how to display a search bar with SwiftUI

问题:

The new SwiftUI framework does not seem to provide a built-in search bar component. Should I use a UISearchController and wrap it in some way, or should I use a simple textfield and update the data according to the textfield input?

EDIT: the current workaround is to use a textfield as a searchBar. It is working very well, but it doesn't have the search icon

    import SwiftUI

    struct Search : View {

      let array = ["John","Lena","Steve","Chris","Catalina"]

      @State private var searchText = ""

      var body: some View {


          NavigationView{
            List{
                TextField("Type your search",text: $searchText)
                    .textFieldStyle(RoundedBorderTextFieldStyle())

                ForEach(array.filter{$0.hasPrefix(searchText) || searchText == ""}, id:\.self){searchText in
                    Text(searchText)
                }
            }
            .navigationBarTitle(Text("Search"))
        }


      }
    }

    struct Search_Previews : PreviewProvider {
      static var previews: some View {
        Search()
      }
    }

updated to work with Xcode 11.1

回答1:

Here is a pure swiftUI version, based on Antoine Weber's answer to his question above and what I found in this blog and this gist. It incorporates

• a clear button,
• a cancel button,
• resigning keyboard on dragging in the list and
• hiding the navigation view when the search text field is selected.

Resigning the keyboard on drag in the list can be realized using a method on UIApplication window following these answers. For easier handling I created an extension on UIApplication and view modifier for this extension and finally an extension to View:

extension UIApplication {
    func endEditing(_ force: Bool) {
        self.windows
            .filter{$0.isKeyWindow}
            .first?
            .endEditing(force)
    }
}

struct ResignKeyboardOnDragGesture: ViewModifier {
    var gesture = DragGesture().onChanged{_ in
        UIApplication.shared.endEditing(true)
    }
    func body(content: Content) -> some View {
        content.gesture(gesture)
    }
}

extension View {
    func resignKeyboardOnDragGesture() -> some View {
        return modifier(ResignKeyboardOnDragGesture())
    }
}

So the final modifier for resigning the keyboard is just one modifier that has to be placed on the list like this:

List {
    ForEach(...) {
        //...
    }
}
.resignKeyboardOnDragGesture()

The complete swiftUI project code for the search bar with a sample list of names is as follows. You can paste it into ContentView.swift of a new swiftUI project and play with it.

import SwiftUI

struct ContentView: View {
    let array = ["Peter", "Paul", "Mary", "Anna-Lena", "George", "John", "Greg", "Thomas", "Robert", "Bernie", "Mike", "Benno", "Hugo", "Miles", "Michael", "Mikel", "Tim", "Tom", "Lottie", "Lorrie", "Barbara"]
    @State private var searchText = ""
    @State private var showCancelButton: Bool = false

    var body: some View {

        NavigationView {
            VStack {
                // Search view
                HStack {
                    HStack {
                        Image(systemName: "magnifyingglass")

                        TextField("search", text: $searchText, onEditingChanged: { isEditing in
                            self.showCancelButton = true
                        }, onCommit: {
                            print("onCommit")
                        }).foregroundColor(.primary)

                        Button(action: {
                            self.searchText = ""
                        }) {
                            Image(systemName: "xmark.circle.fill").opacity(searchText == "" ? 0 : 1)
                        }
                    }
                    .padding(EdgeInsets(top: 8, leading: 6, bottom: 8, trailing: 6))
                    .foregroundColor(.secondary)
                    .background(Color(.secondarySystemBackground))
                    .cornerRadius(10.0)

                    if showCancelButton  {
                        Button("Cancel") {
                                UIApplication.shared.endEditing(true) // this must be placed before the other commands here
                                self.searchText = ""
                                self.showCancelButton = false
                        }
                        .foregroundColor(Color(.systemBlue))
                    }
                }
                .padding(.horizontal)
                .navigationBarHidden(showCancelButton) // .animation(.default) // animation does not work properly

                List {
                    // Filtered list of names
                    ForEach(array.filter{$0.hasPrefix(searchText) || searchText == ""}, id:\.self) {
                        searchText in Text(searchText)
                    }
                }
                .navigationBarTitle(Text("Search"))
                .resignKeyboardOnDragGesture()
            }
        }
    }
}



struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        Group {
           ContentView()
              .environment(\.colorScheme, .light)

           ContentView()
              .environment(\.colorScheme, .dark)
        }
    }
}

extension UIApplication {
    func endEditing(_ force: Bool) {
        self.windows
            .filter{$0.isKeyWindow}
            .first?
            .endEditing(force)
    }
}

struct ResignKeyboardOnDragGesture: ViewModifier {
    var gesture = DragGesture().onChanged{_ in
        UIApplication.shared.endEditing(true)
    }
    func body(content: Content) -> some View {
        content.gesture(gesture)
    }
}

extension View {
    func resignKeyboardOnDragGesture() -> some View {
        return modifier(ResignKeyboardOnDragGesture())
    }
}

The final result for the search bar, when initially displayed looks like this

and when the search bar is edited like this:

In Action:

回答2:

This YouTube video shows how it can be done. It boils down to:

struct SearchBar: UIViewRepresentable {

    @Binding var text: String

    class Coordinator: NSObject, UISearchBarDelegate {

        @Binding var text: String

        init(text: Binding<String>) {
            _text = text
        }

        func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {
            text = searchText
        }
    }
    func makeCoordinator() -> SearchBar.Coordinator {
        return Coordinator(text: $text)
    }

    func makeUIView(context: UIViewRepresentableContext<SearchBar>) -> UISearchBar {
        let searchBar = UISearchBar(frame: .zero)
        searchBar.delegate = context.coordinator
        searchBar.autocapitalizationType = .none
        return searchBar
    }

    func updateUIView(_ uiView: UISearchBar, context: UIViewRepresentableContext<SearchBar>) {
        uiView.text = text
    }
}

and then instead of

TextField($searchText)
              .textFieldStyle(.roundedBorder)

you use

SearchBar(text: $searchText)

回答3:

Many UIKit components currently do not have SwiftUI equivalents. In order to use them, you can create a wrapper as in https://developer.apple.com/tutorials/swiftui/creating-and-combining-views.

Basically, you make a SwiftUI class that conforms to UIViewRepresentable and implements makeUIView and updateUIView.