01 Composing Complex Interfaces - ly918/SwiftUI-Chinese-Documents GitHub Wiki

应用程序设计和布局

组合复杂界面

地标的首页显示一个滚动的分类列表，在每个分类中水平滚动地标。在构建此主导航时，您将探索组合视图如何适应不同的设备大小和方向。

学习时间：20分钟

下载地址：ComposingComplexInterfaces.zip

第一节添加首页

既然你已经拥有了地标应用程序所需的所有视图，现在是时候给它们一个首页了——一个统一视图页面。主视图不仅包含所有其他视图，还提供导航和显示地标的方法。

步骤1

在名为Home.swift的新文件中创建名为CategoryHome的自定义视图。

Home.swift

import SwiftUI

struct CategoryHome: View {
    var body: some View {
        Text("Landmarks Content")
    }
}

struct CategoryHome_Previews: PreviewProvider {
    static var previews: some View {
        CategoryHome()
    }
}

步骤2

修改scene delegate，使其显示新的CategoryHome视图而不是地标列表。

主视图是地标应用程序的根，因此它需要一种方式来呈现所有其他视图。

SceneDelegate.swift

import SwiftUI
import UIKit

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var window: UIWindow?

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
        // If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
        // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).

        // Use a UIHostingController as window root view controller
        if let windowScene = scene as? UIWindowScene {
            let window = UIWindow(windowScene: windowScene)
            window.rootViewController = UIHostingController(
                rootView: CategoryHome()
                    .environmentObject(UserData())
            )
            self.window = window
            window.makeKeyAndVisible()
        }
    }
}

步骤3

添加NavigationView以在地标中承载不同的视图。

您可以使用NavigationView以及NavigationLink实例和相关修饰符在应用程序中构建导航层级结构。

Home.swift

import SwiftUI

struct CategoryHome: View {
    var body: some View {
        NavigationView {
            Text("Landmarks Content")
        }
    }
}

struct CategoryHome_Previews: PreviewProvider {
    static var previews: some View {
        CategoryHome()
    }
}

步骤4

将导航栏的标题设置为“Featured”。

Home.swift

import SwiftUI

struct CategoryHome: View {
    var body: some View {
        NavigationView {
            Text("Landmarks Content")
                .navigationBarTitle(Text("Featured"))
        }
    }
}

struct CategoryHome_Previews: PreviewProvider {
    static var previews: some View {
        CategoryHome()
    }
}

第二节创建分类列表

Landmarks应用程序将所有分类显示在垂直列中的单独行中，以便于浏览。通过组合垂直和水平堆栈，并向列表中添加滚动条，就可以完成此操作。

步骤1

使用Dictionary结构的init（grouping:by:）方法将地标分组到类别中，输入地标的category属性。

初始化项目文件给每个示例地标预设了类别。

Home.swift

import SwiftUI

struct CategoryHome: View {
    var categories: [String: [Landmark]] {
        Dictionary(
            grouping: landmarkData,
            by: { $0.category.rawValue }
        )
    }
    
    var body: some View {
        NavigationView {
            Text("Landmarks Content")
                .navigationBarTitle(Text("Featured"))
        }
    }
}

struct CategoryHome_Previews: PreviewProvider {
    static var previews: some View {
        CategoryHome()
    }
}

步骤2

使用列表在地标中显示分类。

Landmark.Category会匹配列表中每一项name，这些项在其他类别中必须是唯一的，因为它是枚举。

Home.swift

import SwiftUI

struct CategoryHome: View {
    var categories: [String: [Landmark]] {
        Dictionary(
            grouping: landmarkData,
            by: { $0.category.rawValue }
        )
    }
    
    var body: some View {
        NavigationView {
            List {
                ForEach(categories.keys.sorted(), id: \.self) { key in
                    Text(key)
                }
            }
            .navigationBarTitle(Text("Featured"))
        }
    }
}

struct CategoryHome_Previews: PreviewProvider {
    static var previews: some View {
        CategoryHome()
    }
}

