UIKit Picker in SwiftUI scroll moves to next value

I'm using UIKit picker in SwiftUI. To minimize the memory concerns with my picker's large number of values in my project, I decided to move UIKit picker in SwiftUI. When I quickly scroll the picker from top to bottom and vice versa, my picker occasionally leaps to the next value from the top or from bottom to the next/previous value. Steps to reproduce: Create a UIKit picker in SwiftUI Scroll the picker quickly from top to bottom and vice versa Intermittently, the selected value moves to the next value in the picker Code: Below attached sample code for reference


    @State private var isPresented = false
    @State private var selection: [Int] = [5]
    @State var visiblePicker: Bool = false

    private let data: [[String]] = [
        Array(0...10).map { "\($0)" }
    ]

    var body: some View {
        VStack(spacing: 5) {
            Button("Picker") {
                self.isPresented = true
            }
            Text("\(self.data[0][self.selection[0]])")
                .onTapGesture {
                    self.visiblePicker.toggle()
                }
        }
            PickerView(data: self.data, selections: self.$selection)
    }
}

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

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

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

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

        return picker
    }

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

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

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

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

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

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

        func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
            print("selected row = \(row)")
            self.parent.selections[component] = row
        }
    }
}
Answered by DTS Engineer in 801033022

pickerView(_:didSelectRow:inComponent:) while give you the currently selected row while pickerView(_:titleForRow:forComponent:) will gave you scrolling value. You might want to use that instead.

pickerView(_:didSelectRow:inComponent:) while give you the currently selected row while pickerView(_:titleForRow:forComponent:) will gave you scrolling value. You might want to use that instead.

UIKit Picker in SwiftUI scroll moves to next value
 
 
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