iOS swiftUI的实用举例

SwiftUI 是 Apple 推出的声明式 UI 框架，以下是一些实用技巧和最佳实践，可以帮助你更高效地开发 iOS/macOS/watchOS/tvOS 应用。

1. 布局技巧

灵活的空间占用

// 使用 Spacer 填充可用空间 
HStack {Text("Left")Spacer() // 填充中间空间 Text("Right")
}// 使用 frame 控制视图大小 
Text("Hello").frame(maxWidth: .infinity, maxHeight: .infinity) // 填充父视图 .background(Color.yellow)

条件显示视图

@State private var isShowing = false var body: some View {VStack {if isShowing {Text("Visible")} else {EmptyView()}// 或者使用更简洁的方式 isShowing ? Text("Visible") : nil }
}

2. 状态管理

使用 @State 和 @Binding

struct ParentView: View {@State private var text = ""var body: some View {VStack {Text("Parent: \(text)")ChildView(text: $text) // 传递绑定 }}
}struct ChildView: View {@Binding var text: String var body: some View {TextField("Enter text", text: $text)}
}

使用 @ObservedObject 和 @Published

class UserSettings: ObservableObject {@Published var score = 0 
}struct ContentView: View {@ObservedObject var settings = UserSettings()var body: some View {VStack {Text("Score: \(settings.score)")Button("Increase") {settings.score += 1 }}}
}

3. 列表与导航

动态列表

struct ContentView: View {let items = ["Apple", "Banana", "Cherry"]var body: some View {List(items, id: \.self) { item in Text(item)}}
}

带删除和移动功能的列表

struct ContentView: View {@State private var items = ["Apple", "Banana", "Cherry"]var body: some View {NavigationView {List {ForEach(items, id: \.self) { item in Text(item)}.onDelete(perform: deleteItems).onMove(perform: moveItems)}.navigationBarItems(trailing: EditButton())}}func deleteItems(at offsets: IndexSet) {items.remove(atOffsets: offsets)}func moveItems(from source: IndexSet, to destination: Int) {items.move(fromOffsets: source, toOffset: destination)}
}

4. 动画与过渡

简单动画

@State private var scale: CGFloat = 1.0 var body: some View {Button("Tap Me") {withAnimation(.spring()) {scale = scale == 1.0 ? 2.0 : 1.0 }}.scaleEffect(scale)
}

自定义过渡

@State private var showDetails = false var body: some View {VStack {Button("Toggle") {withAnimation {showDetails.toggle()}}if showDetails {Text("Details").transition(.asymmetric(insertion: .move(edge: .leading),removal: .move(edge: .trailing)))}}
}

5. 实用修饰符

同时应用多个修饰符

Text("Hello").modifier(MyCustomModifier())// 或者使用扩展 
extension View {func customStyle() -> some View {self .padding().background(Color.blue).foregroundColor(.white).cornerRadius(10)}
}Text("Hello").customStyle()

条件修饰符

@State private var isHighlighted = false var body: some View {Text("Hello").foregroundColor(isHighlighted ? .red : .blue).onTapGesture {isHighlighted.toggle()}
}

6. 性能优化

使用 Lazy 视图

ScrollView {LazyVStack { // 只渲染可见项 ForEach(0..<1000) { index in Text("Row \(index)")}}
}

使用 EquatableView 避免不必要重绘

struct UserView: View, Equatable {let user: User var body: some View {Text(user.name)}static func == (lhs: UserView, rhs: UserView) -> Bool {lhs.user.id == rhs.user.id }
}// 使用 
UserView(user: someUser).equatable()

与其他框架集成

与 UIKit 集成

struct MyUIKitView: UIViewRepresentable {func makeUIView(context: Context) -> UIActivityIndicatorView {UIActivityIndicatorView(style: .large)}func updateUIView(_ uiView: UIActivityIndicatorView, context: Context) {uiView.startAnimating()}
}// 使用 
MyUIKitView()

与 Core Data 集成

struct ContentView: View {@Environment(\.managedObjectContext) private var viewContext @FetchRequest(sortDescriptors: [NSSortDescriptor(keyPath: \Item.timestamp, ascending: true)],animation: .default)private var items: FetchedResults<Item>var body: some View {List {ForEach(items) { item in Text("Item at \(item.timestamp!, formatter: itemFormatter)")}.onDelete(perform: deleteItems)}}private func deleteItems(offsets: IndexSet) {withAnimation {offsets.map { items[$0] }.forEach(viewContext.delete)try? viewContext.save()}}
}

8. 调试技巧

调试视图层次结构

Text("Hello").debug() // 添加这个修饰符查看视图信息 extension View {func debug() -> Self {print(Mirror(reflecting: self).subjectType)return self }
}

预览多个设备

struct ContentView_Previews: PreviewProvider {static var previews: some View {Group {ContentView().previewDevice("iPhone 13")ContentView().previewDevice("iPhone SE (2nd generation)")ContentView().previewDevice("iPad Pro (12.9-inch) (5th generation)")}}
}