第三节添加地标行

地标在水平滚动的行中显示每个类别。添加一个新的视图类型来表示行，然后在新视图中显示该类别的所有地标。

步骤1

定义用于保存行内容的新自定义视图。

这个视图需要存储地标的类别信息，以及地标本身。

CategoryRow.swift

import SwiftUI

struct CategoryRow: View {
    var categoryName: String
    var items: [Landmark]
    
    var body: some View {
        Text(self.categoryName)
            .font(.headline)
    }
}

struct CategoryRow_Previews: PreviewProvider {
    static var previews: some View {
        CategoryRow(
            categoryName: landmarkData[0].category.rawValue,
            items: Array(landmarkData.prefix(3))
        )
    }
}

步骤2

更新CategoryHome的主体以将类别信息传递给新的行类型。

Home.swift

import SwiftUI

struct CategoryHome: View {
    var categories: [String: [Landmark]] {
        Dictionary(
            grouping: landmarkData,
            by: { $0.category.rawValue }
        )
    }
    
    var body: some View {
        NavigationView {
            List {
                ForEach(categories.keys.sorted(), id: \.self) { key in
                    CategoryRow(categoryName: key, items: self.categories[key]!)
                }
            }
            .navigationBarTitle(Text("Featured"))
        }
    }
}

struct CategoryHome_Previews: PreviewProvider {
    static var previews: some View {
        CategoryHome()
    }
}

步骤3

在HStack中显示该类别的地标。

CategoryRow.swift

import SwiftUI

struct CategoryRow: View {
    var categoryName: String
    var items: [Landmark]
    
    var body: some View {
        HStack(alignment: .top, spacing: 0) {
            ForEach(self.items) { landmark in
                Text(landmark.name)
            }
        }
    }
}

struct CategoryRow_Previews: PreviewProvider {
    static var previews: some View {
        CategoryRow(
            categoryName: landmarkData[0].category.rawValue,
            items: Array(landmarkData.prefix(3))
        )
    }
}

步骤4

通过指定一个frame(width:height:) 并在scrollView中包装stack，为行提供空间。

使用长数据样本更新视图预览，以便确保可以滚动。

CategoryRow.swift

import SwiftUI

struct CategoryRow: View {
    var categoryName: String
    var items: [Landmark]
    
    var body: some View {
        VStack(alignment: .leading) {
            Text(self.categoryName)
                .font(.headline)
                .padding(.leading, 15)
                .padding(.top, 5)
            
            ScrollView(.horizontal, showsIndicators: false) {
                HStack(alignment: .top, spacing: 0) {
                    ForEach(self.items) { landmark in
                        Text(landmark.name)
                    }
                }
            }
            .frame(height: 185)
        }
    }
}

struct CategoryRow_Previews: PreviewProvider {
    static var previews: some View {
        CategoryRow(
            categoryName: landmarkData[0].category.rawValue,
            items: Array(landmarkData.prefix(4))
        )
    }
}

第四节组成主页

地标应用程序的主页需要显示地标的简单信息，然后用户点击其中一个更多进入详情视图。

重新使用在Creating and Combining Views中的视图来创建更简单的视图预览，以显示地标的分类和特征。

步骤1

在CategoryRow旁边创建一个名为CategoryItem的新自定义视图，并用新视图替换Text视图。

CategoryRow.swift

import SwiftUI

struct CategoryRow: View {
    var categoryName: String
    var items: [Landmark]
    
    var body: some View {
        VStack(alignment: .leading) {
            Text(self.categoryName)
                .font(.headline)
                .padding(.leading, 15)
                .padding(.top, 5)
            
            ScrollView(.horizontal, showsIndicators: false) {
                HStack(alignment: .top, spacing: 0) {
                    ForEach(self.items) { landmark in
                        CategoryItem(landmark: landmark)
                    }
                }
            }
            .frame(height: 185)
        }
    }
}

struct CategoryItem: View {
    var landmark: Landmark
    var body: some View {
        VStack(alignment: .leading) {
            landmark.image
                .resizable()
                .frame(width: 155, height: 155)
                .cornerRadius(5)
            Text(landmark.name)
                .font(.caption)
        }
        .padding(.leading, 15)
    }
}

struct CategoryRow_Previews: PreviewProvider {
    static var previews: some View {
        CategoryRow(
            categoryName: landmarkData[0].category.rawValue,
            items: Array(landmarkData.prefix(4))
        )
    }
}

