在SwiftUI中使用GeometryReader定位视图

import SwiftUI

struct ContentView: View {
    var body: some View {
        GeometryReader { geometry in
            VStack {
                Text("父视图大小：\(geometry.size.width) x \(geometry.size.height)")
                
                Rectangle()
                    .fill(Color.blue)
                    .frame(width: geometry.size.width * 0.8, height: geometry.size.height * 0.5)
                    .overlay(
                        Text("子视图")
                            .foregroundColor(.white)
                    )
            }
        }
    }
}

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