AppBar theme color parameter deprecation

The color parameter in AppBarTheme and AppBarThemeData constructors and their copyWith methods hasve been deprecated. Use backgroundColor instead. This change affects how AppBar themes are configured and might cause deprecation warnings in existing code.

The AppBar theming system had two parameters that controlled the same property: color and backgroundColor. This duplication created confusion and inconsistency in the API. To improve clarity and consistency, the color parameter has been deprecated in favor of backgroundColor.

The deprecation affects the following classes and methods:

• AppBarTheme constructor
• AppBarTheme.copyWith method
• AppBarThemeData constructor
• AppBarThemeData.copyWith method

When using the deprecated color parameter, you'll see warnings like:

'color' is deprecated and shouldn't be used. Use backgroundColor instead.
This feature was deprecated after v3.33.0-0.2.pre.

The classes also include assertion checks to prevent using both parameters simultaneously:

The color and backgroundColor parameters mean the same thing. Only specify one.

Replace all uses of the color parameter with backgroundColor in AppBarTheme and AppBarThemeData constructors and copyWith methods.

Code before migration:

// AppBarTheme constructor
AppBarTheme(
  color: Colors.blue,
  elevation: 4.0,
)

// AppBarTheme copyWith
theme.copyWith(
  color: Colors.red,
  elevation: 2.0,
)

// AppBarThemeData constructor
AppBarThemeData(
  color: Colors.green,
  elevation: 4.0,
)

// AppBarThemeData copyWith
themeData.copyWith(
  color: Colors.purple,
  elevation: 2.0,
)

Code after migration:

// AppBarTheme constructor
AppBarTheme(
  backgroundColor: Colors.blue,
  elevation: 4.0,
)

// AppBarTheme copyWith
theme.copyWith(
  backgroundColor: Colors.red,
  elevation: 2.0,
)

// AppBarThemeData constructor
AppBarThemeData(
  backgroundColor: Colors.green,
  elevation: 4.0,
)

// AppBarThemeData copyWith
themeData.copyWith(
  backgroundColor: Colors.purple,
  elevation: 2.0,
)

Landed in version: 3.33.0-0.2.pre
In stable release: 3.35.4

API documentation:

• AppBarTheme
• AppBarThemeData

Relevant PRs:

• AppBar theme color parameter deprecation #170624