从Xcode 12 beta版(iOS 14)开始，开发者可以使用一个名为ProgressView的新视图，它可以显示确定进度和不确定进度。

它的样式默认为CircularProgressViewStyle，这正是我们正在寻找的。

var body: some View {
    VStack {
        ProgressView()
           // and if you want to be explicit / future-proof...
           // .progressViewStyle(CircularProgressViewStyle())
    }
}

Xcode 11.倍

相当多的视图还没有在SwiftUI中表示，但很容易将它们移植到系统中。 你需要包装UIActivityIndicator并使其UIViewRepresentable。

(关于这方面的更多信息，可以在WWDC 2019的精彩演讲-集成SwiftUI中找到)

struct ActivityIndicator: UIViewRepresentable {

    @Binding var isAnimating: Bool
    let style: UIActivityIndicatorView.Style

    func makeUIView(context: UIViewRepresentableContext<ActivityIndicator>) -> UIActivityIndicatorView {
        return UIActivityIndicatorView(style: style)
    }

    func updateUIView(_ uiView: UIActivityIndicatorView, context: UIViewRepresentableContext<ActivityIndicator>) {
        isAnimating ? uiView.startAnimating() : uiView.stopAnimating()
    }
}

然后你可以使用它如下-这是一个加载叠加的例子。

注意:我更喜欢使用ZStack，而不是overlay(:_)，所以我确切地知道在我的实现中发生了什么。

struct LoadingView<Content>: View where Content: View {

    @Binding var isShowing: Bool
    var content: () -> Content

    var body: some View {
        GeometryReader { geometry in
            ZStack(alignment: .center) {

                self.content()
                    .disabled(self.isShowing)
                    .blur(radius: self.isShowing ? 3 : 0)

                VStack {
                    Text("Loading...")
                    ActivityIndicator(isAnimating: .constant(true), style: .large)
                }
                .frame(width: geometry.size.width / 2,
                       height: geometry.size.height / 5)
                .background(Color.secondary.colorInvert())
                .foregroundColor(Color.primary)
                .cornerRadius(20)
                .opacity(self.isShowing ? 1 : 0)

            }
        }
    }

}

要测试它，你可以使用下面的示例代码:

struct ContentView: View {

    var body: some View {
        LoadingView(isShowing: .constant(true)) {
            NavigationView {
                List(["1", "2", "3", "4", "5"], id: \.self) { row in
                    Text(row)
                }.navigationBarTitle(Text("A List"), displayMode: .large)
            }
        }
    }

}

结果:

除了Mojatba Hosseini的回答，

我做了一些更新，这样就可以把它放在一个快速包中:

活动指标:

import Foundation
import SwiftUI
import UIKit

public struct ActivityIndicator: UIViewRepresentable {

  public typealias UIView = UIActivityIndicatorView
  public var isAnimating: Bool = true
  public var configuration = { (indicator: UIView) in }

 public init(isAnimating: Bool, configuration: ((UIView) -> Void)? = nil) {
    self.isAnimating = isAnimating
    if let configuration = configuration {
        self.configuration = configuration
    }
 }

 public func makeUIView(context: UIViewRepresentableContext<Self>) -> UIView {
    UIView()
 }

 public func updateUIView(_ uiView: UIView, context: 
    UIViewRepresentableContext<Self>) {
     isAnimating ? uiView.startAnimating() : uiView.stopAnimating()
     configuration(uiView)
}}

扩展:

public extension View where Self == ActivityIndicator {
func configure(_ configuration: @escaping (Self.UIView) -> Void) -> Self {
    Self.init(isAnimating: self.isAnimating, configuration: configuration)
 }
}

试试这个:

import SwiftUI

struct LoadingPlaceholder: View {
    var text = "Loading..."
    init(text:String ) {
        self.text = text
    }
    var body: some View {
        VStack(content: {
            ProgressView(self.text)
        })
    }
}

更多关于SwiftUI ProgressView的信息

// Activity View

struct ActivityIndicator: UIViewRepresentable {

    let style: UIActivityIndicatorView.Style
    @Binding var animate: Bool

    private let spinner: UIActivityIndicatorView = {
        $0.hidesWhenStopped = true
        return $0
    }(UIActivityIndicatorView(style: .medium))

    func makeUIView(context: UIViewRepresentableContext<ActivityIndicator>) -> UIActivityIndicatorView {
        spinner.style = style
        return spinner
    }

    func updateUIView(_ uiView: UIActivityIndicatorView, context: UIViewRepresentableContext<ActivityIndicator>) {
        animate ? uiView.startAnimating() : uiView.stopAnimating()
    }

    func configure(_ indicator: (UIActivityIndicatorView) -> Void) -> some View {
        indicator(spinner)
        return self
    }   
}

// Usage
struct ContentView: View {

    @State var animate = false

    var body: some View {
            ActivityIndicator(style: .large, animate: $animate)
                .configure {
                    $0.color = .red
            }
            .background(Color.blue)
    }
}

在SwiftUI 2.0中，我用ProgressView制作了这个简单易用的自定义视图

这是它的样子:

代码:

import SwiftUI

struct ActivityIndicatorView: View {
    @Binding var isPresented:Bool
    var body: some View {
        if isPresented{
            ZStack{
                RoundedRectangle(cornerRadius: 15).fill(CustomColor.gray.opacity(0.1))
                ProgressView {
                    Text("Loading...")
                        .font(.title2)
                }
            }.frame(width: 120, height: 120, alignment: .center)
            .background(RoundedRectangle(cornerRadius: 25).stroke(CustomColor.gray,lineWidth: 2))
        }
    }
}

如果你想要一个swift-ui风格的解决方案，那么神奇的是:

import Foundation
import SwiftUI

struct ActivityIndicator: View {
    
    @State private var isAnimating: Bool = false
    
    var body: some View {
        GeometryReader { (geometry: GeometryProxy) in
            ForEach(0..<5) { index in
                Group {
                    Circle()
                        .frame(width: geometry.size.width / 5, height: geometry.size.height / 5)
                        .scaleEffect(calcScale(index: index))
                        .offset(y: calcYOffset(geometry))
                }.frame(width: geometry.size.width, height: geometry.size.height)
                    .rotationEffect(!self.isAnimating ? .degrees(0) : .degrees(360))
                    .animation(Animation
                                .timingCurve(0.5, 0.15 + Double(index) / 5, 0.25, 1, duration: 1.5)
                                .repeatForever(autoreverses: false))
            }
        }
        .aspectRatio(1, contentMode: .fit)
        .onAppear {
            self.isAnimating = true
        }
    }
    
    func calcScale(index: Int) -> CGFloat {
        return (!isAnimating ? 1 - CGFloat(Float(index)) / 5 : 0.2 + CGFloat(index) / 5)
    }
    
    func calcYOffset(_ geometry: GeometryProxy) -> CGFloat {
        return geometry.size.width / 10 - geometry.size.height / 2
    }
    
}

简单地使用:

ActivityIndicator()
.frame(width: 50, height: 50)

希望能有所帮助!

使用示例:

ActivityIndicator()
    .frame(width: 200, height: 200)
    .foregroundColor(.orange)