SwiftUI 是 Apple 在 2019 年推出的革命性 UI 框架，采用声明式语法构建 Apple 全平台应用。下面我将全面介绍 SwiftUI 的核心概念并提供实用示例。

一、SwiftUI 核心优势

特点	说明
声明式语法	描述 UI 应该是什么样子，而不是如何一步步创建
实时预览	Xcode 中实时查看 UI 变化，无需编译运行
跨平台支持	iOS, macOS, watchOS, tvOS 统一框架
状态驱动	自动响应数据变化更新 UI
组合式组件	通过简单组件组合构建复杂界面
动画简单化	内置丰富的动画效果，一行代码实现

二、基础组件与布局

2.1、基本视图组件

import SwiftUIstruct BasicComponentsView: View {var body: some View {VStack(spacing: 20) {// 文本Text("Hello SwiftUI!").font(.largeTitle).foregroundStyle(.blue)// 按钮Button("点击我") {print("按钮被点击!")}.buttonStyle(.borderedProminent).tint(.purple)// 图片Image(systemName: "heart.fill").resizable().frame(width: 60, height: 60).foregroundStyle(.red)// 文本输入框TextField("请输入内容", text: .constant("")).textFieldStyle(.roundedBorder).padding()}.padding()}
}

2.2、布局系统

struct LayoutSystemView: View {var body: some View {HStack(spacing: 20) {// 垂直布局VStack {RoundedRectangle(cornerRadius: 15).fill(.red).frame(width: 80, height: 120)Text("VStack")}// 水平布局HStack {RoundedRectangle(cornerRadius: 15).fill(.green).frame(width: 120, height: 80)Text("HStack")}// 层叠布局ZStack {RoundedRectangle(cornerRadius: 15).fill(.blue).frame(width: 100, height: 100)Text("ZStack").foregroundStyle(.white)}}.padding()}
}

2.3、列表与导航

struct ListItem: Identifiable {let id = UUID()let name: Stringlet icon: String
}struct ListNavigationView: View {let items = [ListItem(name: "设置", icon: "gear"),ListItem(name: "收藏", icon: "star.fill"),ListItem(name: "历史记录", icon: "clock.fill"),ListItem(name: "帮助", icon: "questionmark.circle")]var body: some View {NavigationStack {List(items) { item inNavigationLink {// 详情视图VStack {Image(systemName: item.icon).resizable().scaledToFit().frame(width: 100, height: 100).foregroundStyle(.blue)Text(item.name).font(.title)}.navigationTitle(item.name)} label: {HStack {Image(systemName: item.icon).foregroundStyle(.orange)Text(item.name)}}}.navigationTitle("功能列表").toolbar {ToolbarItem(placement: .topBarTrailing) {Button(action: {}) {Image(systemName: "plus")}}}}}
}

三、状态管理与数据流

3.1、状态管理基础

struct StateManagementView: View {// 简单状态@State private var counter = 0@State private var isToggled = falsevar body: some View {VStack(spacing: 30) {// 计数器Text("计数: \(counter)").font(.title)HStack(spacing: 20) {Button("减少") { counter -= 1 }.buttonStyle(.bordered)Button("增加") { counter += 1 }.buttonStyle(.borderedProminent)}// 开关Toggle("开关状态", isOn: $isToggled).padding().background(isToggled ? .green.opacity(0.2) : .gray.opacity(0.1)).cornerRadius(10)// 根据状态显示不同内容if isToggled {Text("开关已开启!").foregroundStyle(.green).transition(.opacity)}}.padding().animation(.easeInOut, value: isToggled)}
}

3.2、数据绑定与共享

// 可观察对象
class UserSettings: ObservableObject {@Published var username = "用户"@Published var isDarkMode = false
}struct DataBindingView: View {@StateObject private var settings = UserSettings()@State private var newUsername = ""var body: some View {VStack(spacing: 30) {// 显示共享数据Text("欢迎, \(settings.username)!").font(.title)// 修改共享数据HStack {TextField("新用户名", text: $newUsername).textFieldStyle(.roundedBorder)Button("更新") {settings.username = newUsernamenewUsername = ""}.disabled(newUsername.isEmpty)}// 绑定到共享属性Toggle("深色模式", isOn: $settings.isDarkMode).padding().background(settings.isDarkMode ? .black.opacity(0.3) : .white).cornerRadius(10)// 子视图共享数据SettingsPreview(settings: settings)}.padding().environmentObject(settings)}
}// 子视图
struct SettingsPreview: View {@ObservedObject var settings: UserSettingsvar body: some View {VStack {Text("预览").font(.headline)Text("用户名: \(settings.username)")Text("模式: \(settings.isDarkMode ? "深色" : "浅色")")}.padding().background(Color.gray.opacity(0.1)).cornerRadius(10)}
}

