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Type: SignalAnimatedBuilder

API reference and details for SignalAnimatedBuilder from signals.dart.

SignalAnimatedBuilder#

Kind: class  |  Package: package:signals_flutter

Class: SignalAnimatedBuilder#

A reactive builder widget designed for performance optimizations using child caching.

SignalAnimatedBuilder is the modern, drop-in replacement for Flutter's native AnimatedBuilder or the deprecated WatchBuilder.

When you have a complex or computationally heavy widget subtree that does not depend on any signal values, you should pass it as the child parameter. This subtree is cached and is never rebuilt when the signals mutate, delivering a massive rendering boost.

Performance Optimization Example# 

final count = signal(0);

class OptimizedCounter extends StatelessWidget {
  const OptimizedCounter({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SignalAnimatedBuilder(
        // 1. Define the heavy subtree once. It will be cached:
        child: const HeavyComplexSubtreeWidget(),

        // 2. The builder receives the cached child:
        builder: (context, cachedChild) {
          return Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Text('Dynamic Count: ${count.value}'),
              const SizedBox(height: 20),
              // 3. Render the cached child directly:
              cachedChild!,
            ],
          );
        },
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () => count.value++,
        child: const Icon(Icons.add),
      ),
    );
  }
}

Tip

Always use SignalAnimatedBuilder when rendering dynamic signal values alongside static, heavy subtrees. This minimizes CPU cycles and avoids rebuilding static layouts on frame updates.

Members of SignalAnimatedBuilder#

Member Type Signature Description
SignalAnimatedBuilder constructor dart SignalAnimatedBuilder({super.key, required this.builder, this.child, this.debugLabel, this.dependencies = const []}) Creates a SignalAnimatedBuilder widget.
builder field dart Widget Function(BuildContext context, Widget? child) builder The widget to rebuild when any signals change.
child field dart Widget? child Optional pre-built child subtree that does not rebuild.
debugLabel field dart String? debugLabel Optional debug label to use for devtools.
dependencies field dart List<core.ReadonlySignal> dependencies List of optional dependencies to watch.
build method dart Widget build(BuildContext context)

References#

The SignalAnimatedBuilder type is referenced and used in the following pages: