Bootstrap 4 and Angular: A Beginner's Guide to Customizing a Theme
Bootstrap 4 and Angular: A Beginner's Guide to Customizing a Theme
In this tutorial, learn how to quickly build and style new universal themes for your Angular apps using Bootstrap 4, as well as Sass and Kendo UI.
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If you have created new Angular projects from the Angular CLI, you'll know they come with a bare-bones UI layout. No UI framework or guidance is provided out-of-the-box. In this article, we'll look at how to add Bootstrap 4 in a new Angular project and style the application using Sass.
We'll install Bootstrap 4 using npm, wire up Bootstrap and highlight the differences between a CSS and Sass (.scss) configuration. We'll also install Kendo UI for Angular 's Bootstrap 4 theme and integrate our custom theme.
For details on what's new in Bootstrap 4, see the article What's New and What's Changed in Bootstrap 4 for an excellent overview.
ng new and Pre-processing
First, let's start with a new Angular project. If you haven't tried the Angular CLI tool yet, you may need to install it. The setup requires just a simple npm command, we'll use the "-g" parameter to install the tool globally. Note: this works on Mac, Windows, and Linux.
npm install -g @angular/cli
Once the Angular CLI is installed, it's time to create a new app. Creating a new app is as simple as running the ng new command, however, there's a very important option here that needs to be highlighted. The ng new command supports CSS pre-processor integration and my recommendation is to take advantage by using Sass (.scss). Supporting Sass in your project gives you additional flexibility since any valid CSS is also valid Sass - this means you can use each interchangeably. Even if you're not familiar with Sass, it won't get in your way, and it can be used as little or as much as needed. Additionally, Sass leaves room for Bootstrap customization that is not otherwise available with CSS through Sass variables. Adding Sass is as simple as specifying the option from the CLI.
ng new <project name> --style=scss
Installing and Wiring-up Bootstrap 4
There are quite a few methods for installing and setting up Bootstrap. Often the process changes from one platform to another, so for the scope of this article, we'll focus on setting up Bootstrap with Angular using the Angular CLI.
The Sass Bits
Now that we have a new Angular project, we'll need to install Bootstrap 4. We'll use npm to load the dependencies. If you only intend to use the Bootstrap grid layout without its UI components, you can exclude the
firstname.lastname@example.org popper.js@^1.12.3 dependencies as these are mainly used with Bootstrap's UI components.
npm install email@example.com firstname.lastname@example.org popper.js@^1.12.3
In the Angular project, open
styles.scss and add a reference the
bootstrap.scss file. Note: with Sass, the file extension isn't necessary when declaring a reference.
Alternatively, .scss files can be added in the angular-cli.json styles array. However, it's common practice to structure Sass using a single entry point, or manifest-like file. In this example, the
styles.scss file will be used to reference all of our Sass imports, giving us a single point of configuration for Sass.
/* using Sass */ @import "~bootstrap/scss/bootstrap";
The JS Bits
.angular-cli.json "scripts": [ "../node_modules/jquery/jquery.min.js", "../node_modules/popper.js/dist/umd/popper.min.js", "../node_modules/bootstrap/dist/js/bootstrap.min.js" ],
Bootstrap's Sass code is located in
/node_modules/bootstrap/scss/, and it's here that you'll find all of the settings for the Bootstrap framework in the file
_variables.scss. Digging through
_variables we can see all of the values that can be used to customize the theme and behavior of Bootstrap. We'll focus on customizing the color variables found under
// Color system at the top of the file. It's important to note that the
_variables file should not be changed directly as it can and will be overwritten during future updates or installs. Instead, each variable is marked with a Sass !default keyword. The
!default keyword can be considered the opposite of !important. This allows us to override the setting easily in our own code external to the
//// Color system//
$blue: #007bff !default;
$primary: $blue !default;
$theme-colors: () !default;
Before we begin customizing our Bootstrap theme, let's add some code so we can see our changes take effect. In the main app component template,
app.component.html, we'll add some HTML to render a Bootstrap badge, card, and button. For the button, we'll set the class to
btn btn-primary, which will give the button the primary theme color. The
badge will use the
badge badge-secondary class, thus giving it the secondary theme color. By default, the primary color is blue
#007bff and secondary is gray
<!-- app.component.html --> <div class="container"> <div class="row"> <div class="col-4"> <div class="card" > <div class="card-body"> <h4 class="card-title">Card title</h4> <p class="card-text">Some quick example text ...</p> <a href="#" class="btn btn-primary">Go somewhere</a> </div> </div> </div> <div class="col-8"> <h1>Example heading <span class="badge badge-secondary">New</span> </h1> </div> </div> </div>
The markup should render in the browser with a blue button and gray badge as seen below.
