How do layouts work in Flutter?

Question

Accepted Answer

Flutter builds layouts by **composing layout widgets** — like **Row**, **Column**, **Container**, **Stack**, and others — that arrange their children. Understanding these layout widgets and how they combine is fundamental to creating UI structures.

## Core layout widgets

```text
ROW → arrange children HORIZONTALLY (left to right)
COLUMN → arrange children VERTICALLY (top to bottom)
CONTAINER → a box: padding, margin, size, color, decoration, alignment (very common)
STACK → overlay children on top of each other (z-axis, positioned)
PADDING → add space around a child
CENTER → center a child
EXPANDED / FLEXIBLE → make children fill available space (in a Row/Column)
SizedBox → fixed-size box / spacing
ListView → scrollable list of children
```

## Composing a layout

```dart
Column(                          // vertical arrangement
  crossAxisAlignment: CrossAxisAlignment.start,
  children: [
    Text('Title'),
    SizedBox(height: 8),         // spacing
    Row(                         // horizontal arrangement
      children: [
        Icon(Icons.star),
        Expanded(                // takes remaining horizontal space
          child: Text('Description'),
        ),
      ],
    ),
    Container(                   // a styled box
      padding: EdgeInsets.all(16),
      color: Colors.blue,
      child: Text('Boxed'),
    ),
  ],
)
```

## Flexible layouts (Row/Column main and cross axes)

```text
→ MAIN axis (Row=horizontal, Column=vertical): mainAxisAlignment positions children
  along it (start, center, end, spaceBetween, etc.)
→ CROSS axis (perpendicular): crossAxisAlignment
→ EXPANDED/FLEXIBLE → children share available space proportionally (responsive layouts)
→ Compose these for flexible, responsive UIs.
```

## Why it matters

Understanding how layouts work in Flutter is fundamental because **arranging UI elements is essential to building any interface**, so it's must-know practical knowledge for Flutter development.

Flutter builds layouts by **composing layout widgets** — and understanding the **core layout widgets** (Row for horizontal arrangement, Column for vertical, Container for styled boxes with padding/margin/decoration, Stack for overlaying, Padding and Center for positioning, Expanded/Flexible for filling space, ListView for scrollable lists) is necessary to construct any UI structure.

These widgets are used constantly in every Flutter app.

Understanding how to **compose them** (nesting rows, columns, containers, and others to build complex layouts from simple pieces) is the fundamental practice of building Flutter UIs — the same composition principle that underlies all of Flutter, applied to layout.

Understanding the **flexible layout model** — the **main and cross axes** of Rows and Columns (mainAxisAlignment and crossAxisAlignment for positioning children) and **Expanded/Flexible** for sharing available space proportionally (enabling responsive layouts that adapt to different screen sizes) — is important for creating layouts that look good across devices, a key concern for mobile apps.

Since building any Flutter interface requires arranging elements with layout widgets, and since understanding the core layout widgets, how to compose them, and the flexible/responsive layout model is essential to constructing UIs, understanding how layouts work in Flutter is essential, foundational practical knowledge — a core skill used in every Flutter screen, necessary for translating designs into working, responsive interfaces, and fundamental to day-to-day Flutter development.