第5回 タップで値を設定できるようにする | SwiftUIでカラーピッカーを作る

struct ContentView: View {
    @State private var tappedPoint = CGPoint()
    
    var body: some View {
        VStack {
            GeometryReader { geometry in
                Path { path in
                    path.addRect(CGRect(x: 0, y: 0, width: geometry.size.width, height: geometry.size.height))
                }
                .fill(.red)
            }
            .onTapGesture { point in
                tappedPoint = point
            }
            Text("Tapped: \(tappedPoint.x), \(tappedPoint.y)")
        }
        .padding()
    }
}

PickerGradationView(startColor: redStartColor, endColor: redEndColor)
	.frame(height: 100)
	.background {
		GeometryReader { geometry in
			Path { path in
				DispatchQueue.main.async {
					if geometry.size != redGradationViewSize {
						redGradationViewSize = geometry.size
					}
				}
			}
		}
	}
	.onTapGesture { point in
		channelValue.red = point.x / redGradationViewSize.width
	}