File Download Progress Bar Angular 6 [WORK]

How to create a file download progress bar with Angular 6 and Material Design

Downloading files is a common task for web applications that need to provide users with access to various types of data, such as PDFs, ZIPs, images, or videos. However, downloading files can also be a frustrating experience for users if they don’t know how long it will take, how much data has been transferred, or if there are any errors or interruptions. To improve the user experience and satisfaction, it is important to create a file download progress bar that shows the status and percentage of the download in a clear and attractive way.

In this article, I will show you how to create a file download progress bar with Angular 6 and Material Design, using the HttpClient module and the MatProgressBar component. I will also share some best practices and examples of file download progress bars in Angular 6 that you can use as inspiration for your own projects.

Prerequisites

To follow along with this article, you will need the following dependencies and tools:

Angular CLI: A command-line interface tool that helps you create and manage Angular projects. You can install it globally with npm install -g @angular/cli.
Angular Material: A UI component library that implements Google’s Material Design guidelines for Angular applications. You can install it with ng add @angular/material.
RxJS: A library for reactive programming that provides observables, operators, and other utilities for working with asynchronous data streams. It is already included as a dependency of Angular.

You will also need a server that provides some files to download. For this article, I will use https://file-examples.com/, which offers some sample files of different formats and sizes.

Creating the download service

The first step is to create a service that uses the HttpClient module to request a file from a server and track the download progress. The HttpClient module is an Angular service that provides a simplified API for HTTP requests. It supports various options and features, such as interceptors, headers, parameters, response types, error handling, and progress events.

To create a download service, we will use the Angular CLI command ng generate service download. This will generate a file called download.service.ts in the src/app folder. We will then add some code to this file to implement the following logic:

Create an Injectable decorator to mark the class as a service that can be injected into other components or services.
Create a constructor that injects an instance of HttpClient as a private property.
Create a method called downloadFile that takes a URL string as an argument and returns an observable of type Blob. A blob is a file-like object of immutable raw data that can represent any type of data, such as images, audio, or video. The observable will emit the blob data when the download is complete, or an error if the download fails.
Create a method called getDownloadProgress that takes a URL string as an argument and returns an observable of type number. The observable will emit the percentage of the download progress, from 0 to 100, based on the progress events emitted by the HttpClient request. The observable will also complete when the download is done, or error if the download fails.

The code for the download service is shown below:

@Injectable({   providedIn: 'root' }) export class DownloadService {   constructor(private http: HttpClient) { }   downloadFile(url: string): Observable {     return this.http.get(url, {responseType: 'blob'});   }   getDownloadProgress(url: string): Observable {     return this.http.get(url, {responseType: 'blob', reportProgress: true, observe: 'events'})       .pipe(         filter(event => event.type === HttpEventType.DownloadProgress || event.type === HttpEventType.Response),         map(event => {           if (event.type === HttpEventType.DownloadProgress) {             return Math.round(100 * event.loaded / event.total);           } else if (event.type === HttpEventType.Response) {             return 100;           }         })       );   } }

As you can see, we use the responseType option to specify that we want to receive a blob as the response. We also use the reportProgress option to enable tracking of progress events, and the observe option to get the full response object instead of just the body. We then use the RxJS operators filter and map to transform the response events into progress values.

Creating the download component

The next step is to create a component that uses the MatProgressBar component to display the download progress and the file name. The MatProgressBar component is a Material Design component that provides a horizontal bar to indicate the progress of an operation. It supports various modes, such as determinate, indeterminate, buffer, and query. It also supports accessibility features, such as aria-label and aria-valuemin/valuemax/valuenow attributes.

To create a download component, we will use the Angular CLI command ng generate component download. This will generate four files in the src/app/download folder: download.component.ts, download.component.html, download.component.css, and download.component.spec.ts. We will then add some code to these files to implement the following logic:

Create an @Input decorator to bind a property called fileUrl that will receive the URL of the file to download from the parent component.
Create a constructor that injects an instance of DownloadService as a private property.
Create two properties called fileName and progress that will store the name and percentage of the downloaded file.
Create a method called ngOnInit that will execute when the component is initialized. In this method, we will do the following:

Use the JavaScript URL API to extract the file name from the file URL and assign it to the fileName property.
Call the getDownloadProgress method of DownloadService with the file URL as an argument and subscribe to its observable. In the subscription callback, we will assign the progress value to the progress property.
Call the downloadFile method of DownloadService with the file URL as an argument and subscribe to its observable. In the subscription callback, we will use the JavaScript File API to create a blob URL from the blob data and use the Window API to open a new window with that URL. This will trigger the browser’s default download behavior and save the file to the user’s device.

Create a template file that uses the MatProgressBar component to display the download progress and the file name. We will use the mode attribute to set the mode to determinate, which means that the progress bar will show a specific value. We will also use the value attribute to bind the progress value from the component class. We will use some CSS styles to customize the appearance of the progress bar and the file name.

