How to Use View Transition API in Angular for Partial Animations?

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Introduction


Animating your Angular application can greatly enhance user experience. Utilizing Web APIs like the View Transition API offers dynamic animations when transitioning between different states in your application. You specifically want to animate parts of your Angular application such as a sidebar menu, which requires integrating the View Transition API effectively.

Why Should You Use the View Transition API?


The View Transition API allows developers to create smooth transitions between different views in a web application. This helps to improve user engagement by providing visual feedback during state changes. In your scenario, you want to animate the transition when users select a food category to filter products. This partial animation enhances the user experience without overwhelming them with full-screen transitions.

Setting Up View Transition in Angular


To implement the View Transition API in your Angular application, you will need to make changes to your product-grid.component.ts and utilize document.startViewTransition(). Below are the steps to accomplish this.

Step 1: Modify the Component


You mentioned that your component looks like this:

filteredProducts$!: Observable<Product[]>;
selectedCategory$: Observable<any>;
private store = inject(Store<AppState>);

constructor() {
this.selectedCategory$ = this.store.select(
CategorySelectors.selectSelectedCategory
);
this.filteredProducts$ = combineLatest([
this.store.select(ProductSelectors.selectAllProducts),
this.store.select(CategorySelectors.selectSelectedCategoryId),
]).pipe(
map(([products, selectedCategoryId]) => {
if (selectedCategoryId) {
return products.filter((p) => p.categoryId === selectedCategoryId);
}
return products;
})
);
}

ngOnInit() {
this.store
.select(ProductSelectors.selectAllProducts)
.subscribe((products) => {
if (!products || products.length === 0) {
this.store.dispatch(ProductActions.loadProducts());
}
});
}


You can incorporate the View Transition API as follows:

selectCategory(categoryId: number) {
document.startViewTransition(() => {
this.store.dispatch(CategoryActions.selectCategory({ categoryId }));
// Any additional code for fetching filtered products
});
}

Step 2: Update the HTML File


In your sidebar category menu template, when a user clicks on a category, call the selectCategory() method, passing the selected category ID. Here’s how you can modify your HTML:

<mat-sidenav-container class="sidenav-container">
<mat-sidenav ...>
<app-category-menu (categorySelected)="selectCategory($event)">
</app-category-menu>
</mat-sidenav>

<mat-sidenav-content class="content-area">
<div class="main-content mat-rounded-medium">
<router-outlet></router-outlet>
</div>
</mat-sidenav-content>
</mat-sidenav-container>

Step 3: Define the Event Emitter in Category Menu


Ensure that the app-category-menu component emits the selected category. It can look like this:

@Output() categorySelected = new EventEmitter<number>();

selectCategory(categoryId: number) {
this.categorySelected.emit(categoryId);
}

Frequently Asked Questions


1. What browsers support the View Transition API?
The View Transition API is relatively new and is supported in modern browsers. Check the

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for the latest compatibility information.

2. Can this API be used for full-screen transitions?
, though your focus is on partial animations. The API can be leveraged for more extensive transitions too.

3. How does this API affect performance?
Using the View Transition API can improve perceived performance by providing smooth transitions that are more visually appealing, but you should always profile your application if performance concerns arise.

Conclusion


Integrating the View Transition API into your Angular application allows you to create beautiful and responsive transitions that improve user engagement. By modifying your components to utilize document.startViewTransition(), you can provide specific animations for parts of your app, like category filtering in a product grid. This not only makes your application visually appealing but also creates a seamless user experience, keeping your users engaged and happy.

If you want a smoother interface for your Angular application, experimenting with the View Transition API is an excellent step forward.

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