Question

我刚刚完成了我制作的一个简单Android应用程序的SwiftUI端口（感谢这里的所有人的帮助），但是它不会在画布中预览。它内置在模拟器中，但在我的手机上还不错。

这与在.onAppear中调用我的数据库选择功能有关，因为当我注释掉这部分代码时，它可以正常工作。

import SwiftUI
import AVFoundation

struct SoundPageView: View {

    var category: String
    var pageTitle: String
    var buttonRows = [ButtonData]()
    @State var btns: [[String]] = [[]]
    @State var translation: String = "Bahasa Indonesia"
    @State var gotValues: Bool = false

    var btn1: String = "First Button"
    var btn2: String = "Second Button"
    var btn3: String = "Third Button"
    var btn4: String = "Fourth Button"
    var btn5: String = "Fifth Button"
    var btn6: String = "Sixth Button"
    var btn7: String = "Seventh Button"
    var btn8: String = "Eighth Button"
    var btn9: String = "Ninth Button"
    var btn10: String = "Tenth Button"
    var btn11: String = "Eleventh Button"
    var btn12: String = "Twelfth Button"
    var btn13: String = "Thirteenth Button"
    var btn14: String = "Fourteenth Button"
    var btn15: String = "Fifteenth Button"
    var btn16: String = "Sixteenth Button"

    var body: some View {
        VStack {
            Text("\(self.translation)")
            //    .italic()
                .frame(maxWidth: .infinity)
                .multilineTextAlignment(.center)
                .frame(height: 50)
                .padding(.horizontal, 4)
            HStack(spacing:0) {
                VStack {
                    Button(action: {
                        playSound(sound: "\(self.category)_audio1", type: "mp3")
                        self.translation = self.btns[1][1]
                    }) {
                        if(gotValues==true) {
                            Text("\(self.btns[1][0])")
                        } else {
                            Text("\(self.btn1)")
                        }
                    }
                    .buttonStyle(SoundButton())
                    Button(action: {
                        playSound(sound: "\(self.category)_audio3", type: "mp3")
                        self.translation = self.btns[3][1]
                    }) {
                        if(gotValues==true) {
                            Text("\(self.btns[3][0])")
                        } else {
                            Text("\(self.btn3)")
                        }
                    }
                    .buttonStyle(SoundButton())
                    Button(action: {
                        playSound(sound: "\(self.category)_audio5", type: "mp3")
                        self.translation = self.btns[5][1]
                    }) {
                        if(gotValues==true) {
                            Text("\(self.btns[5][0])")
                        } else {
                            Text("\(self.btn5)")
                        }
                    }
                    .buttonStyle(SoundButton())
                    Button(action: {
                        playSound(sound: "\(self.category)_audio7", type: "mp3")
                        self.translation = self.btns[7][1]
                    }) {
                        if(gotValues==true) {
                            Text("\(self.btns[7][0])")
                        } else {
                            Text("\(self.btn7)")
                        }
                    }
                    .buttonStyle(SoundButton())
                    Button(action: {
                        playSound(sound: "\(self.category)_audio9", type: "mp3")
                        self.translation = self.btns[9][1]
                    }) {                            if(gotValues==true) {
                        Text("\(self.btns[9][0])")
                    } else {
                        Text("\(self.btn9)")
                        }
                    }
                    .buttonStyle(SoundButton())
                    Button(action: {
                        playSound(sound: "\(self.category)_audio11", type: "mp3")
                        self.translation = self.btns[11][1]
                    }) {
                        if(gotValues==true) {
                            Text("\(self.btns[11][0])")
                        } else {
                            Text("\(self.btn11)")
                        }
                    }
                    .buttonStyle(SoundButton())
                    Button(action: {
                        playSound(sound: "\(self.category)_audio13", type: "mp3")
                        self.translation = self.btns[13][1]
                    }) {
                        if(gotValues==true) {
                            Text("\(self.btns[13][0])")
                        } else {
                            Text("\(self.btn13)")
                        }
                    }
                    .buttonStyle(SoundButton())
                    Button(action: {
                        playSound(sound: "\(self.category)_audio15", type: "mp3")
                        self.translation = self.btns[15][1]
                    }) {
                        if(gotValues==true) {
                            Text("\(self.btns[15][0])")
                        } else {
                            Text("\(self.btn15)")
                        }
                    }
                    .buttonStyle(SoundButton())
                }
                VStack {
                    Button(action: {
                        playSound(sound: "\(self.category)_audio2", type: "mp3")
                        self.translation = self.btns[2][1]
                    }) {
                        if(gotValues==true) {
                            Text("\(self.btns[2][0])")
                        } else {
                            Text("\(self.btn2)")
                        }
                    }
                    .buttonStyle(SoundButton())
                    Button(action: {
                        playSound(sound: "\(self.category)_audio4", type: "mp3")
                        self.translation = self.btns[4][1]
                    }) {
                        if(gotValues==true) {
                            Text("\(self.btns[4][0])")
                        } else {
                            Text("\(self.btn4)")
                        }
                    }
                    .buttonStyle(SoundButton())
                    Button(action: {
                        playSound(sound: "\(self.category)_audio6", type: "mp3")
                        self.translation = self.btns[6][1]
                    }) {
                        if(gotValues==true) {
                            Text("\(self.btns[6][0])")
                        } else {
                            Text("\(self.btn6)")
                        }
                    }
                    .buttonStyle(SoundButton())
                    Button(action: {
                        playSound(sound: "\(self.category)_audio8", type: "mp3")
                        self.translation = self.btns[8][1]
                    }) {
                        if(gotValues==true) {
                            Text("\(self.btns[8][0])")
                        } else {
                            Text("\(self.btn8)")
                        }
                    }
                    .buttonStyle(SoundButton())
                    Button(action: {
                        playSound(sound: "\(self.category)_audio10", type: "mp3")
                        self.translation = self.btns[10][1]
                    }) {
                        if(gotValues==true) {
                            Text("\(self.btns[10][0])")
                        } else {
                            Text("\(self.btn10)")
                        }
                    }
                    .buttonStyle(SoundButton())
                    Button(action: {
                        playSound(sound: "\(self.category)_audio12", type: "mp3")
                        self.translation = self.btns[12][1]
                    }) {
                        if(gotValues==true) {
                            Text("\(self.btns[12][0])")
                        } else {
                            Text("\(self.btn12)")
                        }
                    }
                    .buttonStyle(SoundButton())
                    Button(action: {
                        playSound(sound: "\(self.category)_audio14", type: "mp3")
                        self.translation = self.btns[14][1]
                    }) {
                        if(gotValues==true) {
                            Text("\(self.btns[14][0])")
                        } else {
                            Text("\(self.btn14)")
                        }
                    }
                    .buttonStyle(SoundButton())
                    Button(action: {
                        playSound(sound: "\(self.category)_audio16", type: "mp3")
                        self.translation = self.btns[16][1]
                    }) {
                        if(gotValues==true) {
                            Text("\(self.btns[16][0])")
                        } else {
                            Text("\(self.btn16)")
                        }
                    }
                    .buttonStyle(SoundButton())
                }
            }