步骤2

在Home.swift中，添加一个名为FeaturedLandmarks的简单视图，该视图仅显示标记为isFeatured的地标。

在后面的教程中，您将把此视图转换为可交互的轮播视图。目前，它显示了一个裁剪和缩放后的预览图像。

Home.swift

import SwiftUI

struct CategoryHome: View {
    var categories: [String: [Landmark]] {
        Dictionary(
            grouping: landmarkData,
            by: { $0.category.rawValue }
        )
    }
    
    var featured: [Landmark] {
        landmarkData.filter { $0.isFeatured }
    }
    
    var body: some View {
        NavigationView {
            List {
                FeaturedLandmarks(landmarks: featured)
                    .scaledToFill()
                    .frame(height: 200)
                    .clipped()
                ForEach(categories.keys.sorted(), id: \.self) { key in
                    CategoryRow(categoryName: key, items: self.categories[key]!)
                }
            }
            .navigationBarTitle(Text("Featured"))
        }
    }
}

struct FeaturedLandmarks: View {
    var landmarks: [Landmark]
    var body: some View {
        landmarks[0].image.resizable()
    }
}

struct CategoryHome_Previews: PreviewProvider {
    static var previews: some View {
        CategoryHome()
    }
}

步骤3

在两种地标预览中将edge insets设置为零，以便内容可以延伸到屏幕边缘。

Home.swift

import SwiftUI

struct CategoryHome: View {
    var categories: [String: [Landmark]] {
        Dictionary(
            grouping: landmarkData,
            by: { $0.category.rawValue }
        )
    }
    
    var featured: [Landmark] {
        landmarkData.filter { $0.isFeatured }
    }
    
    var body: some View {
        NavigationView {
            List {
                FeaturedLandmarks(landmarks: featured)
                    .scaledToFill()
                    .frame(height: 200)
                    .clipped()
                    .listRowInsets(EdgeInsets())
                
                ForEach(categories.keys.sorted(), id: \.self) { key in
                    CategoryRow(categoryName: key, items: self.categories[key]!)
                }
                .listRowInsets(EdgeInsets())
            }
            .navigationBarTitle(Text("Featured"))
        }
    }
}

struct FeaturedLandmarks: View {
    var landmarks: [Landmark]
    var body: some View {
        landmarks[0].image.resizable()
    }
}

struct CategoryHome_Previews: PreviewProvider {
    static var previews: some View {
        CategoryHome()
    }
}

第五节在分区之间添加导航

现在，在主页中可以看到所有不同分类的地标，用户需要一种方法来访问应用程序中的每个部分。使用navigation和presentation Apis可以从主页导航到地标详情页，收藏夹和用户主页。

步骤1

在CategoryRow.swift中，用NavigationLink包装现有的CategoryItem。

类别项本身是按钮的label，其目的地是显示地标详情视图。

CategoryRow.swift

import SwiftUI

struct CategoryRow: View {
    var categoryName: String
    var items: [Landmark]
    
    var body: some View {
        VStack(alignment: .leading) {
            Text(self.categoryName)
                .font(.headline)
                .padding(.leading, 15)
                .padding(.top, 5)
            
            ScrollView(.horizontal, showsIndicators: false) {
                HStack(alignment: .top, spacing: 0) {
                    ForEach(self.items) { landmark in
                        NavigationLink(
                            destination: LandmarkDetail(
                                landmark: landmark
                            )
                        ) {
                            CategoryItem(landmark: landmark)
                        }
                    }
                }
            }
            .frame(height: 185)
        }
    }
}

struct CategoryItem: View {
    var landmark: Landmark
    var body: some View {
        VStack(alignment: .leading) {
            landmark.image
                .resizable()
                .frame(width: 155, height: 155)
                .cornerRadius(5)
            Text(landmark.name)
                .font(.caption)
        }
        .padding(.leading, 15)
    }
}

struct CategoryRow_Previews: PreviewProvider {
    static var previews: some View {
        CategoryRow(
            categoryName: landmarkData[0].category.rawValue,
            items: Array(landmarkData.prefix(4))
        )
    }
}