The code for the download component is shown below:

// download.component.ts import { Component, OnInit, Input } from '@angular/core'; import { DownloadService } from '../download.service'; @Component({   selector: 'app-download',   templateUrl: './download.component.html',   styleUrls: ['./download.component.css'] }) export class DownloadComponent implements OnInit {   @Input() fileUrl: string;   fileName: string;   progress: number;   constructor(private downloadService: DownloadService) { }   ngOnInit(): void {     this.fileName = new URL(this.fileUrl).pathname.split('/').pop();     this.downloadService.getDownloadProgress(this.fileUrl).subscribe(       progress => {         this.progress = progress;       },       error => {         console.error(error);       }     );     this.downloadService.downloadFile(this.fileUrl).subscribe(       blob => {         const blobUrl = URL.createObjectURL(blob);         window.open(blobUrl);       },       error => {         console.error(error);       }     );   } }

// download.component.html <div >   <mat-progress-bar mode="determinate" [value]="progress"></mat-progress-bar>   <p >{{fileName}}</p> </div>

// download.component.css .download-container {   width: 300px;   margin: 10px auto; } .mat-progress-bar {   height: 20px; } .file-name {   text-align: center;   font-weight: bold; }

Testing the download feature

To test the download feature, we need to use the download component in an app and provide some file URLs as inputs. For this article, I will use a simple app component that displays a list of file URLs and their formats and sizes. The app component will use the Angular Material components MatList and MatListItem to create a list of items, each containing a download component with a file URL as an input.

To create an app component, we will use the Angular CLI command ng generate component app. This will generate four files in the src/app/app folder: app.component.ts, app.component.html, app.component.css, and app.component.spec.ts. We will then add some code to these files to implement the following logic:

Create an array of objects called files that contains some sample file URLs and their formats and sizes. We will use some of the files from https://file-examples.com/.
Create a template file that uses the MatList and MatListItem components to display the files array as a list of items, each containing a download component with a file URL as an input. We will also use some CSS styles to customize the appearance of the list and its items.

The code for the app component is shown below:

// app.component.ts import { Component } from '@angular/core'; @Component({   selector: 'app-root',   templateUrl: './app.component.html',   styleUrls: ['./app.component.css'] }) export class AppComponent {   files = [     {       url: 'https://file-examples-com.github.io/uploads/2017/10/file-sample_150kB.pdf',       format: 'PDF',       size: '150 kB'     },     {       url: 'https://file-examples-com.github.io/uploads/2017/11/file_example_MP3_700KB.mp3', file download progress bar with Angular 6 and Material Design, using the HttpClient module and the MatProgressBar component. I have also shared some best practices and examples of file download progress bars in Angular 6 that you can use as inspiration for your own projects. Creating a file download progress bar in Angular 6 is a useful and easy way to enhance the user experience and satisfaction of your web applications. By using observables, error handling, and custom styles, you can create a file download progress bar that is responsive, reliable, and attractive. You can also explore other features and options of the HttpClient module and the MatProgressBar component to create more advanced and customized file download progress bars in Angular 6. I hope you enjoyed this article and learned something new. If you have any questions or feedback, please feel free to leave a comment below. Thank you for reading! FAQs
 
Here are some frequently asked questions about file download progress bars in Angular 6:



 
How can I cancel a file download in Angular 6?

One way to cancel a file download in Angular 6 is to use the takeUntil operator to unsubscribe from the observable when a certain condition is met. For example, you can create a Subject that emits a value when the user clicks on a cancel button, and then use the takeUntil operator to stop the download when that value is emitted. You can also use the finalize operator to perform some cleanup actions when the download is canceled.



How can I resume a file download in Angular 6?

One way to resume a file download in Angular 6 is to use the Range header to specify the byte range of the file that you want to request. For example, if you have already downloaded 50% of a 10 MB file, you can set the Range header to bytes=5000000- to request the remaining half of the file. You can also use the Content-Range header to check the byte range of the response. You will need to store the downloaded bytes and append them to the resumed bytes to create the complete file.



How can I show multiple file download progress bars in Angular 6?

One way to show multiple file download progress bars in Angular 6 is to use an array of objects that contains the file URLs and their progress values. You can then use the *ngFor directive to iterate over the array and create a download component for each item. You can also use the RxJS operators forkJoin, merge, or combineLatest to combine multiple observables of file downloads and track their progress.



How can I test a file download feature in Angular 6?

One way to test a file download feature in Angular 6 is to use a mock server that provides some sample files to download. You can use tools such as json-server, Mocky, or Postman to create a mock server that returns files with different formats and sizes. You can also use tools such as Jasmine, Karma, or Protractor to write unit tests, integration tests, or end-to-end tests for your file download feature.



How can I optimize a file download feature in Angular 6?

One way to optimize a file download feature in Angular 6 is to use compression techniques to reduce the size of the files that are transferred over the network. You can use tools such as gzip, brotli, or zstd to compress files on the server side and decompress them on the client side. You can also use tools such as webpack, rollup, or parcel to bundle and minify your code and assets for faster loading.












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