ProgressView

Posted on March 15, 2021



A ProgressView represents completion of a task or the occurance of an activity with an unknown completion time. A default value of 1.0 is used for the total value when tracking completion progress. As the example demonstrates below, different configurations of a progress view are possible.

progress view

import SwiftUI

struct ContentView: View {
    var body: some View {
        VStack(spacing: 30) {
            ProgressView()

            ProgressView("Loading...")

            ProgressView(value: 0.3)

            ProgressView(value: 40, total: 100)

            ProgressView(value: 0.55) {
                Label("Loading", systemImage: "bolt.fill")
            }

            ProgressView(value: 0.25, label: {
                Label("Loading", systemImage: "bolt.fill")
            }, currentValueLabel: {
                Text("0.25")
            })

            ProgressView(value: 10.0, total: 100.0, label: {
                Label("Download", systemImage: "icloud.and.arrow.down")
            }, currentValueLabel: {
                HStack {
                    Text("0")
                    Spacer()
                    Text("50")
                    Spacer()
                    Text("100")
                }
            })
        }
        .padding()
        .frame(width: 400, height: 500)
    }
}

The next example uses a state variable x to update the progress view by 10 when the “Add 10” button is clicked. A progress view is often associated with a background task; consequently, the progress view must be updated on the main thread. This is demonstrated with the “Add 20 bg” button in the example shown below.

progress view 2

import SwiftUI

struct ContentView: View {

    @State private var x = 0.0

    var body: some View {
        VStack {
            ProgressView(
                "Downloading... \(String(format: "%.0f", x))%",
                value: x,
                total: 100.0
            )

            // Increase progress bar by 10
            Button("Add 10") {
                if x < 100.0 {
                    x += 10.0
                }
            }

            // Increase progress bar by 20 using value from background thread
            Button("Add 20 bg") {
                DispatchQueue.global(qos: .background).async {
                    let z = 10.0
                    DispatchQueue.main.async {
                        if x < 100.0 {
                            x += 10.0 + z
                        }
                    }
                }
            }
        }
        .padding()
        .frame(width: 400, height: 300)
    }
}


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Gavin Wiggins © 2021