Let's customize the theme using Sass variables so that every instance of the "primary" and "secondary" colors are changed throughout the theme. To do this, we'll override the theme map variable.
We'll start by adding a new custom variables file to our project. Add a new folder named
scss then add a new file to the folder named
_myTheme.scss. The underscore in the file name identifies it as a "partial," a file that should be imported. In
_myTheme, we'll add a theme map called
$theme-colors will override the default variables, allowing us to customize the "primary," "secondary," and other theme colors. In addition, completely custom theme colors can be defined here.
For this example, we'll use a purple tone for "primary" and a teal tone for "secondary." Adding the key/values
"primary": rgb(132, 50, 155) and
"secondary": rgb(2, 188, 235) to the theme map will override all instances of these colors in Bootstrap.
//_myTheme.scss $theme-colors: ( "primary": #84329b, "secondary": #02bceb );
The custom variables are now defined but have yet to be added to our style sheet. We'll need to import
_myTheme into our main Sass file
styles.scss to complete the customization. In
styles.scss we'll use an @import statement to bring in
_myTheme. The import must be placed above the line importing Bootstrap to take effect. When using import, it's not necessary to include underscores - just as with .scss extensions, these are implied by the compiler.
//styles.scss @import "scss/myTheme"; @import "~bootstrap/scss/bootstrap";
Once the import is in place, the CSS will recompile with the new values. The markup should render in the browser with our new theme colors as seen below.
Kendo UI for Angular Customization
Now that we have a custom Bootstrap theme, let's expand the UI capabilities of our application by adding the Kendo UI for the Angular component library. When adding new components to our application, we would like them to integrate seamlessly into the design. Thankfully, Kendo UI for Angular has the ability to match the style of the existing Bootstrap components, and it can also bridge the themes together. In addition, the Progress Sass ThemeBuilder, a graphical theme builder, provides an intuitive interface for creating custom themes.
To begin, we'll add the Kendo UI Bootstrap theme which applies to all Kendo UI components. The Kendo UI Bootstrap theme is installed using the same process as before with npm and then importing it into the styles.scss file.
First, the theme is installed.
npm install --save @progress/kendo-theme-bootstrap
all.scss file is imported into
styles.scss. We'll use the @import statement just as before, ensuring that the imports are in the correct order. Custom variables should come first, followed by the Kendo UI theme, then finally Bootstrap.
/* using scss */ @import "scss/myTheme"; @import "~@progress/kendo-theme-bootstrap/scss/all"; @import "~bootstrap/scss/bootstrap";
We'll customize the theme using the Progress Sass ThemeBuilder. The ThemeBuilder provides an interactive experience for creating custom themes. Simply navigate to http://themebuilder.telerik.com/ and choose the Bootstrap 4 starting theme.
Use the color pickers to fine-tune the color scheme.
Once the colors have been chosen, we'll download the zipped theme files which contain our settings as Sass code in
To apply the theme to our project, simply copy the code from
/scss/myTheme or add the file directly to the project and revise the
myTheme import statement.
With the theme values added to our application, we might expect additional steps to map the Kendo UI theme variables to Bootstrap. However, since we're already using the Kendo UI Bootstrap theme, this mapping is included for us. With the Kendo UI Bootstrap theme, all components in the app, including Bootstrap components, share a single style and settings.
$base-theme:Bootstrap; $skin-name:brand2018; $accent: #84329b; $secondary: #02bceb; ... $series-f: #d9534f; // Automatically mapped to Bootstrap // $theme-colors: ( // "primary": $accent:, // "secondary": $secondary // );
After saving the new theme, we can add any components from the Kendo UI for the Angular library. The added components will receive the theme colors in
myTheme without further customization. For installation instructions for each Kendo UI component, refer to the component's documentation page.
In this example, the button and calendar components are installed and rendered in the browser. The buttons, badge, and calendar all render with a unified color scheme.
Installing and setting up Bootstrap with Angular is a relatively simple task once you understand the process. Using Sass enables us to quickly theme our application by leveraging Bootstrap's variable system. Using Kendo UI for Angular expands the UIs available to us, while the addition of the Kendo UI Bootstrap theme enables us to leverage Sass and create a unified theme across all of the components in our application.
If the examples above make sense for your next Angular application, then consider taking Kendo UI for Angular for a spin. The Kendo UI for Angular free trial is right here waiting for you.
Published at DZone with permission of Ed Charbeneau , DZone MVB. See the original article here.
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