这是我的Swift版本

let loginSpinner: UIActivityIndicatorView = {
    let loginSpinner = UIActivityIndicatorView(activityIndicatorStyle: .white)
    loginSpinner.translatesAutoresizingMaskIntoConstraints = false
    loginSpinner.hidesWhenStopped = true
    return loginSpinner
}()

在viewDidLoad函数中：

loginButton.addSubview(loginSpinner)
    loginSpinner.centerXAnchor.constraint(equalTo: loginButton.centerXAnchor).isActive = true
    loginSpinner.centerYAnchor.constraint(equalTo: loginButton.centerYAnchor).isActive = true

最后在需要的地方调用loginSpinner.startAnimating()和loginSpinner.stopAnimating()函数。
注意：当开始和停止动画时，我也禁用了按钮，因此取消了禁用按钮的标题，以便微调器替换标题loginButton.setTitle("", for: .disabled) // clear the title when it is disabled to just show the spinner

UIActivityIndicatorView *myspinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
    [myspinner setCenter:button.center];
    [button addSubview:myspinner];

1.你创建一个微调器（UIActivityIndicatorView），也使其自动隐藏（setHidesWhenStopped:）
1.将其作为子视图添加到按钮（addSubview）
1.你把它放在你的按钮的中心（setCenter:）
1.按下On按钮，将Title设置为空字符串（setTitle:forControlState:）并运行微调器（startAnimating）

下面是我通常的做法，还有一些不同的行为可以利用：

let spinner = UIActivityIndicatorView(activityIndicatorStyle: .White)

spinner.frame = CGRect(x: -20.0, y: 6.0, width: 20.0, height: 20.0) // (or wherever you want it in the button)
spinner.startAnimating()
spinner.alpha = 0.0

button.addSubview(spinner)

您可以相应地更改alpha。或者使用隐藏属性、停止/开始动画等。

如果有人在寻找Swift UI代码[SWIFT 5]

import SwiftUI

struct ButtonContentView: View {
    @State private var isButtonPressed = false
    @State private var isLoading = false
    
    var body: some View {
        ZStack {
            Button(action: {
                withAnimation {
                    isButtonPressed.toggle()
                    isLoading.toggle()
                }
                DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
                    withAnimation {
                        isButtonPressed.toggle()
                        isLoading.toggle()
                    }
                }
            }) {
                withAnimation(.easeInOut) {
                    Text(isButtonPressed ? "" : "Press Me")
                        .foregroundColor(.white)
                        .frame(width: isButtonPressed ? 60 : 200, height: isButtonPressed ? 60 : 50)
                        .background(Color.blue)
                        .clipShape(isButtonPressed ? RoundedRectangle(cornerRadius: 50) : RoundedRectangle(cornerRadius: 10))
                }
                
            }
            
            if isLoading {
                CircularProgressView()
                    .opacity(isButtonPressed ? 1 : 0)
                    .scaleEffect(isButtonPressed ? 1 : 0)
            }
        }
    }
}

struct CircularProgressView: View {
    @State private var rotation = 0.0
    var body: some View {
        Circle()
            .trim(from: 0.08, to: 1.0)
            .stroke(style: StrokeStyle(lineWidth: 4, lineCap: .round, lineJoin: .round))
            .foregroundColor(.white)
            .rotationEffect(.degrees(rotation))
            .frame(width: 40, height: 40)
        
            .onAppear {
                DispatchQueue.main.async {
                    withAnimation(.linear(duration: 1)
                        .repeatForever(autoreverses: false)) {
                            rotation = 360.0
                        }
                }
            }
    }
}

struct ButtonContentView_previews: PreviewProvider {
    static var previews: some View {
        ButtonContentView()
    }
}