如何在.interactiveDismissDisabled(true)时检测用户的sheet滑动解散尝试？

在SwiftUI里，直接设置.interactiveDismissDisabled(true)会完全拦截滑动解散的手势，导致没法检测到用户的解散尝试。可以通过以下两种方式实现你要的需求：

方法一：用UIKit代理监听解散请求 #

通过包装UIKit的代理对象，精准捕获sheet的解散请求：

import SwiftUI
import UIKit

struct SheetDismissInterceptor: UIViewControllerRepresentable {
    var hasUnsavedChanges: Bool
    var onAttemptDismiss: () -> Void
    
    func makeUIViewController(context: Context) -> UIViewController {
        let vc = UIViewController()
        vc.modalPresentationStyle = .overFullScreen
        return vc
    }
    
    func updateUIViewController(_ uiViewController: UIViewController, context: Context) {
        guard let presentationController = uiViewController.parent?.presentationController else { return }
        context.coordinator.hasUnsavedChanges = hasUnsavedChanges
        context.coordinator.onAttemptDismiss = onAttemptDismiss
        presentationController.delegate = context.coordinator
    }
    
    func makeCoordinator() -> Coordinator {
        Coordinator()
    }
    
    class Coordinator: NSObject, UIAdaptivePresentationControllerDelegate {
        var hasUnsavedChanges = false
        var onAttemptDismiss: (() -> Void)?
        
        func presentationControllerShouldDismiss(_ presentationController: UIPresentationController) -> Bool {
            if hasUnsavedChanges {
                onAttemptDismiss?()
                return false
            }
            return true
        }
    }
}

// 实际使用示例
struct ContentView: View {
    @State private var showSheet = false
    @State private var hasUnsavedChanges = false
    @State private var showConfirmAlert = false
    
    var body: some View {
        Button("打开编辑Sheet") {
            showSheet = true
        }
        .sheet(isPresented: $showSheet) {
            EditSheetView(hasUnsavedChanges: $hasUnsavedChanges)
                .background(SheetDismissInterceptor(
                    hasUnsavedChanges: hasUnsavedChanges,
                    onAttemptDismiss: {
                        showConfirmAlert = true
                    }
                ))
                .alert("确定要放弃修改并关闭吗？", isPresented: $showConfirmAlert) {
                    Button("取消", role: .cancel) {}
                    Button("放弃修改", role: .destructive) {
                        showSheet = false
                    }
                }
        }
    }
}

struct EditSheetView: View {
    @Binding var hasUnsavedChanges: Bool
    @State private var inputText = ""
    
    var body: some View {
        TextField("输入内容", text: $inputText)
            .onChange(of: inputText) { _ in
                hasUnsavedChanges = true
            }
            .padding()
    }
}

方法二：自定义滑动手势替代系统手势 #

禁用系统的滑动解散，自己添加拖动手势来模拟，触发时判断是否需要弹出确认：

struct ContentView: View {
    @State private var showSheet = false
    @State private var hasUnsavedChanges = false
    @State private var showConfirmAlert = false
    
    var body: some View {
        Button("打开编辑Sheet") {
            showSheet = true
        }
        .sheet(isPresented: $showSheet) {
            EditSheetView(hasUnsavedChanges: $hasUnsavedChanges)
                .interactiveDismissDisabled(true) // 关掉系统自带的滑动手势
                .gesture(
                    DragGesture(minimumDistance: 20, coordinateSpace: .global)
                        .onEnded { gesture in
                            // 判断是否是向下滑动的解散手势
                            if gesture.translation.height > 50 {
                                if hasUnsavedChanges {
                                    showConfirmAlert = true
                                } else {
                                    showSheet = false
                                }
                            }
                        }
                )
                .alert("确定要放弃修改并关闭吗？", isPresented: $showConfirmAlert) {
                    Button("取消", role: .cancel) {}
                    Button("放弃修改", role: .destructive) {
                        showSheet = false
                    }
                }
        }
    }
}

struct EditSheetView: View {
    @Binding var hasUnsavedChanges: Bool
    @State private var inputText = ""
    
    var body: some View {
        TextField("输入内容", text: $inputText)
            .onChange(of: inputText) { _ in
                hasUnsavedChanges = true
            }
            .padding()
    }
}

两种方法对比 #

• 方法一兼容性更强，能捕获所有触发sheet解散的操作（包括滑动、点击外部），体验更贴合系统原生
• 方法二实现更简单，但需要自己调整手势的判断逻辑，可能没法完全复刻系统手势的细节

内容的提问来源于stack exchange，提问作者Ilja