# Flutter Errors

Use when hitting layout errors (RenderFlex overflow, unbounded constraints, RenderBox...

- Repository: https://github.com/evanca/flutter-ai-rules (668 stars)
- Category: Engineering
- License: MIT
- Last updated: 2026-10-30
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add evanca/flutter-ai-rules --skill flutter-errors -g -a claude-code -y`
Codex: `npx skills add evanca/flutter-ai-rules --skill flutter-errors -g -a codex -y`
Cursor: `npx skills add evanca/flutter-ai-rules --skill flutter-errors -g -a cursor -y`
Gemini CLI: `npx skills add evanca/flutter-ai-rules --skill flutter-errors -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add evanca/flutter-ai-rules`

## Description

Use when hitting layout errors (RenderFlex overflow, unbounded constraints, RenderBox not laid out), scroll errors, or setState-during-build errors.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Flutter Errors Skill

This skill provides solutions for the most common Flutter runtime and layout errors.

---

## RenderFlex Overflowed

**Error:** `A RenderFlex overflowed by X pixels on the right/bottom.`

**Cause:** A `Row` or `Column` contains children that are wider/taller than the available space.

**Fix:** Wrap the overflowing child in `Flexible` or `Expanded`, or constrain its size:

```dart
Row(
  children: [
    Expanded(child: Text('Long text that might overflow')),
    Icon(Icons.info),
  ],
)
```

---

## Vertical Viewport Given Unbounded Height

**Error:** `Vertical viewport was given unbounded height.`

**Cause:** A `ListView` (or other scrollable) is placed inside a `Column` without a bounded height.

**Fix:** Wrap the `ListView` in `Expanded` or give it a fixed height with `SizedBox`:

```dart
Column(
  children: [
    Text('Header'),
    Expanded(
      child: ListView(children: [...]),
    ),
  ],
)
```

---

## InputDecorator Cannot Have Unbounded Width

**Error:** `An InputDecorator...cannot have an unbounded width.`

**Cause:** A `TextField` or similar widget is placed in a context without width constraints.

**Fix:** Wrap it in `Expanded`, `SizedBox`, or any parent that provides width constraints:

```dart
Row(
  children: [
    Expanded(child: TextField()),
  ],
)
```

---

## setState Called During Build

**Error:** `setState() or markNeedsBuild() called during build.`

**Cause:** `setState` or `showDialog` is called directly inside the `build` method.

**Fix:** Trigger state changes in response to user actions, or defer to after the frame using `addPostFrameCallback`:

```dart
@override
void initState() {
  super.initState();
  WidgetsBinding.instance.addPostFrameCallback((_) {
    // Safe to call setState or showDialog here
  });
}
```

---

## ScrollController Attached to Multiple Scroll Views

**Error:** `The ScrollController is attached to multiple scroll views.`

The rest: https://github.com/evanca/flutter-ai-rules/blob/HEAD/skills/flutter-errors/SKILL.md