cdk-virtual-scroll-viewport usage with angular/flex-layout (row and wrap)

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06-10-2024

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Mastering Angular Virtual Scrolling with cdk-virtual-scroll-viewport and flex-layout

Angular's cdk-virtual-scroll-viewport is a powerful tool for rendering large lists efficiently, but managing layout within the viewport can be tricky. This article delves into the intricacies of integrating cdk-virtual-scroll-viewport with flex-layout for achieving flexible row and wrap layouts.

The Challenge:

Imagine you need to display a massive collection of items in a grid-like fashion. Traditional approaches would render all elements at once, leading to performance bottlenecks. Enter cdk-virtual-scroll-viewport, which intelligently renders only the visible items, drastically improving performance. However, integrating flex-layout for dynamic row and wrap behavior within the viewport requires careful consideration.

Scenario:

Let's assume you're building a product listing page where you want to display hundreds of products in a responsive grid that adapts to different screen sizes.

Original Code:

<cdk-virtual-scroll-viewport itemSize="100" (scrolledIndexChange)="onScrolledIndexChange($event)">
  <div *cdkVirtualFor="let product of products" class="product-item">
    <!-- Product details -->
  </div>
</cdk-virtual-scroll-viewport>

This code snippet uses cdk-virtual-scroll-viewport to render only the visible products. However, it lacks any layout structure. Let's introduce flex-layout to create our grid layout:

<cdk-virtual-scroll-viewport itemSize="100" (scrolledIndexChange)="onScrolledIndexChange($event)">
  <div fxLayout="row wrap" fxLayoutGap="10px">
    <div *cdkVirtualFor="let product of products" class="product-item" fxFlex="0 0 25%">
      <!-- Product details -->
    </div>
  </div>
</cdk-virtual-scroll-viewport>

This modified code utilizes fxLayout="row wrap" to wrap the products into rows and fxFlex="0 0 25%" to distribute them equally in a 4-column grid.

Insights and Best Practices:

• Understanding itemSize: The itemSize attribute is crucial for virtual scrolling to work correctly. It defines the height of each item in pixels, allowing the viewport to calculate the visible range.
• fxLayoutGap: fxLayoutGap provides consistent spacing between items, enhancing visual appeal.
• fxFlex: The fxFlex directive is the cornerstone of flex-layout. By setting fxFlex="0 0 25%", we specify that each item should occupy 25% of the available width, resulting in a 4-column grid.
• Responsive Grid: The row wrap layout automatically adjusts to different screen sizes, ensuring a seamless user experience.
• Dynamic Content: You can further customize the grid layout by adjusting the fxFlex value based on screen size or data content. Use fxFlex.xs for extra small screens, fxFlex.sm for small screens, and so on.

Example:

<cdk-virtual-scroll-viewport itemSize="100" (scrolledIndexChange)="onScrolledIndexChange($event)">
  <div fxLayout="row wrap" fxLayoutGap="10px">
    <div *cdkVirtualFor="let product of products" class="product-item"
      [fxFlex]="product.isFeatured ? '0 0 50%' : '0 0 25%'"
    >
      <!-- Product details -->
    </div>
  </div>
</cdk-virtual-scroll-viewport>

This example demonstrates how fxFlex can be used dynamically to showcase featured products with a larger layout than regular products.

Conclusion:

Mastering the integration of cdk-virtual-scroll-viewport and flex-layout unlocks the potential for building highly performant and visually appealing interfaces. By leveraging these powerful tools, you can efficiently manage large data sets while maintaining a responsive and user-friendly layout.

References:

• Angular Material Virtual Scrolling
• Angular Flex Layout

Additional Value:

• Consider using @angular/cdk/scrolling for advanced scrolling features like smooth scrolling and custom scrollbars.
• Experiment with fxFlex and fxLayoutAlign for creating complex and dynamic layouts within your virtual scroll viewport.