UIProgressView 不更新进度

Question

我的应用程序有一个导入功能，它获取来自另一个 ViewController 的字符串数据并使用展开转场传递它。在目标 ViewController 中，有一个 ProgressView 添加到了 AlertView，它应该针对字符串的每个导入组件进行更新，但进度条永远不会更新。

这是目标 ViewController：

import UIKit

class MoviesViewController: UITableViewController {

    var progressView: UIProgressView!
    [...]

    @IBAction func addImportedMovies(_ segue: UIStoryboardSegue) {
        if let importViewController = segue.source as? ImportViewController, let importedMovielist = importViewController.movies {
            importedMovies = importedMovielist.reversed()
            if importedMovies != [] {
                self.parent?.dismiss(animated: true, completion: nil)
                let alertView = UIAlertController(title: "Please wait", message: "Data is being processed...", preferredStyle: .alert)
                present(alertView, animated: true, completion: { [self] in
                    let margin:CGFloat = 8.0
                    let rect = CGRect(x: margin, y: 72.0, width: alertView.view.frame.width - margin * 2.0 , height: 2.0)
                    progressView = UIProgressView(frame: rect)
                    progressView.tintColor = view.tintColor
                    alertView.view.addSubview(progressView)
                    progressView.isHidden = false
                    DispatchQueue.main.async { [self] in
                        progressView.progress = 0.0/Float(importedMovies.count)
                        for (i, movie) in importedMovies.enumerated() {
                            progressView.progress = Float(i+1)/Float(importedMovies.count)
                            print(progressView.progress)
                            [...updating DataSource and TableView]
                        }
                        [...]
                        alertView.dismiss(animated: true, completion: nil)
                        importedMovies = []
                    }
                })
            }
        }
    }
}

我尝试使用 DispatchQueue.global，将代码移至 ViewWillAppear 以及我在类似线程中看到的各种其他更改，但没有成功。

Answer 1

试试这个：

@IBAction func addImportedMovies(_ segue: UIStoryboardSegue) {
    if let importViewController = segue.source as? ImportViewController, let importedMovielist = importViewController.movies {
        importedMovies = importedMovielist.reversed()

        if !importedMovies.isEmpty {
            self.parent?.dismiss(animated: true, completion: nil)

            // Create an alert controller
            let alertView = UIAlertController(title: "Please wait", message: "Data is being processed...", preferredStyle: .alert)

            // Add a progress view to the alert controller
            let progressView = UIProgressView(progressViewStyle: .default)
            alertView.view.addSubview(progressView)

            // Present the alert controller
            present(alertView, animated: true, completion: { [self] in
                // Perform UI updates on the main thread
                DispatchQueue.main.async { [self] in
                    progressView.progress = 0.0

                    // Iterate through importedMovies and update progress view
                    for (i, movie) in importedMovies.enumerated() {
                        progressView.progress = Float(i + 1) / Float(importedMovies.count)
                        print(progressView.progress)
                        // [...updating DataSource and TableView]
                    }

                    // Other updates...
                    alertView.dismiss(animated: true, completion: nil)
                    importedMovies = []
                }
            })
        }
    }
}