Multi-Component Picker (UIPickerView) in SwiftUI

问题

I'm trying to add a three-component Picker (UIPickerView) to a SwiftUI app (in a traditional UIKit app, the data source would return 3 from the numberOfComponents method), but I can't find an example of this anywhere.

I've tried adding an HStack of three single-component Pickers, but the perspective is off from what it would be if they were all part of a single Picker.

回答1:

Updated answer in pure SwiftUI- in this example the data is of type String.

Tested on Xcode 11.1 - may not work on previous versions.

struct MultiPicker: View  {

    typealias Label = String
    typealias Entry = String

    let data: [ (Label, [Entry]) ]
    @Binding var selection: [Entry]

    var body: some View {
        GeometryReader { geometry in
            HStack {
                ForEach(0..<self.data.count) { column in
                    Picker(self.data[column].0, selection: self.$selection[column]) {
                        ForEach(0..<self.data[column].1.count) { row in
                            Text(verbatim: self.data[column].1[row])
                            .tag(self.data[column].1[row])
                        }
                    }
                    .pickerStyle(WheelPickerStyle())
                    .frame(width: geometry.size.width / CGFloat(self.data.count), height: geometry.size.height)
                    .clipped()
                }
            }
        }
    }
}

Demo:

struct ContentView: View {

    @State var data: [(String, [String])] = [
        ("One", Array(0...10).map { "\($0)" }),
        ("Two", Array(20...40).map { "\($0)" }),
        ("Three", Array(100...200).map { "\($0)" })
    ]
    @State var selection: [String] = [0, 20, 100].map { "\($0)" }

    var body: some View {
        VStack(alignment: .center) {
            Text(verbatim: "Selection: \(selection)")
            MultiPicker(data: data, selection: $selection).frame(height: 300)
        }
    }

}

Result:

回答2:

This isn't quite as elegant but it doesn't involve porting over any UIKit stuff. I know you mentioned perspective was off in your answer but perhaps the geometry here fixes that

GeometryReader { geometry in

    HStack
    {
         Picker(selection: self.$selection, label: Text(""))
         {
              ForEach(0 ..< self.data1.count)
              {
                  Text(self.data1[$0])
                     .color(Color.white)
                     .tag($0)
              }
          }
          .pickerStyle(.wheel)
          .fixedSize(horizontal: true, vertical: true)
          .frame(width: geometry.size.width / 2, height: geometry.size.height, alignment: .center)


          Picker(selection: self.$selection2, label: Text(""))
          {
               ForEach(0 ..< self.data2.count)
               {
                   Text(self.data2[$0])
                       .color(Color.white)
                       .tag($0)
               }
          }
          .pickerStyle(.wheel)
          .fixedSize(horizontal: true, vertical: true)
          .frame(width: geometry.size.width / 2, height: geometry.size.height, alignment: .center)

    }
}

Using the geometry and fixing the size like this shows the two pickers neatly taking up half the width of the screen in each half. Now you just need to handle selection from two different state variables instead of one but I prefer this way as it keeps everything in swift UI

回答3:

Here's an adaptation of the solutions above, using the UIKit picker:

import SwiftUI

struct PickerView: UIViewRepresentable {
    var data: [[String]]
    @Binding var selections: [Int]

    //makeCoordinator()
    func makeCoordinator() -> PickerView.Coordinator {
        Coordinator(self)
    }

    //makeUIView(context:)
    func makeUIView(context: UIViewRepresentableContext<PickerView>) -> UIPickerView {
        let picker = UIPickerView(frame: .zero)

        picker.dataSource = context.coordinator
        picker.delegate = context.coordinator

        return picker
    }

    //updateUIView(_:context:)
    func updateUIView(_ view: UIPickerView, context: UIViewRepresentableContext<PickerView>) {
        for i in 0...(self.selections.count - 1) {
            view.selectRow(self.selections[i], inComponent: i, animated: false)
        }
    }

    class Coordinator: NSObject, UIPickerViewDataSource, UIPickerViewDelegate {
        var parent: PickerView

        //init(_:)
        init(_ pickerView: PickerView) {
            self.parent = pickerView
        }

        //numberOfComponents(in:)
        func numberOfComponents(in pickerView: UIPickerView) -> Int {
            return self.parent.data.count
        }

        //pickerView(_:numberOfRowsInComponent:)
        func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
            return self.parent.data[component].count
        }

        //pickerView(_:titleForRow:forComponent:)
        func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
            return self.parent.data[component][row]
        }

        //pickerView(_:didSelectRow:inComponent:)
        func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
            self.parent.selections[component] = row
        }
    }
}

import SwiftUI

struct ContentView: View {
    private let data: [[String]] = [
        Array(0...10).map { "\($0)" },
        Array(20...40).map { "\($0)" },
        Array(100...200).map { "\($0)" }
    ]

    @State private var selections: [Int] = [5, 10, 50]

    var body: some View {
        VStack {
            PickerView(data: self.data, selections: self.$selections)

            Text("\(self.data[0][self.selections[0]]) \(self.data[1][self.selections[1]]) \(self.data[2][self.selections[2]])")
        } //VStack
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

来源：https://stackoverflow.com/questions/56567539/multi-component-picker-uipickerview-in-swiftui