Hello everyone. I just start learning SwiftUI. Today's challenge I make a Temperature Conversion.

I think it work not so good.so there have two question for me.

First is when I use @FocusState with NavigationView, the Xcode's preview dont work but I can build succeful.I dont know just I have this problem? my Xcode Version is Version 13.2.1 (13C100).macOS is 12.1

Second is when I used FocusState but sometime the keyboard did not come out. I can just see "Done" button at right side on the screen without keyboard.

Here is my code, can someone help me? thx

//
//  ContentView.swift
//  Temperature Conversion
//
//  Created by zsjng on 2022/1/21.
//Celsius, Fahrenheit, or Kelvin

import SwiftUI

struct ContentView: View {

    @State private var inputNumber:Double = 0
    @State private var inputUnit:String = "°C"
    @State private var outputUnit:String = "F"
    @FocusState private var isOnFocus:Bool

    var outputNumber:Double {
        var answer = 0.0
        if inputUnit == "°C" && outputUnit == "F"{
            answer = inputNumber * 1.8 + 32.0
        }else if inputUnit == "F" && outputUnit == "°C"{
            answer = (inputNumber - 32.0) / 1.8
        }else if inputUnit == "°C" && outputUnit == "K"{
            answer = inputNumber + 273.15
        }else if inputUnit == "K" && outputUnit == "°C"{
            answer = inputNumber - 273.15
        }else if inputUnit == "F" && outputUnit == "K"{
            answer = (inputNumber + 459.67) * 5.0 / 9.0
        }else if inputUnit == "K" && outputUnit == "F"{
            answer = inputNumber * 1.8 - 459.67
        }else{
            answer = inputNumber
        }
        return answer
    }

    let Units:[String] = ["°C","F","K"]

    var body: some View {
        NavigationView{
            Form{
                Section{
                    TextField("Please input", value: $inputNumber, format:.number)
                        .keyboardType(.decimalPad)
                        .focused($isOnFocus)
                }header: {
                    Text("Please input there")
                }
                Picker("Input Unit",selection:$inputUnit){
                    ForEach(Units,id:\.self){
                        Text($0)
                    }
                }
                Picker("Output Unit",selection:$outputUnit){
                    ForEach(Units,id:\.self){
                        Text($0)
                    }
                }
                Text("\(inputNumber.formatted())" + "\(inputUnit) = " + "\(outputNumber.formatted())" + "\(outputUnit)")

            }.navigationTitle("Temperature Change")
                .toolbar{
                    ToolbarItemGroup(placement: .keyboard){
                        Spacer()
                        Button("Done"){
                            isOnFocus = false
                        }
                    }
                }
        }
    }
}
struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

@osmc94. These weird bugs are hard for new developers. Did you make the error, if so WHERE?

I pasted your entire code into a new XCode (13.2.1) project, compiled it, and ran it on my iPhone 11 with iOS 15.2.1.

It runs fine! No issues with keyboard. Navigation works nicely. Calculations are accurate.

In his videos, @twostraws has often mentioned that the Preview panel often does not work properly. Or takes its time. Or fails to draw. There are too many to note here. It may not be worth the effort to try and find a reason. Instead, keep up with the latest updates on your OS and XCode versions.

If the preview doesn't compile, try the usual: Clean Build. Test on real iPhone.

Probably not the best answer for you. Keep coding!

I've given up on using the Preivew panel. It seems so flaky and inconsistent.

Thanks a lot guys.I decide to reinstall my mac and Xcode .then I will see if it will solved.