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BreakingHigh impactOfficial migration guidesince 3.32.0landed 3.31.0-0.0.pre

Material Theme System Updates

Framework · Official source

What changed?

`CardTheme`, `DialogTheme` and `TabBarTheme` were refactored to conform to Flutter's conventions for component themes. `CardThemeData`, `DialogThemeData` and `TabBarThemeData` were added to define overrides for the defaults of the component visual properties.

Will this affect my application?

Who is affected
Applications and packages relying on the previous behaviour or signature. Code that uses CardTheme, DialogTheme, TabBarTheme and related APIs.
Practical impact
Behaviour or API differences that can break builds or change runtime behaviour.
What action should I take?
Follow the official migration guide below, update affected call sites, run `dart fix --apply` where a fix is available, then run your tests.
APIs mentioned:CardThemeDialogThemeTabBarThemeCardThemeDataDialogThemeDataTabBarThemeDataThemeData.cardThemeThemeDataThemeData.dialogThemeThemeData.tabBarTheme

How do I migrate safely?

Before and after (from the official guide)

dart+3−3
Before
1 final ThemeData theme = ThemeData(
2− cardTheme: CardTheme(),
3− dialogTheme: DialogTheme(),
4− tabBarTheme: TabBarTheme(),
5 );
After
1 final ThemeData theme = ThemeData(
2+ cardTheme: CardThemeData(),
3+ dialogTheme: DialogThemeData(),
4+ tabBarTheme: TabBarThemeData(),
5 );
Raw before / after
final ThemeData theme = ThemeData(
    cardTheme: CardTheme(),
    dialogTheme: DialogTheme(),
    tabBarTheme: TabBarTheme(),
);
final ThemeData theme = ThemeData(
    cardTheme: CardThemeData(),
    dialogTheme: DialogThemeData(),
    tabBarTheme: TabBarThemeData(),
);
Official migration guide (excerpt, © The Flutter Authors, CC BY 3.0)

Previously, the type of ThemeData.cardTheme was Object? to accept both CardTheme and CardThemeData. Now that the type has been changed to CardThemeData?, a migration is required if ThemeData.cardTheme is used. Similarly, the types of ThemeData.dialogTheme and ThemeData.tabBarTheme should be migrated to DialogThemeData and TabBarThemeData, respectively.

Code before migration:

final ThemeData theme = ThemeData(
    cardTheme: CardTheme(),
    dialogTheme: DialogTheme(),
    tabBarTheme: TabBarTheme(),
);

Code after migration:

final ThemeData theme = ThemeData(
    cardTheme: CardThemeData(),
    dialogTheme: DialogThemeData(),
    tabBarTheme: TabBarThemeData(),
);
Migration assistantAI-generated · grounded in cited sources
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Evidence & verification

Official migration guide·Verified classification (95%)

Listed in the official breaking-changes index (docs.flutter.dev/release/breaking-changes).

An official announcement or migration guide documents an intended behaviour or API change. A verified source change (git diff) shows code changed but does not by itself prove a public API is breaking. AI interpretations are labelled and never used to classify a change.

Source commit
b3045439b7c0
Source last updated
Oct 21, 2026
Last synchronized
Oct 21, 2026
Publication status
published
Publication history
  • Oct 21, 2026, 8:31 PM: new → published (ingestion) — Backed by an official breaking-change/migration guide.
AI explanationAI-generated · grounded in cited sources
AI explanations are not configured
Set AI_PROVIDER (for example to openai-compatible with a local Ollama or LM Studio endpoint) to enable grounded explanations. Everything else on this page works without an AI provider.
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