How to give class name to animation state in angular 2/4?

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06-10-2024

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Adding Class Names to Animation States in Angular (2/4+)

Animations in Angular are a powerful tool for enhancing user experience. However, adding dynamic styling based on animation states can sometimes feel like a challenge. This article will guide you through the process of applying class names to animation states in Angular 2 and above, allowing you to create truly dynamic and engaging UI experiences.

The Problem:

You want to apply specific CSS styles to your element based on its animation state (e.g., "start", "end", "active"). You need a way to associate a class name with these animation states so you can target them with CSS.

Let's Illustrate:

Imagine you have a simple "fade-in" animation for a welcome message. You want to apply a "hidden" class to the message before the animation starts and a "visible" class once the animation completes.

import { trigger, style, animate, transition } from '@angular/animations';

@Component({
  selector: 'app-welcome',
  template: `
    <div [@fadeIn]="isVisible">
      Welcome!
    </div>
  `,
  animations: [
    trigger('fadeIn', [
      transition(':enter', [
        style({ opacity: 0 }),
        animate('500ms ease-in', style({ opacity: 1 }))
      ])
    ])
  ]
})
export class WelcomeComponent {
  isVisible = true;
}

The Solution:

The key lies in utilizing the state() function in your animation trigger. state() allows you to define the styles for a specific state and, more importantly, to associate a class name with that state.

Enhanced Code:

import { trigger, state, style, animate, transition } from '@angular/animations';

@Component({
  selector: 'app-welcome',
  template: `
    <div [@fadeIn]="isVisible" class="message">
      Welcome!
    </div>
  `,
  animations: [
    trigger('fadeIn', [
      state('hidden', style({ opacity: 0, className: 'hidden' })), // Add className
      state('visible', style({ opacity: 1, className: 'visible' })), // Add className
      transition(':enter', [
        style({ opacity: 0 }),
        animate('500ms ease-in', style({ opacity: 1 }))
      ])
    ])
  ]
})
export class WelcomeComponent {
  isVisible = true;
}

Explanation:

1. state() Function: We use state() to define the styles for two distinct states, "hidden" and "visible."
2. className: The className property within the state() function is where the magic happens. We assign the desired class names ("hidden" and "visible") to the respective animation states.
3. @fadeIn binding: The @fadeIn binding on the <div> element associates the animation with our component's isVisible property, ensuring the correct state is applied.

CSS Styles:

.message.hidden {
  /* Styles for hidden state */
  opacity: 0;
}

.message.visible {
  /* Styles for visible state */
  opacity: 1;
}

Additional Insights:

• You can apply multiple class names to a state by separating them with spaces (e.g., className: 'hidden fade-out').
• You can utilize the class property within the style() function to conditionally add and remove classes during animation.

Benefits of Using Class Names:

• Fine-grained Control: You have complete control over the styling of each animation state.
• Dynamic Styling: Easily adjust styles based on the animation state.
• CSS Reusability: Apply the same classes for other elements that need similar styling.

Conclusion:

By incorporating the state() function with the className property, you can seamlessly integrate animation states with CSS classes to create dynamic and visually captivating user interfaces in Angular. This approach offers flexibility and control over your animations, allowing you to bring your web application to life.