使用AlamoFiredownloadProgress時UI鎖定

我正在嘗試創建下載進度條并在下載完成時同時顯示警報。

對于此任務，我將 AlamoFire 與 SwiftUI 結合使用，因為它使下載變得容易。但是，當我使用帶有 Published 變數的 ProgressView 跟蹤進度時，整個 UI 都會鎖定，我無法弄清楚如何修復它。

我嘗試將 downloadProgress 添加到單獨的 DispatchQueue，但我仍然必須從主執行緒更新 UI，否則 Xcode 會抱怨。

如何測驗附加的示例代碼：

• 點擊“開始下載”
• 等待 ProgressView 移動一點
• 單擊“顯示警報”按鈕
• 嘗試關閉警報，它不會關閉。

我將不勝感激任何幫助。

匯入 SwiftUI 匯入 Alamofire

struct ContentView: View {
    @StateObject var viewModel: ViewModel = ViewModel()
    @State private var showAlert = false

    var body: some View {
        VStack {
            Button("Show Alert") {
                showAlert.toggle()
            }
            
            Button("Start download") {
                viewModel.startDownload()
            }
            
            if viewModel.showProgressView {
                ProgressView("Downloading…", value: viewModel.downloadProgress, total: 1.0)
                    .progressViewStyle(.linear)
            }
        }
        .alert(isPresented: $showAlert) {
            Alert(
                title: Text("Text"),
                dismissButton: .cancel()
            )
        }
    }
}

class ViewModel: ObservableObject {
    @Published var currentDownload: DownloadRequest? = nil
    @Published var downloadProgress: Double = 0.0
    @Published var showProgressView: Bool = false
    
    func startDownload() {
        print("Function called!")
        
        showProgressView.toggle()
        
        let queue = DispatchQueue(label: "alamofire", qos: .utility)
        let destination = DownloadRequest.suggestedDownloadDestination(for: .documentDirectory)

        AF.download("https://speed.hetzner.de/10GB.bin", to: destination)
            .downloadProgress(queue: queue) { progress in
                print(progress.fractionCompleted)
                
                DispatchQueue.main.async {
                    self.downloadProgress = progress.fractionCompleted
                }
            }
            .response { response in
                print(response)
            }
    }
}

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

uj5u.com熱心網友回復：

這里的問題是您實際上是在向 UI 執行緒發送更新的垃圾郵件，因為 alamofire 經常呼叫提供的閉包downloadProgress（查看控制臺列印）。您需要稍微錯開 AF 進度的更新，以便按下按鈕解除警報可以注冊（在組合中，這將被稱為去抖動）。我在這里所做的是添加了一個小時間計數器，以便它每秒只更新進度1。這些更新之間的時間使 UI 執行緒可以自由地回應點擊等。

import SwiftUI
import Alamofire

struct ContentView: View {
    @StateObject var viewModel: ViewModel = ViewModel()
    @State private var showAlert = false

    var body: some View {
        VStack {
            Button("Show Alert") {
                showAlert.toggle()
            }
            
            Button("Start download") {
                viewModel.startDownload()
            }
            
            if viewModel.showProgressView {
                ProgressView("Downloading…", value: viewModel.downloadProgress, total: 1.0)
                    .progressViewStyle(.linear)
            }
        }
        .alert(isPresented: $showAlert) {
            Alert(
                title: Text("Text"),
                dismissButton: .cancel()
            )
        }
    }
}

class ViewModel: ObservableObject {
    @Published var currentDownload: DownloadRequest? = nil
    @Published var downloadProgress: Double = 0.0
    @Published var showProgressView: Bool = false
    
    func startDownload() {
        print("Function called!")
        
        showProgressView.toggle()
        
        let queue = DispatchQueue(label: "net", qos: .userInitiated)
        let destination = DownloadRequest.suggestedDownloadDestination(for: .documentDirectory)
        var last = Date()
        AF.download("https://speed.hetzner.de/10GB.bin", to: destination)
            .downloadProgress(queue:queue) { progress in
                print(progress.fractionCompleted)
                if Date().timeIntervalSince(last) > 1 {
                    last = Date()
                    DispatchQueue.main.async {
                        self.downloadProgress = progress.fractionCompleted
                    }
                }
            }
            .response { response in
//                print(response)
            }
    }
}

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

標籤：迅速 迅捷 阿拉莫火

上一篇：如何在Swift中檢測顏色是白色還是黑色

下一篇：如何在SwiftUI中啟動應用程式時呼叫具有用戶當前位置的API？[復制]