在 SwiftUI 中向 NavigationView 添加搜索栏

Question

我正在使用 SwiftUI 创建一个项目，并希望在导航栏中添加一个搜索栏，就像原生设置应用程序、邮件应用程序等中存在的那样。

我尝试了一些方法，但无法完全发挥作用。以下代码运行良好，但即使包含navigationController.navigationItem.hidesSearchBarWhenScrolling = false，搜索栏也不会显示（我尝试向上滚动）。任何帮助将不胜感激。

//
//  ContentView.swift
//  SwiftUITest
//
//  Created by me on 1/7/20.
//  Copyright © 2020 me. All rights reserved.
//

import SwiftUI

struct HomeView: View {
    var body: some View {
        ScrollView {
            HStack {
                Spacer(minLength: 0)

                Text("Hello World")

                Spacer(minLength: 0)
            }
        }
        .navigationBarTitle(Text("Search"))
    }
}

struct SecondView: View {
    var body: some View {
        return Text("Second View")
    }
}

struct CustomUIViewControllerRepresentation: UIViewControllerRepresentable {
    typealias UIViewControllerType = UINavigationController

    func makeUIViewController(context: Context) -> UINavigationController {
        let viewController = UIHostingController(rootView: HomeView())

        let navigationController = UINavigationController(rootViewController: viewController)
        navigationController.navigationBar.prefersLargeTitles = true

        let searchController = UISearchController()
        navigationController.navigationItem.searchController = searchController

        return navigationController
    }

    func updateUIViewController(_ uiViewController: UINavigationController, context: Context) {

    }
}


struct ContentView: View {
    var body: some View {
        CustomUIViewControllerRepresentation()
    }
}

Answer 1

（编辑）iOS 15：

iOS 15 添加了新属性.searchable()。您可能应该改用它。

原文：

如果有人还在寻找，我发了a package 来解决这个问题，因为我找到的所有其他解决方案都有一些问题。

我还在这里为那些不喜欢链接或只想复制/粘贴的人提供完整的相关源代码。

扩展名：

// Copyright © 2020 thislooksfun
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the “Software”), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

import SwiftUI
import Combine

public extension View {
    public func navigationBarSearch(_ searchText: Binding<String>) -> some View {
        return overlay(SearchBar(text: searchText).frame(width: 0, height: 0))
    }
}

fileprivate struct SearchBar: UIViewControllerRepresentable {
    @Binding
    var text: String
    
    init(text: Binding<String>) {
        self._text = text
    }
    
    func makeUIViewController(context: Context) -> SearchBarWrapperController {
        return SearchBarWrapperController()
    }
    
    func updateUIViewController(_ controller: SearchBarWrapperController, context: Context) {
        controller.searchController = context.coordinator.searchController
    }
    
    func makeCoordinator() -> Coordinator {
        return Coordinator(text: $text)
    }
    
    class Coordinator: NSObject, UISearchResultsUpdating {
        @Binding
        var text: String
        let searchController: UISearchController
        
        private var subscription: AnyCancellable?
        
        init(text: Binding<String>) {
            self._text = text
            self.searchController = UISearchController(searchResultsController: nil)
            
            super.init()
            
            searchController.searchResultsUpdater = self
            searchController.hidesNavigationBarDuringPresentation = true
            searchController.obscuresBackgroundDuringPresentation = false
            
            self.searchController.searchBar.text = self.text
            self.subscription = self.text.publisher.sink { _ in
                self.searchController.searchBar.text = self.text
            }
        }
        
        deinit {
            self.subscription?.cancel()
        }
        
        func updateSearchResults(for searchController: UISearchController) {
            guard let text = searchController.searchBar.text else { return }
            self.text = text
        }
    }
    
    class SearchBarWrapperController: UIViewController {
        var searchController: UISearchController? {
            didSet {
                self.parent?.navigationItem.searchController = searchController
            }
        }
        
        override func viewWillAppear(_ animated: Bool) {
            self.parent?.navigationItem.searchController = searchController
        }
        override func viewDidAppear(_ animated: Bool) {
            self.parent?.navigationItem.searchController = searchController
        }
    }
}

用法：

import SwiftlySearch

struct MRE: View {
  let items: [String]

  @State
  var searchText = ""

  var body: some View {
    NavigationView {
      List(items.filter { $0.localizedStandardContains(searchText) }) { item in
        Text(item)
      }.navigationBarSearch(self.$searchText)
    }
  }
}

Answer 2

试试这个：

-> 缺少这一行：viewController.navigationItem.searchController = searchController

 func makeUIViewController(context: Context) -> UINavigationController {
        let viewController = UIHostingController(rootView: HomeView())

        let navigationController = UINavigationController(rootViewController: viewController)
        navigationController.navigationBar.prefersLargeTitles = true

        let searchController = UISearchController()
        navigationController.navigationItem.searchController = searchController


        viewController.navigationItem.searchController = searchController

        return navigationController
    }