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Luis Bogges
Luis Bogges

Show the Download Status of a File in Swift with a Progress Bar


Download Progress Bar Swift: How to Create and Customize It




Have you ever wanted to show your users how much time or data is left for downloading a file or an image in your app? If so, you might need a download progress bar. A download progress bar is a graphical indicator that displays the percentage of completion of a download operation. In this article, you will learn what a download progress bar is, why you should use it, and how to create and customize it in Swift.


Introduction




What is a download progress bar?




A download progress bar is a UI component that shows the progress of a download operation. It usually consists of two parts: a horizontal bar that fills up as the download progresses, and a label that shows the numerical value of the progress, such as 50% or 10 MB out of 20 MB. A download progress bar can also have other features, such as a cancel button, a pause button, or an error message.




download progress bar swift



Why use a download progress bar?




A download progress bar can provide several benefits for your app and your users. Here are some of them:


  • It can improve the user experience by providing feedback and reducing uncertainty. Users can see how much time or data is left for the download, and whether the download is successful or not.



  • It can increase user engagement and retention by creating anticipation and satisfaction. Users can feel more motivated and rewarded when they see the progress of their download.



  • It can prevent user frustration and confusion by handling errors and interruptions. Users can see if there is any problem with the download, such as network failure or low battery, and take appropriate actions.



How to create a download progress bar in Swift?




There are different ways to create a download progress bar in Swift, but one of the most common and simple ways is to use URLSession and UIProgressView. URLSession is a class that provides an API for downloading and uploading data from and to a server. UIProgressView is a class that provides a standard progress bar for iOS apps. You can use these two classes together to create a basic download progress bar in Swift.


Creating a Download Progress Bar with URLSession




Setting up the UI




To set up the UI for your download progress bar, you need to add a UIProgressView and a UILabel to your storyboard or code. You can also add other UI elements, such as buttons or images, depending on your design. For example, you can add a UIButton to start or cancel the download, and an UIImageView to display the downloaded image. You also need to create outlets and actions for your UI elements in your view controller class.


Creating a URLSession data task




To create a URLSession data task for your download operation, you need to use the URLSession class and its dataTask(with:completionHandler:) method. This method takes two parameters: an URL that specifies the location of the file or image you want to download, and a completion handler that executes when the download is finished or failed. You also need to set the delegate property of your URLSession object to self, so that you can implement the delegate methods that report the progress of the download.


Implementing the URLSession delegate methods




To implement the URLSession delegate methods that report the progress of the download, you need to conform to the URLSessionDataDelegate protocol in your view controller class. This protocol defines several methods that are called when certain events occur during the data transfer. The most important methods for your download progress bar are: - urlSession(_:dataTask:didReceive:completionHandler:): This method is called when the data task receives the initial response from the server. You can use this method to check the status code and the expected content length of the response, and to decide whether to continue or cancel the download. - urlSession(_:dataTask:didReceive:): This method is called when the data task receives a portion of data from the server. You can use this method to append the received data to a data object, and to calculate and update the progress of the download. - urlSession(_:task:didCompleteWithError:): This method is called when the data task finishes or fails. You can use this method to handle any error that occurred during the download, and to perform any final actions, such as converting the data object to an image and displaying it on the image view. Updating the progress bar value and label




To update the progress bar value and label, you need to use the UIProgressView class and its progress and progressTintColor properties. The progress property is a float value that represents the fraction of the download that is completed, ranging from 0.0 to 1.0. The progressTintColor property is a UIColor value that represents the color of the filled portion of the progress bar. You can set these properties in your URLSession delegate methods, using the DispatchQueue.main.async method to ensure that the UI updates are performed on the main thread.