flutter assertion_error ai_generated true

Assertion failed: 'verticalDirection' is null or not set

ID: flutter/assertion-failed-vertical-viewport

Also available as: JSON · Markdown · 中文

93%Fix Rate

87%Confidence

1Evidence

2023-09-01First Seen

Version Compatibility

Version	Status	Introduced	Deprecated	Notes
Flutter 3.13	active	—	—	—
Flutter 3.16	active	—	—	—
Flutter 3.19	active	—	—	—

Root Cause

A vertical viewport (e.g., ListView, Column) is used without specifying a constrained height, causing infinite vertical space.

generic

中文

垂直视口（例如 ListView、Column）在没有指定约束高度的情况下使用，导致无限垂直空间。

Official Documentation

https://api.flutter.dev/flutter/widgets/ScrollView-class.html

Workarounds

95% success Wrap the ListView in a Container or SizedBox with a fixed height: SizedBox( height: 300, child: ListView( children: [...], ), )
```
Wrap the ListView in a Container or SizedBox with a fixed height:
SizedBox(
  height: 300,
  child: ListView(
    children: [...],
  ),
)
```
90% success If inside a Column, wrap the ListView in an Expanded and ensure the Column has a bounded height (e.g., by wrapping the Column in a SizedBox or Expanded): Column( children: [ Expanded( child: ListView(children: [...]), ), ], )
```
If inside a Column, wrap the ListView in an Expanded and ensure the Column has a bounded height (e.g., by wrapping the Column in a SizedBox or Expanded):
Column(
  children: [
    Expanded(
      child: ListView(children: [...]),
    ),
  ],
)
```
85% success Use a CustomScrollView with slivers if you need mixed scrolling and non-scrolling content.
```
Use a CustomScrollView with slivers if you need mixed scrolling and non-scrolling content.
```

中文步骤

Wrap the ListView in a Container or SizedBox with a fixed height:
SizedBox(
  height: 300,
  child: ListView(
    children: [...],
  ),
)

If inside a Column, wrap the ListView in an Expanded and ensure the Column has a bounded height (e.g., by wrapping the Column in a SizedBox or Expanded):
Column(
  children: [
    Expanded(
      child: ListView(children: [...]),
    ),
  ],
)

Use a CustomScrollView with slivers if you need mixed scrolling and non-scrolling content.

Dead Ends

Common approaches that don't work:

Wrapping the ListView in an Expanded widget inside a Column 40% fail
Expanded only works when the parent has a fixed height; if the Column itself is unbounded, it still fails.
Setting shrinkWrap: true on the ListView without also constraining the parent 30% fail
ShrinkWrap only affects the viewport's own size calculation; the parent widget must still provide a finite height constraint.
Using Flexible instead of Expanded 50% fail
Flexible also requires a bounded parent; same fundamental issue.