如何复制 UIKit/SwiftUI 元素背景（如 UITabBar/TabView 背景）

Question

我想复制 UITabBar（和类似的 UIKit/SwiftUI 元素）的背景（包括相同的模糊效果和细灰色边框及其适应性）并将其应用于另一个 UI 元素。 我怎样才能做到这一点？

我尝试复制它，但是当我将新视图堆叠在其他不同颜色的视图上时，行为会有所不同（并且不支持夜间模式）。

我不在乎答案是针对 UIKit 还是 SwiftUI 框架。

Answer 1

参见UIInterface 模块中的UIColor 扩展，如以下示例（那里有很多）：

 * 1. systemBackground
 *    Use this stack for views with standard table views, and designs which have a white
 *    primary background in light mode.
 */
@available(iOS 13.0, *)
open class var systemBackground: UIColor { get }


/* 2. systemGroupedBackground
 *    Use this stack for views with grouped content, such as grouped tables and
 *    platter-based designs. These are like grouped table views, but you may use these
 *    colors in places where a table view wouldn't make sense.
 */
@available(iOS 13.0, *)
open class var systemGroupedBackground: UIColor { get }


/* Fill colors for UI elements.
 * These are meant to be used over the background colors, since their alpha component is less than 1.
 *
 * systemFillColor is appropriate for filling thin and small shapes.
 * Example: The track of a slider.
 */
@available(iOS 13.0, *)
open class var systemFill: UIColor { get }