exc_breakpoint 尝试在 SwiftUI 中加载视图时

Question

我正在尝试制作条形码扫描器应用程序。我希望扫描仪在应用程序首次启动时加载，就像背景一样。然后当扫描条形码时，在顶部加载一个视图来显示产品。

在我的 ContentsView() 中加载此视图，它会启动扫描仪，然后在找到条形码后导航到 FoundItemSheet()。

import Foundation
import SwiftUI
import CodeScanner

struct barcodeScannerView: View {
    @State var isPresentingScanner = false
    @State var scannedCode: String?
    @State private var isShowingScanner = false


    var body: some View {
        NavigationView {
                if self.scannedCode != nil {
                    NavigationLink("Next page", destination: FoundItemSheet(scannedCode: scannedCode!), isActive: .constant(true)).hidden()
                }
        }
        .onAppear(perform: {
            self.isPresentingScanner = true
        })
        .sheet(isPresented: $isShowingScanner) {
            self.scannerSheet
        }
    }
    var scannerSheet : some View {
        CodeScannerView(
            codeTypes: [.qr],
            completion: { result in
                if case let .success(code) = result {
                    self.scannedCode = code
                    self.isPresentingScanner = false
                }
            }
        )
    }
}

当导航视图被按钮替换时，像这样：

    VStack(spacing: 10) {
         if self.scannedCode != nil {
            NavigationLink("Next page", destination: FoundItemSheet(scannedCode: scannedCode!), isActive: .constant(true)).hidden()
          }
          Button("Scan Code") {
              self.isPresentingScanner = true
          }
          .sheet(isPresented: $isPresentingScanner) {
              self.scannerSheet
          }
          Text("Scan a QR code to begin")

它适用于此解决方案，但我希望扫描仪在应用加载时显示，而不是在按下按钮时显示。我尝试用与按钮内容相同的 .onAppear 替换按钮，但它不起作用。

这是找到的ItemSheet()

    struct FoundItemSheet: View {
    @State private var bottomSheetShown = false
    @State var scannedCode: String?

    var body: some View {
        GeometryReader { geometry in
            BottomSheetView(
                scannedCode: self.$scannedCode,
                isOpen: self.$bottomSheetShown,
                maxHeight: geometry.size.height * 0.7
            ) {
                Color.blue
            }
        }.edgesIgnoringSafeArea(.all)
        }

    }

struct FoundItemSheet_Previews: PreviewProvider {
    static var previews: some View {
        FoundItemSheet()
    }
}

我得到 exc_breakpoint 我相信 CodeScanner 的声明位置。

我已经被困在这个问题上几个小时了，所以我会快速回复任何问题。

Answer 1

一些想法..

1) 改变修饰符的顺序

.sheet(isPresented: $isShowingScanner) {
    self.scannerSheet
}
.onAppear(perform: {
    self.isPresentingScanner = true
})

2) 延迟 sheet 激活（因为视图层次结构可能尚未为该自定义扫描仪视图准备好）

.onAppear(perform: {
    DispatchQueue.main.asyncAfter(deadline: .now() + 0.5)
       self.isPresentingScanner = true
    }
})

exc_breakpoint 尝试在 SwiftUI 中加载视图时

exc_breakpoint while trying to load view in SwiftUI

xcode

swiftui

barcode-scanner

swift5