列出重新加载动画故障答案

【问题标题】：List reload animation glitches列出重新加载动画故障
【发布时间】：2020-01-05 16:47:15
【问题描述】：

所以我有一个列表，当用户填写搜索关键字时会发生变化，当没有结果时，所有单元格都会崩溃，并且不知何故它们会飞到第一部分，这看起来很丑陋。我的代码中有错误还是这是预期的 SwiftUI 行为？谢谢。

import SwiftUI

struct ContentView: View {

    @ObservedObject var viewModel = ViewModel(photoLibraryService: PhotoLibraryService.shared)

    var body: some View {
        NavigationView {
            List {
                Section {
                    TextField("Enter Album Name", text: $viewModel.searchText)
                }
                Section {
                    if viewModel.libraryAlbums.count > 0 {
                        ForEach(viewModel.libraryAlbums) { libraryAlbum -> Text in
                            let title = libraryAlbum.assetCollection.localizedTitle ?? "Album"
                            return Text(title)
                        }
                    }
                }
            }.listStyle(GroupedListStyle())
                .navigationBarTitle(
                    Text("Albums")
                ).navigationBarItems(trailing: Button("Add Album", action: {
                        PhotoLibraryService.shared.createAlbum(withTitle: "New Album \(Int.random(in: 1...100))")
                }))
        }.animation(.default)
    }
}

【问题讨论】：

你想把结果放在第一项吗？那么你需要进行排序而不是过滤
@ErnistIsabekov 不，我想过滤以显示结果。最终结果不是问题，而是从完整列表到结果的转换。您会看到当单元格折叠时，它会飞到顶部以超出其部分。这只是一瞬间的动画错误，但在设备上很明显。

标签： ios swift swiftui combine

【解决方案1】：

1) 你必须使用一些去抖动来减少刷新列表的需要，同时在搜索字段中输入

2) 禁用行动画

第二部分是最难的部分。诀窍是通过设置它的 id 来强制重新创建一些视图。

这是简单应用程序的代码（能够测试这个想法）

import SwiftUI
import Combine

class Model: ObservableObject {
    @Published var text: String = ""
    @Published var debouncedText: String = ""
    @Published var data = ["art", "audience", "association", "attitude", "ambition", "assistance", "awareness", "apartment", "artisan", "airport", "atmosphere", "actor", "army", "attention", "agreement", "application", "agency", "article", "affair", "apple", "argument", "analysis", "appearance", "assumption", "arrival", "assistant", "addition", "accident", "appointment", "advice", "ability", "alcohol", "anxiety", "ad", "activity"].map(DataRow.init)
    var filtered: [DataRow] {
        data.filter { (row) -> Bool in
            row.txt.lowercased().hasPrefix(debouncedText.lowercased())
        }
    }

    var id: UUID {
        UUID()
    }

    private var store = Set<AnyCancellable>()
    init(delay: Double) {
        $text
            .debounce(for: .seconds(delay), scheduler: RunLoop.main)
            .sink { [weak self] (s) in
            self?.debouncedText = s
        }.store(in: &store)
    }
}

struct DataRow: Identifiable {
    let id = UUID()
    let txt: String
    init(_ txt: String) {
        self.txt = txt
    }
}

struct ContentView: View {

    @ObservedObject var search = Model(delay: 0.5)

    var body: some View {

        NavigationView {
            VStack(alignment: .leading) {

                TextField("filter", text: $search.text)
                    .padding(.vertical)
                    .padding(.horizontal)

                List(search.filtered) { (e) in
                    Text(e.txt)
                }.id(search.id)
            }.navigationBarTitle("Navigation")
        }
    }
}


struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

我对结果很满意

【讨论】：