快速警报弹出进度栏

Question

I'm trying to implement an alert message showing a progress bar during a download.

I found this code:

let alertView = UIAlertController(title: "Please wait", message: "Need to download some files.", preferredStyle: .Alert)
alertView.addAction(UIAlertAction(title: "Cancel", style: .Cancel, handler: nil))


presentViewController(alertView, animated: true, completion: {
//  Add your progressbar after alert is shown (and measured)
let margin:CGFloat = 8.0
let rect = CGRectMake(margin, 72.0, alertView.view.frame.width - margin * 2.0 , 2.0)
let progressView = UIProgressView(frame: rect)
progressView.progress = 0.5
progressView.tintColor = UIColor.blueColor()
alertView.view.addSubview(progressView)
})

But I don't know how to update the progress (progressView.progress) during processing and more important how to exit from this alert when download is finished.

Any help will be appreciated!

Answer 1

I'm sure there's a better answer to the progress bar... But my solution is to know how may items must be loaded (ie some variable "total_item), increment the number completed (numDownloaded) and calculate the percentage based on how many have loaded, then update that percentage.

Dismissing the UIAlertController is easy. Simply add:

let okAction = UIAlertAction(title: "Okay", style: UIAlertActionStyle.default, handler: {action in self.dismiss(animated: true, completion: nil)})
alertView.addAction(okAction)

This will add an "Okay" button, which will dismiss the view controller. Perhaps you can add a closure which only enables the "Okay" UIAlertAction when the load is complete.

Answer 2

At the moment it works for me like this in the code below. The alert view and progress view I declared as vars with global access, that way I could change the progress as the download goes on, I dismiss the alert after the download task completes.

I am implementing the following:

• URLSessionDelegate
• URLSessionTaskDelegate
• URLSessionDownloadDelegate

For more information, posted sample code below:

var globalAlert: UIAlertController! //with global access
var globalProgressView: UIProgressView! //with global access

//flags
var downloading: Bool = false //true if we have a download in progress
var globalAlertShowing = false //true if global alert is showing

func urlSession(_ session: URLSession,
                downloadTask: URLSessionDownloadTask,
                didWriteData bytesWritten: Int64,
                totalBytesWritten: Int64,
                totalBytesExpectedToWrite: Int64){

    if totalBytesExpectedToWrite > 0 {
        let progress = Float(totalBytesWritten) / Float(totalBytesExpectedToWrite)
        print("Progress (ByteCountFormatter.string(fromByteCount: progress, countStyle: ByteCountFormatter.CountStyle.decimal))")
        var humanReadableFileSize: String = ByteCountFormatter.string(fromByteCount: Int64(totalBytesWritten), countStyle: ByteCountFormatter.CountStyle.decimal)
        print("total byte written: \(humanReadableFileSize)")

        if(globalAlertShowing){
            DispatchQueue.main.async {
                self.globalAlert.message = "\(humanReadableFileSize)"
                self.globalProgressView.progress = progress
            }
        }


    }

}