注意

在Xcode11 beta 6中，如果在列表中嵌套一个ScrollView，并且该ScrollView包含一个NavigationLink，那么当用户点击NavigationLink时，这些NavigationLink不会导航到目标视图。

步骤2

通过应用renderingMode（:）和foregroundColor（:）修饰符更改导航外观。

作为NavigationLink的label传递的文本使用环境的强调色进行渲染，而图像可能被作为template images进行渲染。您可以修改任一行为以最适合您的设计。

CategoryRow.swift

import SwiftUI

struct CategoryRow: View {
    var categoryName: String
    var items: [Landmark]
    
    var body: some View {
        VStack(alignment: .leading) {
            Text(self.categoryName)
                .font(.headline)
                .padding(.leading, 15)
                .padding(.top, 5)
            
            ScrollView(.horizontal, showsIndicators: false) {
                HStack(alignment: .top, spacing: 0) {
                    ForEach(self.items) { landmark in
                        NavigationLink(
                            destination: LandmarkDetail(
                                landmark: landmark
                            )
                        ) {
                            CategoryItem(landmark: landmark)
                        }
                    }
                }
            }
            .frame(height: 185)
        }
    }
}

struct CategoryItem: View {
    var landmark: Landmark
    var body: some View {
        VStack(alignment: .leading) {
            landmark.image
                .renderingMode(.original)
                .resizable()
                .frame(width: 155, height: 155)
                .cornerRadius(5)
            Text(landmark.name)
                .foregroundColor(.primary)
                .font(.caption)
        }
        .padding(.leading, 15)
    }
}

struct CategoryRow_Previews: PreviewProvider {
    static var previews: some View {
        CategoryRow(
            categoryName: landmarkData[0].category.rawValue,
            items: Array(landmarkData.prefix(4))
        )
    }
}

步骤3

在Home.swift中，点击选项卡栏中的简介图标后，添加一个模态视图以显示用户简介页面。

当showProfile状态变量设置为true时，SwiftUI显示用户简介占位符，当用户关闭模态时，将showProfile设置回false。

Home.swift

import SwiftUI

struct CategoryHome: View {
    var categories: [String: [Landmark]] {
        Dictionary(
            grouping: landmarkData,
            by: { $0.category.rawValue }
        )
    }
    
    var featured: [Landmark] {
        landmarkData.filter { $0.isFeatured }
    }
    
    @State var showingProfile = false

    var body: some View {
        NavigationView {
            List {
                FeaturedLandmarks(landmarks: featured)
                    .scaledToFill()
                    .frame(height: 200)
                    .clipped()
                    .listRowInsets(EdgeInsets())
                
                ForEach(categories.keys.sorted(), id: \.self) { key in
                    CategoryRow(categoryName: key, items: self.categories[key]!)
                }
                .listRowInsets(EdgeInsets())
            }
            .navigationBarTitle(Text("Featured"))
            .sheet(isPresented: $showingProfile) {
                Text("User Profile")
            }
        }
    }
}

struct FeaturedLandmarks: View {
    var landmarks: [Landmark]
    var body: some View {
        landmarks[0].image.resizable()
    }
}

struct CategoryHome_Previews: PreviewProvider {
    static var previews: some View {
        CategoryHome()
    }
}

步骤4

在导航栏中添加一个按钮，在点击时将showProfile从false切换为true。

Home.swift

import SwiftUI

struct CategoryHome: View {
    var categories: [String: [Landmark]] {
        .init(
            grouping: landmarkData,
            by: { $0.category.rawValue }
        )
    }
    
    var featured: [Landmark] {
        landmarkData.filter { $0.isFeatured }
    }
    
    @State var showingProfile = false
    
    var profileButton: some View {
        Button(action: { self.showingProfile.toggle() }) {
            Image(systemName: "person.crop.circle")
                .imageScale(.large)
                .accessibility(label: Text("User Profile"))
                .padding()
        }
    }

    var body: some View {
        NavigationView {
            List {
                FeaturedLandmarks(landmarks: featured)
                    .scaledToFill()
                    .frame(height: 200)
                    .clipped()
                    .listRowInsets(EdgeInsets())
                