四、高级功能与技巧

4.1、动画效果

struct AnimationsView: View {@State private var isAnimating = false@State private var rotation: Double = 0var body: some View {VStack(spacing: 50) {// 简单动画RoundedRectangle(cornerRadius: isAnimating ? 50 : 10).fill(isAnimating ? .orange : .blue).frame(width: isAnimating ? 200 : 100,height: isAnimating ? 200 : 100).rotationEffect(.degrees(rotation)).animation(.spring(response: 0.5, dampingFraction: 0.3), value: isAnimating)// 显式动画Button("旋转") {withAnimation(.easeInOut(duration: 1)) {rotation += 360}}// 切换动画状态Button(isAnimating ? "重置" : "动画开始") {isAnimating.toggle()}.buttonStyle(.borderedProminent)}}
}

4.2、绘图与自定义形状

struct DrawingView: View {var body: some View {VStack {// 基本形状HStack(spacing: 20) {Circle().fill(LinearGradient(gradient: Gradient(colors: [.blue, .purple]),startPoint: .top,endPoint: .bottom)).frame(width: 80, height: 80)Capsule().fill(AngularGradient(gradient: Gradient(colors: [.red, .yellow, .green, .blue, .purple, .red]),center: .center)).frame(width: 60, height: 100)}// 自定义路径Path { path inpath.move(to: CGPoint(x: 50, y: 0))path.addLine(to: CGPoint(x: 100, y: 50))path.addLine(to: CGPoint(x: 50, y: 100))path.addLine(to: CGPoint(x: 0, y: 50))path.closeSubpath()}.fill(LinearGradient(gradient: Gradient(colors: [.green, .mint]),startPoint: .topLeading,endPoint: .bottomTrailing)).frame(width: 100, height: 100).padding()// 自定义形状StarShape(points: 5, innerRatio: 0.45).fill(RadialGradient(gradient: Gradient(colors: [.yellow, .orange]),center: .center,startRadius: 0,endRadius: 50)).frame(width: 150, height: 150)}}
}// 自定义星形形状
struct StarShape: Shape {let points: Intlet innerRatio: CGFloatfunc path(in rect: CGRect) -> Path {Path { path inlet center = CGPoint(x: rect.width / 2, y: rect.height / 2)let outerRadius = min(rect.width, rect.height) / 2let innerRadius = outerRadius * innerRatiolet anglePerPoint = .pi * 2 / CGFloat(points)let offset = -CGFloat.pi / 2for i in 0..<points * 2 {let angle = offset + anglePerPoint * CGFloat(i)let radius = i.isMultiple(of: 2) ? outerRadius : innerRadiuslet point = CGPoint(x: center.x + radius * cos(angle),y: center.y + radius * sin(angle))if i == 0 {path.move(to: point)} else {path.addLine(to: point)}}path.closeSubpath()}}
}

4.3、网络请求与异步数据

struct Post: Codable, Identifiable {let id: Intlet title: Stringlet body: String
}struct NetworkExampleView: View {@State private var posts: [Post] = []@State private var isLoading = false@State private var errorMessage: String?var body: some View {Group {if isLoading {ProgressView("加载中...").scaleEffect(1.5)} else if let error = errorMessage {VStack {Image(systemName: "exclamationmark.triangle").font(.largeTitle)Text(error)}.foregroundStyle(.red)} else {List(posts) { post inVStack(alignment: .leading) {Text(post.title).font(.headline)Text(post.body).font(.subheadline).foregroundStyle(.secondary).lineLimit(2)}}.refreshable {await fetchPosts()}}}.navigationTitle("网络请求示例").task {await fetchPosts()}}func fetchPosts() async {isLoading = trueerrorMessage = nildo {let url = URL(string: "https://jsonplaceholder.typicode.com/posts")!let (data, _) = try await URLSession.shared.data(from: url)posts = try JSONDecoder().decode([Post].self, from: data)} catch {errorMessage = "加载失败: \(error.localizedDescription)"}isLoading = false}
}

五、SwiftUI 最佳实践

1. 组件化设计：将UI拆分为小型可复用组件
2. 预览驱动开发：充分利用Xcode预览功能
3. 状态最小化：仅使必要的状态可变
4. 使用环境对象：跨视图层级共享数据
5. 性能优化：
   • 对列表项使用Identifiable协议
   • 避免在视图主体中执行繁重操作
   • 使用EquatableView优化视图更新

平台适配：

#if os(iOS)
// iOS特定代码
#elseif os(macOS)
// macOS特定代码
#endif

六、SwiftUI 开发环境要求

平台	最低版本要求
iOS	13.0+
macOS	10.15+
watchOS	6.0+
tvOS	13.0+
Xcode	11.0+

SwiftUI 代表了 Apple 开发生态的未来方向，通过声明式语法和响应式设计大大提高了开发效率。虽然学习曲线存在，但其强大的功能和开发体验使其成为构建 Apple 平台应用的首选框架。