Chapter 2 · Practice 3 of 5

Use `const` constructors wherever you can

Why it matters

The Flutter docs say to use const constructors on widgets as much as possible, since they allow Flutter to short-circuit most of the rebuild work. A const widget is created once at compile time and reused, so when its parent rebuilds, Flutter can skip it.

Give your own widgets a const constructor when all their fields are final.
Add const at call sites: const SizedBox(height: 16), const Icon(Icons.add).
Let the lints from flutter_lints point out the places you missed.

This is one of the few performance tips that costs nothing and has no downside.

Declare const constructors on widgets with only final fields
Accept the analyzer's "prefer const" fixes in bulk

Avoid

Adding a non-final field to a widget just to mutate it later

Example

Dart

class SectionTitle extends StatelessWidget {
  const SectionTitle(this.text, {super.key});
  final String text;

  @override
  Widget build(BuildContext context) =>
      Text(text, style: Theme.of(context).textTheme.titleMedium);
}

// At the call site
const SectionTitle('Recent orders');