                ForEach(categories.keys.sorted(), id: \.self) { key in
                    CategoryRow(categoryName: key, items: self.categories[key]!)
                }
                .listRowInsets(EdgeInsets())
            }
            .navigationBarTitle(Text("Featured"))
            .navigationBarItems(trailing: profileButton)
            .sheet(isPresented: $showingProfile) {
                Text("User Profile")
            }
        }
    }
}

struct FeaturedLandmarks: View {
    var landmarks: [Landmark]
    var body: some View {
        landmarks[0].image(forSize: 250).resizable()
    }
}

struct CategoryHome_Previews: PreviewProvider {
    static var previews: some View {
        CategoryHome()
    }
}

步骤5

通过添加导航链接完成主页，该链接指向可过滤所有地标的列表。

Home.swift

import SwiftUI

struct CategoryHome: View {
    var categories: [String: [Landmark]] {
        Dictionary(
            grouping: landmarkData,
            by: { $0.category.rawValue }
        )
    }
    
    var featured: [Landmark] {
        landmarkData.filter { $0.isFeatured }
    }
    
    @State var showingProfile = false
    
    var profileButton: some View {
        Button(action: { self.showingProfile.toggle() }) {
            Image(systemName: "person.crop.circle")
                .imageScale(.large)
                .accessibility(label: Text("User Profile"))
                .padding()
        }
    }

    var body: some View {
        NavigationView {
            List {
                FeaturedLandmarks(landmarks: featured)
                    .scaledToFill()
                    .frame(height: 200)
                    .clipped()
                    .listRowInsets(EdgeInsets())
                
                ForEach(categories.keys.sorted(), id: \.self) { key in
                    CategoryRow(categoryName: key, items: self.categories[key]!)
                }
                .listRowInsets(EdgeInsets())
                
                NavigationLink(destination: LandmarkList()) {
                    Text("See All")
                }
            }
            .navigationBarTitle(Text("Featured"))
            .navigationBarItems(trailing: profileButton)
            .sheet(isPresented: $showingProfile) {
                Text("User Profile")
            }
        }
    }
}

struct FeaturedLandmarks: View {
    var landmarks: [Landmark]
    var body: some View {
        landmarks[0].image.resizable()
    }
}

struct CategoryHome_Previews: PreviewProvider {
    static var previews: some View {
        CategoryHome()
    }
}

步骤6

在LandmarkList.swift中，删除包装地标列表的NavigationView，并将其添加到预览中。

在应用程序的环境中，LandmarkList将始终显示在Home.swift中声明的导航视图中。

LandmarkList.swift

import SwiftUI

struct LandmarkList: View {
    @EnvironmentObject var userData: UserData

    var body: some View {

        List {
            Toggle(isOn: $userData.showFavoritesOnly) {
                Text("Favorites only")
            }

            ForEach(userData.landmarks) { landmark in
                if !self.userData.showFavoritesOnly || landmark.isFavorite {
                    NavigationLink(destination: LandmarkDetail(landmark: landmark)) {
                        LandmarkRow(landmark: landmark)
                    }
                }
            }
        }
        .navigationBarTitle(Text("Landmarks"))

    }
}

struct LandmarkList_Previews: PreviewProvider {
    static var previews: some View {
        NavigationView {
            LandmarkList()
                .environmentObject(UserData())
        }
    }
}

01 Composing Complex Interfaces - ly918/SwiftUI-Chinese-Documents GitHub Wiki

应用程序设计和布局

组合复杂界面

第一节 添加首页

步骤1

步骤2

步骤3

步骤4

第二节 创建分类列表

步骤1

步骤2

第三节 添加地标行

步骤1

步骤2

步骤3

步骤4

第四节 组成主页

步骤1

步骤2

步骤3

第五节 在分区之间添加导航

步骤1

步骤2

步骤3

步骤4

步骤5

步骤6

第一节添加首页

第二节创建分类列表

第三节添加地标行

第四节组成主页

第五节在分区之间添加导航