init(_:onIncrement:onDecrement:onEditingChanged:)

Discussion 議論

Use this initializer to create a stepper with a custom title that executes closures you provide when either of the stepper’s increment or decrement buttons are pressed. This version of Stepper doesn’t take a binding to a value, nor does it allow you to specify a range of acceptable values, or a step value – it simply calls the closures you provide when the control’s buttons are pressed.

The example below uses an array that holds a number of Color values, a local state variable, value, to set the control’s background color, and title label. When the user clicks or taps on the stepper’s increment or decrement buttons SwiftUI executes the relevant closure that updates value, wrapping the value to prevent overflow. SwiftUI then re-renders the view, updating the text and background color to match the current index:

struct StepperView: View {
    @State private var value = 0
    let colors: [Color] = [.orange, .red, .gray, .blue, .green,
                           .purple, .pink]


    func incrementStep() {
        value += 1
        if value >= colors.count { value = 0 }
    }


    func decrementStep() {
        value -= 1
        if value < 0 { value = colors.count - 1 }
    }


    var body: some View {
        Stepper("Value: \(value) Color: \(colors[value].description)",
                 onIncrement: incrementStep,
                 onDecrement: decrementStep)
        .padding(5)
        .background(colors[value])
    }
}