        }
        .onAppear {
            let buttonRows = DatabaseHelper().queryDatabase(category: self.category)
            for each in buttonRows {
                self.btns.append([each.english,each.indonesian])
            }
            self.gotValues = true

        }
        .navigationBarTitle(Text(self.pageTitle), displayMode: .inline)
    }
}

struct SoundPageView_Previews: PreviewProvider {
    static var previews: some View {
        SoundPageView(category: "", pageTitle: "")
    }
}

struct SoundButton: ButtonStyle {

    func makeBody(configuration: Self.Configuration) -> some View {
        configuration.label
            .font(.custom("arial", size: 20))
            .padding(.horizontal, 4).minimumScaleFactor(0.9)
            .foregroundColor(Color.black)
            .multilineTextAlignment(.center)
            .frame(maxWidth: .infinity, maxHeight: .infinity)
            .background(configuration.isPressed ? LinearGradient(gradient: Gradient(colors: [Color("DarkestGreen"), Color("LightGreen")]), startPoint: .top, endPoint: .bottom):LinearGradient(gradient: Gradient(colors: [Color("DarkGreen"), Color("LightGreen")]), startPoint: .top, endPoint: .bottom))
            .cornerRadius(10)
            .shadow(radius: 3.0)
            .overlay(
                RoundedRectangle(cornerRadius: 10)
                    .stroke(Color.white, lineWidth:2))
            .padding(2)
            .scaleEffect(configuration.isPressed ? 0.975 : 1.0)
    }
}

这是我在画布中收到的错误消息。

理想情况下，我想在.onAppear之前调用数据库函数，但不确定将其放在何处。当我创建一个init（）时，会引发很多错误。就像我说的那样，应用程序中的所有内容都可以正常运行，我只是不希望崩溃错误成为我的应用程序被Apple拒绝的原因。对于我的学生来说，这只是一个免费的应用程序，非常简单。

SwiftUI：无法在此文件中预览-* .app可能已崩溃..但构建良好

0 个答案: