How to toggle dark mode in Angular

Question

I am trying to toggle the dark mode when a user toggles the switch, which is in the header component. See image below:

<nav class="navbar navbar-expand-lg navbar-light bg-light">
    <a class="navbar-brand" href="#">Navbar</a>
    <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNavAltMarkup" aria-controls="navbarNavAltMarkup" aria-expanded="false" aria-label="Toggle navigation">
      <span class="navbar-toggler-icon"></span>
    </button>
    <div class="collapse navbar-collapse" id="navbarNavAltMarkup">
      <div class="navbar-nav">
        <a class="nav-item nav-link active" href="/">Home <span class="sr-only">(current)</span></a>
        <a class="nav-item nav-link" href="/about">About</a>
        <a class="nav-item nav-link" href="/contact">Contact</a>
        <a class="nav-item nav-link" href="/resume">Resume</a>
      </div>
    </div>
    <div class="custom-control custom-switch">
        <input (change)="onChangeToggle()" type="checkbox" class="custom-control-input" id="toggleTheme">
        <label class="custom-control-label" for="toggleTheme">Dark Mode</label>
      </div>
  </nav>

My header component ts file holds a boolean value called setDark which is triggered in an event emitter through the Output decorator :

// header.component.ts

import { Component, OnInit , Output, EventEmitter} from '@angular/core';

@Component({
  selector: 'app-header',
  templateUrl: './header.component.html',
  styleUrls: ['./header.component.css']
})
export class HeaderComponent implements OnInit {

  @Output() mode = new EventEmitter<boolean>();

  setDark = false;

  constructor() { }

  ngOnInit(): void {

  }

  onChangeToggle() {
    this.setDark = !this.setDark;
    this.mode.emit(this.setDark);
    console.log(this.setDark);
  }

}

Then in the app.comoonent.html receive boolean

 <app-header (mode)="receiveMode($event)"></app-header>

  <router-outlet></router-outlet>



// app.component.ts


import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {

  setMode = false;

  receiveMode($event) {
    this.setMode = $event;
    console.log("MODEEEE", this.setMode);
  }



  title = 'about-me';
} 

I have tried to wrap the div around the app-header and router-outlet like so:

<app-header (mode)="receiveMode($event)"></app-header>
<div class="darkTheme">
  <router-outlet></router-outlet>

and using ngClass:

<div [ngClass]="{
  darkTheme: setMode
}">
</div>

But it doesn't work. I did check to see whether or not the boolean is being logged into the console when toggling the switch. It is.

Answer 1

Have a look at this stackblitz: https://stackblitz.com/edit/angular-rubaka?file=src/app/toolbar-multirow-example.html

it toggles the class "dark-theme" on the #container:ElementRef:

<div #container style="padding: 4rem;" class="mat-typography dark-theme">

The styles.scss defines two different theme's on line 28 (default theme)...

// Include the default theme styles.
@include angular-material-theme($candy-app-theme);

and on line 39 (dark theme)...

.dark-theme {
  @include angular-material-theme($dark-theme)
};

Hope this helps.