Update for iOS 15

根据下面的pawello2222's answer，新的interactiveDismissDisabled(_:) API现在支持这一点.

struct ContentView: View {
    @State private var showSheet = false

    var body: some View {
        Text("Content View")
            .sheet(isPresented: $showSheet) {
                Text("Sheet View")
                    .interactiveDismissDisabled(true)
            }
    }
}

Pre-iOS-15 answer

我也想这么做，但在任何地方都找不到解决方案.劫持拖动手势的答案是可行的，但当它通过滚动视图或窗体而被取消时，答案就不起作用了.问题中的方法也不太老套，所以我进一步研究了它.

对于我的用例，我有一个表格，理想情况下，当没有内容时，可以将其删除，但当有内容时，必须通过alert 进行确认.

我对这个问题的解决方案是:

struct ModalSheetTest: View {
    @State private var showModally = false
    @State private var showSheet = false
    
    var body: some View {
        Form {
            Toggle(isOn: self.$showModally) {
                Text("Modal")
            }
            Button(action: { self.showSheet = true}) {
                Text("Show sheet")
            }
        }
        .sheet(isPresented: $showSheet) {
            Form {
                Button(action: { self.showSheet = false }) {
                    Text("Hide me")
                }
            }
            .presentation(isModal: self.showModally) {
                print("Attempted to dismiss")
            }
        }
    }
}

状态值showModally确定是否必须以模式显示.如果是这样，将其向下拖动到Disclose只会触发关闭，该关闭只会在示例中打印"Attemed to Disclose"，但可用于显示确认解除的alert .

struct ModalView<T: View>: UIViewControllerRepresentable {
    let view: T
    let isModal: Bool
    let onDismissalAttempt: (()->())?
    
    func makeUIViewController(context: Context) -> UIHostingController<T> {
        UIHostingController(rootView: view)
    }
    
    func updateUIViewController(_ uiViewController: UIHostingController<T>, context: Context) {
        context.coordinator.modalView = self
        uiViewController.rootView = view
        uiViewController.parent?.presentationController?.delegate = context.coordinator
    }
    
    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }
    
    class Coordinator: NSObject, UIAdaptivePresentationControllerDelegate {
        let modalView: ModalView
        
        init(_ modalView: ModalView) {
            self.modalView = modalView
        }
        
        func presentationControllerShouldDismiss(_ presentationController: UIPresentationController) -> Bool {
            !modalView.isModal
        }
        
        func presentationControllerDidAttemptToDismiss(_ presentationController: UIPresentationController) {
            modalView.onDismissalAttempt?()
        }
    }
}

extension View {
    func presentation(isModal: Bool, onDismissalAttempt: (()->())? = nil) -> some View {
        ModalView(view: self, isModal: isModal, onDismissalAttempt: onDismissalAttempt)
    }
}

这非常适合我的用例，希望它也能帮助你或其他人.