Slivers & Advanced Scrolling — Flutter Course

What you'll learn

Compose sophisticated scrolling experiences with slivers, persistent headers, collapsing regions, restoration, and measured performance. The lesson turns the APIs into a repeatable engineering workflow instead of a collection of isolated snippets.

By the end of this lesson, you'll be able to:

Apply Sliver protocol in a production-shaped Flutter feature
Apply CustomScrollView in a production-shaped Flutter feature
Apply SliverAppBar in a production-shaped Flutter feature
Apply Persistent headers in a production-shaped Flutter feature

Core mental model

Connect each API to the decision it supports. Flutter code stays maintainable when state, ownership, lifecycle, and platform boundaries are explicit.

Concept	What it means	Decision rule
Sliver	A scrollable-area fragment governed by the sliver protocol	Use to combine lazy lists, grids, headers, and fill regions in one scroll view
Pinned header	A header remains visible at the viewport edge	Reserve persistent space for high-value context or controls
Keep alive	A lazy child retains selected state offscreen	Preserve only expensive or user-entered state with clear ownership

Professional workflow

Work in small vertical slices and keep behavior observable from the first iteration.

Define the composed sliver catalog boundary: user goal, inputs, visible states, ownership, and expected failures.
Build the smallest working vertical slice with typed data and explicit dependencies.
Represent loading, empty, success, and failure behavior where the feature can encounter them.
Verify logic away from the UI, then exercise the rendered behavior at its public boundary.
Inspect lifecycle, accessibility, performance, security, and platform behavior before widening the feature.
Refactor only after behavior is protected by repeatable evidence.

Protect the frame

Keep build methods predictable, move side effects to explicit owners, and measure before introducing caches, isolates, or architectural layers.

Guided Flutter lab

Build a focused composed sliver catalog slice

This compact example keeps the important ownership and data-flow decisions visible so the behavior is easy to extend and test.

lib/course_catalog.dart

CustomScrollView(
  restorationId: 'course-catalog',
  slivers: [
    const SliverAppBar(
      pinned: true,
      expandedHeight: 180,
      flexibleSpace: FlexibleSpaceBar(title: Text('Flutter course')),
    ),
    SliverPadding(
      padding: const EdgeInsets.all(16),
      sliver: SliverList.builder(
        itemCount: lessons.length,
        itemBuilder: (context, index) => LessonTile(lesson: lessons[index]),
      ),
    ),
  ],
)

Production practice

Contract

Define the composed sliver catalog inputs, outputs, owner, lifecycle, visible states, and platform assumptions before selecting APIs or packages.

Verification

Protect pure rules with unit tests and the rendered public contract with widget or integration evidence; include one unavailable or failure case.

Operations

Keep dependencies replaceable, log actionable context without user secrets, and measure user-visible behavior before optimizing.

Common failure mode

Nesting independent scroll views to combine sections creates gesture, sizing, restoration, and performance problems that one sliver composition avoids.

Independent workshop

Extend the guided lab into a review-ready composed sliver catalog feature that fits the running course portfolio app.

Your finished workshop must include:

Sliver protocol
CustomScrollView
SliverAppBar
Persistent headers
State retention
Automated verification and a short design note

Definition of done

Demonstrate the happy path, an empty or unavailable state, and at least one failure path. Add an automated check and a short note explaining one design decision.

Recap & quick check

Key takeaways

Sliver: Use to combine lazy lists, grids, headers, and fill regions in one scroll view
Pinned header: Reserve persistent space for high-value context or controls
Keep alive: Preserve only expensive or user-entered state with clear ownership

Quick check

1. Which rule best applies to Sliver?

2. Which rule best applies to Pinned header?

3. Which rule best applies to Keep alive?

Next: HTTP, REST & JSON