如何使基于FSCalendar的UIViewRepresentable适配UIView类型？

你当前的CalendarViewRepresentable是SwiftUI的View实现，本身并非UIKit的UIView类型。要让它能作为标准UIView使用，核心是通过UIHostingController完成SwiftUI视图到UIKit视图的桥接，以下是两种可行方案：

方案一：直接在UIKit控制器中包装使用 #

如果只是需要在某个UIViewController中快速集成，直接用UIHostingController承载你的SwiftUI日历视图即可：

// 在UIViewController的viewDidLoad或其他生命周期方法中
override func viewDidLoad() {
    super.viewDidLoad()
    
    // 创建SwiftUI日历视图
    let calendarSwiftUIView = CalendarViewRepresentable(selectedDate: .constant(Date()))
    // 用UIHostingController包装
    let hostingController = UIHostingController(rootView: calendarSwiftUIView)
    
    // 添加到当前控制器
    addChild(hostingController)
    view.addSubview(hostingController.view)
    hostingController.didMove(toParent: self)
    
    // 设置布局约束
    hostingController.view.translatesAutoresizingMaskIntoConstraints = false
    NSLayoutConstraint.activate([
        hostingController.view.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
        hostingController.view.leadingAnchor.constraint(equalTo: view.leadingAnchor),
        hostingController.view.trailingAnchor.constraint(equalTo: view.trailingAnchor),
        hostingController.view.heightAnchor.constraint(equalToConstant: 320) // 固定高度或自适应
    ])
}

方案二：封装为自定义UIView子类（高复用性） #

如果需要在多处UIKit场景中复用，建议封装成一个标准的UIView子类，内部自动完成SwiftUI视图的桥接：

1. 封装自定义UIView #

class FSCalendarWrapperView: UIView {
    // 对外暴露选中日期的属性，同步到内部SwiftUI视图
    var selectedDate: Date {
        didSet {
            hostingController?.rootView.selectedDate = .constant(selectedDate)
        }
    }
    
    private var hostingController: UIHostingController<CalendarViewRepresentable>?
    
    // 初始化方法
    init(selectedDate: Date = Date()) {
        self.selectedDate = selectedDate
        super.init(frame: .zero)
        setupHostingController()
    }
    
    required init?(coder: NSCoder) {
        self.selectedDate = Date()
        super.init(coder: coder)
        setupHostingController()
    }
    
    // 内部初始化UIHostingController
    private func setupHostingController() {
        let calendarSwiftUIView = CalendarViewRepresentable(selectedDate: .constant(selectedDate))
        let hostingController = UIHostingController(rootView: calendarSwiftUIView)
        self.hostingController = hostingController
        
        // 将hostingController的view添加到当前view
        addSubview(hostingController.view)
        hostingController.view.translatesAutoresizingMaskIntoConstraints = false
        
        // 约束铺满父视图
        NSLayoutConstraint.activate([
            hostingController.view.topAnchor.constraint(equalTo: topAnchor),
            hostingController.view.leadingAnchor.constraint(equalTo: leadingAnchor),
            hostingController.view.trailingAnchor.constraint(equalTo: trailingAnchor),
            hostingController.view.bottomAnchor.constraint(equalTo: bottomAnchor)
        ])
    }
}

2. 使用自定义UIView #

和普通UIView完全一样，直接初始化添加到视图层级：

// 在UIViewController中
let calendarView = FSCalendarWrapperView(selectedDate: Date())
view.addSubview(calendarView)
calendarView.translatesAutoresizingMaskIntoConstraints = false

NSLayoutConstraint.activate([
    calendarView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
    calendarView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 16),
    calendarView.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -16),
    calendarView.heightAnchor.constraint(equalToConstant: 320)
])

原代码的优化建议 #

你提供的CalendarViewRepresentable存在两处需要修正的问题：

1. 不要把FSCalendar作为结构体属性：结构体是值类型，每次状态变化都会重新初始化，应该在makeUIView方法内创建FSCalendar实例。
2. 错误的约束设置：context.coordinator.topAnchor是无效的，Coordinator是NSObject子类，没有布局锚点，SwiftUI会自动处理UIViewRepresentable视图的布局，无需额外添加该约束。

修正后的CalendarViewRepresentable代码：

struct CalendarViewRepresentable: UIViewRepresentable {
    @Binding var selectedDate: Date
    var calendarHeight: NSLayoutConstraint?

    func updateUIView(_ uiView: FSCalendar, context: Context) { }

    func makeUIView(context: Context) -> FSCalendar {
        let calendar = FSCalendar()
        calendar.delegate = context.coordinator
        calendar.dataSource = context.coordinator
        calendar.translatesAutoresizingMaskIntoConstraints = false
        calendar.setContentHuggingPriority(.required, for: .vertical)
        calendar.setContentHuggingPriority(.required, for: .horizontal)
        return calendar
    }

    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }

    class Coordinator: NSObject, FSCalendarDelegate, FSCalendarDataSource {
        var parent: CalendarViewRepresentable

        init(_ parent: CalendarViewRepresentable) {
            self.parent = parent
        }

        func calendar(_ calendar: FSCalendar, didSelect date: Date, at monthPosition: FSCalendarMonthPosition) {
            parent.selectedDate = date
        }

        func calendar(_ calendar: FSCalendar, boundingRectWillChange bounds: CGRect, animated: Bool) {
            parent.calendarHeight?.constant = bounds.height
            // SwiftUI视图的布局更新无需手动调用layoutIfNeeded，由SwiftUI自动处理
        }
    }
}

内容的提问来源于stack exchange，提问作者devOP1