WidgetStateProperty class - widgets library (original) (raw)

Interface for classes that resolve to a value of type T based on a widget's interactive "state", which is defined as a set of WidgetStates.

Widget state properties represent values that depend on a widget's "state". The state is encoded as a set of WidgetState values, likeWidgetState.focused, WidgetState.hovered, WidgetState.pressed. For example the InkWell.overlayColor defines the color that fills the ink well when it's pressed (the "splash color"), focused, or hovered. The InkWelluses the overlay color's resolve method to compute the color for the ink well's current state.

ButtonStyle, which is used to configure the appearance of buttons like TextButton, ElevatedButton, and OutlinedButton, has many material state properties. The button widgets keep track of their current material state and resolve the button style's material state properties when their value is needed.

This example shows how the default text and icon color (the "foreground color") of a TextButton can be overridden with aWidgetStateProperty. In this example, the button's text color will be colored differently depending on whether the button is pressed, hovered, or focused.

link

To create a local project with this code sample, run:
flutter create --sample=widgets.WidgetStateProperty.1 mysample

Performance Consideration

In order for constructed WidgetStateProperty objects to be recognized as equivalent, they need to either be const objects, or have overrides foroperator== and hashCode.

This comes into play when, for instance, two ThemeData objects are being compared for equality.

For a concrete WidgetStateProperty object that supports stable equality checks, consider using WidgetStateMapper.

See also:

• MaterialStateProperty, the Material specific version ofWidgetStateProperty.
• WidgetStateColor, a Color that implements WidgetStateProperty which is used in APIs that need to accept either a Color or aWidgetStateProperty<Color>.
• WidgetStateMouseCursor, a MouseCursor that implementsWidgetStateProperty which is used in APIs that need to accept either a MouseCursor or a WidgetStateProperty.
• WidgetStateOutlinedBorder, an OutlinedBorder that implementsWidgetStateProperty which is used in APIs that need to accept either an OutlinedBorder or a WidgetStateProperty.
• WidgetStateBorderSide, a BorderSide that implementsWidgetStateProperty which is used in APIs that need to accept either a BorderSide or a WidgetStateProperty.
• WidgetStateTextStyle, a TextStyle that implementsWidgetStateProperty which is used in APIs that need to accept either a TextStyle or a WidgetStateProperty.

Implementers

• MaterialStateOutlineInputBorder
• MaterialStateUnderlineInputBorder
• WidgetStateBorderSide
• WidgetStateColor
• WidgetStateInputBorder
• WidgetStateMapper
• WidgetStateMouseCursor
• WidgetStateOutlinedBorder
• WidgetStatePropertyAll
• WidgetStateTextStyle

Constructors

WidgetStateProperty()

This abstract constructor allows extending the class.

WidgetStateProperty.fromMap(WidgetStateMap<T> map)

Creates a property that resolves using a WidgetStateMap.

const

factory

Properties

hashCode → int

The hash code for this object.

no setterinherited

runtimeType → Type

A representation of the runtime type of the object.

no setterinherited

Methods

noSuchMethod(Invocation invocation)→ dynamic

Invoked when a nonexistent method or property is accessed.

inherited

resolve(Set<WidgetState> states)→ T

Returns a value of type T that depends on states.

toString()→ String

A string representation of this object.

inherited

Operators

operator ==(Object other)→ bool

The equality operator.

inherited

Static Methods

all<T>(T value)→ WidgetStateProperty<T>

Convenience method for creating a WidgetStateProperty that resolves to a single value for all states.

lerp<T>(WidgetStateProperty<T>? a, WidgetStateProperty<T>? b, double t, T? lerpFunction(T?, T?, double))→ WidgetStateProperty<T?>?

Linearly interpolate between two WidgetStatePropertys.

resolveAs<T>(T value, Set<WidgetState> states)→ T

Resolves the value for the given set of states if value is aWidgetStateProperty, otherwise returns the value itself.

resolveWith<T>(WidgetPropertyResolver<T> callback)→ WidgetStateProperty<T>

Convenience method for creating a WidgetStateProperty from aWidgetPropertyResolver function alone.