kickin_utilities

A Flutter package of common utilities: constants, extensions, helpers, and mixins. No dependencies beyond Flutter itself.

Part of the Kickin toolkit for Flutter.

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Installation

flutter pub add kickin_utilities

Or add it manually to your pubspec.yaml:

dependencies:
  kickin_utilities: ^0.0.1+1

Then import it:

import 'package:kickin_utilities/kickin_utilities.dart';

---

What's included

Feature	What it gives you
Constants	Spacing tokens (KSpacing) and motion curves (KCurves)
Extensions	Shortcuts on String, num, Color, BuildContext, Duration, and Riverpod providers
Helpers	KResult for safe async operations, KIsolate for background tasks
Mixins	Scroll offset tracking, scroll threshold detection, and page controller ownership

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Constants

KSpacing

Named spacing tokens for consistent layout padding and gaps.

Container(padding: const EdgeInsets.all(KSpacing.md));

Available sizes: xxs, xs, sm, md, lg, xl, xxl, xxxl, huge, massive

KCurves

Pre-defined animation curves for consistent motion across your app.

// Spring curves
KCurves.instantSpring
KCurves.defaultIosSpring
KCurves.bouncySpring
KCurves.snappySpring
KCurves.interactiveSpring

// Easing curves
KCurves.fastInSlowOut
KCurves.easeOutSine
KCurves.easeOutCirc
KCurves.bounceOut

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Extensions

On num

Duration helpers and spacing widgets:

await 500.inMs.delay();   // wait 500 ms
await 2.inSeconds.delay();

16.toVBox    // SizedBox(height: 16)
16.toHBox    // SizedBox(width: 16)
16.toVSliverBox  // sliver version
16.toHSliverBox  // sliver version

On BuildContext

Theme and layout shortcuts — no more deep MediaQuery.of(context) chains:

context.isDarkMode
context.theme
context.scaffoldBackgroundColor
context.screenSize
context.deviceWidth
context.deviceHeight
context.topPadding
context.bottomPadding
context.viewInsets

On String

final data = '{"name":"Alice"}'.decodeJson; // Map or list

On Color

final lighter = myColor.lightenColor(); // HSL-based lightening

On Duration

await 1.inSeconds.delay(); // Future.delayed shorthand

On Riverpod providers

Shortcuts on ProviderListenable, Ref, WidgetRef, and notifier providers:

// Read or watch a provider
userProvider.read(ref)
userProvider.watch(ref)

// Boolean inversion
userProvider.not(ref)       // reads the negation
userProvider.watchNot(ref)  // watches the negation

// Keep alive for a duration then auto-dispose
ref.keepAliveFor(const Duration(minutes: 5));

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Helpers

KResult<T> — safe async operations

A wrapper for loading, success, and error states. Use it instead of repeating try/catch everywhere.

final result = await KResult.tryRunAsync(() async => fetchUser(id));

if (result.isSuccess) {
  print(result.value);
} else {
  print(result.message); // readable error
}

Constructors:

Method	Description
KResult.loading()	Represents an in-progress state
KResult.success(value)	Wraps a successful result
KResult.error(message)	Wraps an error with a message
KResult.tryRunAsync(fn)	Runs async work, captures errors automatically
KResult.tryRun(fn)	Same but synchronous

Chaining:

final result = await KResult.tryRunAsync(() => fetchUser(id))
    .then((r) => r.doNext(() => fetchPosts(r.value!.id)))
    .onError((r) => print('Failed: ${r.message}'));

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KIsolate — background tasks

Run CPU-heavy work off the main thread without managing isolates manually.

KIsolate — one-shot task

final result = await KIsolate.run(
  arg: largeDataSet,
  task: (data) => processList(data),
);

KIsolateContinuous — persistent worker

Runs sequential tasks in a single long-lived isolate. Good for queued background work like file processing.

final worker = KIsolateContinuous<String, String>();
await worker.spawn(task: (input) => compressString(input));
final output = await worker.run(arg: 'some large text');

KIsolateAccess mixin

Add isolate helpers directly to a class:

class MyService with KIsolateAccess {
  Future<String> process(String input) => isolateRun(arg: input, task: heavyFn);
}

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Mixins

Drop-in state helpers for common widget patterns.

KScrollOffsetNotifierMixin

Exposes the current scroll offset as a ValueNotifier<double>. Automatically updates as the user scrolls.

class _MyState extends State<MyWidget> with KScrollOffsetNotifierMixin {
  @override
  Widget build(BuildContext context) {
    return ValueListenableBuilder(
      valueListenable: scrollOffset,
      builder: (_, offset, __) => Text('Offset: $offset'),
    );
  }
}

KIsScrolledNotifierMixin

Flips a ValueNotifier<bool> when scroll passes the toolbar-height threshold. Useful for showing/hiding app bar shadows or sticky headers.

KPageControllerMixin

Owns and disposes a PageController for you — no boilerplate initState/dispose needed.

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Full example

import 'package:kickin_utilities/kickin_utilities.dart';

Future<void> main() async {
  // Safe async operation
  final result = await KResult.tryRunAsync(() async {
    await 1.inSeconds.delay();
    return '{"name":"Alice"}'.decodeJson;
  });

  if (result.isSuccess) {
    print(result.value); // {name: Alice}
  } else {
    print(result.message);
  }
}

// Spacing in widgets
Widget spacedColumn() => Column(
  children: [
    const Text('Hello'),
    16.toVBox,
    const Text('World'),
  ],
);

// Context shortcuts
Widget header(BuildContext context) => Container(
  width: context.deviceWidth,
  padding: EdgeInsets.only(top: context.topPadding),
  color: context.isDarkMode ? Colors.black : Colors.white,
);

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API reference summary

Class / Extension	Purpose
KSpacing	Named spacing constants
KCurves	Named animation curves
KResult<T>	Safe async result wrapper
KIsolate	One-shot background isolate task
KIsolateContinuous	Persistent background worker isolate
KIsolateAccess	Mixin for easy isolate access in any class
KIsolateException	Exception thrown when isolate work fails
KScrollOffsetNotifierMixin	Tracks scroll offset in a ValueNotifier
KIsScrolledNotifierMixin	Detects when scroll passes a threshold
KPageControllerMixin	Owns and disposes a PageController