Flutter › Flutter Performance Optimization
How does using ListView.builder instead of manually constructing a plain ListView with a fully complete, fixed list of children genuinely improve performance specifically for a very long scrollable list?
IntermediateAnswer
ListView.builder uses what is generally referred to as lazy building, meaning it only actually constructs the specific individual list item widgets that are genuinely currently visible on screen, plus a small reasonable additional buffer just beyond the current visible edges, rather than the considerably less efficient plain ListView approach, which instead eagerly constructs every single individual item within the entire list all together immediately upfront regardless of whether they are actually currently visible on screen at all, and for a genuinely very long list containing potentially hundreds or even thousands of individual items, this specific lazy building difference in approach can result in a truly dramatic, easily measurable overall performance improvement.
ListView.builder(
itemCount: products.length,
itemBuilder: (context, index) => ProductTile(product: products[index]),
)Real-world example A product catalog app switches from a plain ListView containing several thousand individual eagerly constructed items over to properly using ListView.builder instead, dramatically and easily measurably reducing both the app's own initial screen load time and its overall ongoing memory usage.