作

previewImage.layer.shadowColor = [[UIColor blackColor] CGColor];
previewImage.layer.shadowOffset = CGSizeMake(1.0f, 1.0f);
previewImage.layer.shadowOpacity = 1.0f;
previewImage.layer.shadowRadius = 8.0f;

但是，这仅在我以编程方式创建该 View 并将其作为 subview 添加到我的主视图时才有效。当该 View 在 InterfaceBuilder 中设置并定义为 IBOutlet UIImageView 时，这不起作用。没有影子出现。那么我在这里缺少什么？

Answer 1

在你的项目中添加一个名为 UIView.swift 的文件(或者将其粘贴到任何文件中):

import UIKit

@IBDesignable extension UIView {

    /* The color of the shadow. Defaults to opaque black. Colors created
    * from patterns are currently NOT supported. Animatable. */
    @IBInspectable var shadowColor: UIColor? {
        set {
            layer.shadowColor = newValue!.CGColor
        }
        get {
            if let color = layer.shadowColor {
                return UIColor(CGColor:color)
            }
            else {
                return nil
            }
        }
    }

    /* The opacity of the shadow. Defaults to 0. Specifying a value outside the
    * [0,1] range will give undefined results. Animatable. */
    @IBInspectable var shadowOpacity: Float {
        set {
            layer.shadowOpacity = newValue
        }
        get {
            return layer.shadowOpacity
        }
    }

    /* The shadow offset. Defaults to (0, -3). Animatable. */
    @IBInspectable var shadowOffset: CGPoint {
        set {
            layer.shadowOffset = CGSize(width: newValue.x, height: newValue.y)
        }
        get {
            return CGPoint(x: layer.shadowOffset.width, y:layer.shadowOffset.height)
        }
    }

    /* The blur radius used to create the shadow. Defaults to 3. Animatable. */
    @IBInspectable var shadowRadius: CGFloat {
        set {
            layer.shadowRadius = newValue
        }
        get {
            return layer.shadowRadius
        }
    }
}

然后这将在 Interface Builder 中为实用程序面板中的每个 View 提供 > 属性检查器:

您现在可以轻松设置阴影。

注意事项:
- 阴影只会在运行时出现。
- clipsToBounds 应该是 false(默认情况下是)