Ekhlass/Flutter_Documentation · Datasets at Hugging Face

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will eventually be deprecated according to
Flutter’s deprecation policy.For most Flutter widgets, upgrading to Material 3
is seamless. But some widgets couldn’t be
updated—entirely new implementations were needed,
such as NavigationBar.
You must make these changes to your code manually.
Until your app is entirely updated,
the UI might look or act a bit strange.
You can find the entirely new Material components by
visiting the Affected widgets page.Explore the updated components, typography, color system,
and elevation support with the
interactive Material 3 demo:<topic_end>
<topic_start>More information
To learn more about Material Design and Flutter,
check out:
<topic_end>
<topic_start>Migrate to Material 3
<topic_end>
<topic_start>
Summary
The Material library has been updated to match the Material 3 Design spec.
Changes include new components and component themes, updated component visuals,
and much more. Many of these updates are seamless. You’ll see the new version
of an affected widget when recompiling your app against the 3.16 (or later)
release. But some manual work is also required to complete the migration.<topic_end>
<topic_start>
Migration guide
Prior to the 3.16 release, you could opt in to the Material 3 changes by
setting the useMaterial3 flag to true. As of the Flutter 3.16 release
(November 2023), useMaterial3 is true by default.By the way, you can revert to Material 2 behavior in your app by setting the
useMaterial3 to false. However, this is just a temporary solution. The
useMaterial3 flag and the Material 2 implementation will eventually be
removed as part of Flutter’s deprecation policy.<topic_end>
<topic_start>
Colors
The default values for ThemeData.colorScheme are updated to match
the Material 3 Design spec.The ColorScheme.fromSeed constructor generates a ColorScheme
derived from the given seedColor. The colors generated by this
constructor are designed to work well together and meet contrast
requirements for accessibility in the Material 3 Design system.When updating to the 3.16 release, your UI might look a little strange
without the correct ColorScheme. To fix this, migrate to the
ColorScheme generated from the ColorScheme.fromSeed constructor.Code before migration:Code after migration:To generate a content-based dynamic color scheme, use the
ColorScheme.fromImageProvider static method. For an example of generating a
color scheme, check out the ColorScheme from a network image sample.Changes to Flutter Material 3 include a new background color.
ColorScheme.surfaceTint indicates an elevated widget.
Some widgets use different colors.To return your app’s UI to its previous behavior (which we don’t recommend):Code before migration:Code after migration:The ColorScheme.surfaceTint value indicates a component’s elevation in
Material 3. Some widgets might use both surfaceTint and shadowColor to
indicate elevation (for example, Card and ElevatedButton) and others might
only use surfaceTint to indicate elevation (such as AppBar).To return to the widget’s previous behavior, set, set Colors.transparent
to ColorScheme.surfaceTint in the theme. To differentiate a widget’s shadow
from the content (when it has no shadow), set the ColorScheme.shadow color to
the shadowColor property in the widget theme without a default shadow color.Code before migration:Code after migration:The ElevatedButton now styles itself with a new combination of colors.
Previously, when the useMaterial3 flag was set to false, ElevatedButton
styled itself with ColorScheme.primary for the background and
ColorScheme.onPrimary for the foreground. To achieve the same visuals, switch
to the new FilledButton widget without the elevation changes or drop shadow.Code before migration:Code after migration:<topic_end>
<topic_start>
Typography
The default values for ThemeData.textTheme are updated to match the
Material 3 defaults. Changes include updated font size, font weight, letter
spacing, and line height. For more details, check out the TextTheme
documentation.As shown in the following example, prior to the 3.16 release, when a Text
widget with a long string using TextTheme.bodyLarge in a constrained layout
wrapped the text into two lines. However, the 3.16 release wraps the text into
three lines. If you must achieve the previous behavior, adjust the text style
and, if necessary, the letter spacing.Code before migration:Code after migration:<topic_end>
<topic_start>
Components
Some components couldn’t merely be updated to match the Material 3 Design spec
but needed a whole new implementation. Such components require manual migration
since the Flutter SDK doesn’t know what, exactly, you want.Replace the Material 2 style BottomNavigationBar widget with the new
NavigationBar widget. It’s slightly taller, contains pill-shaped
navigation indicators, and uses new color mappings.Code before migration:Code after migration:Check out the complete sample on
migrating from BottomNavigationBar to NavigationBar.Replace the Drawer widget with NavigationDrawer, which provides
pill-shaped navigation indicators, rounded corners, and new color mappings.Code before migration:Code after migration:Check out the complete sample on migrating from Drawer to NavigationDrawer.Material 3 introduces medium and large app bars that display a larger headline
before scrolling. Instead of a drop shadow, ColorScheme.surfaceTint color
is used create a separation from the content when scrolling.The following code demonstrates how to implement the medium app bar:There are now two types of TabBar widgets: primary and secondary.
Secondary tabs are used within a content area to further separate
related content and establish hierarchy. Check out the TabBar.secondary
example.The new TabBar.tabAlignment property specifies the horizontal alignment
of the tabs.The following sample shows how to modify tab alignment in a scrollable TabBar:SegmentedButton, an updated version of ToggleButtons,
uses fully rounded corners, differs in layout height and
size, and uses a Dart Set to determine selected items.Code before migration:Code after migration:Check out the complete sample on
migrating from ToggleButtons to SegmentedButton.<topic_end>
<topic_start>New components
<topic_end>
<topic_start>
Timeline
In stable release: 3.16<topic_end>
<topic_start>
References
Documentation:API documentation:Relevant issues:Relevant PRs:
<topic_end>
<topic_start>Text
<topic_end>
<topic_start>
Topics
<topic_end>
<topic_start>Flutter's fonts and typography
Typography covers the style and appearance of

will eventually be deprecated according to

Flutter’s deprecation policy.For most Flutter widgets, upgrading to Material 3

is seamless. But some widgets couldn’t be

updated—entirely new implementations were needed,

such as NavigationBar.

You must make these changes to your code manually.

Until your app is entirely updated,

the UI might look or act a bit strange.

You can find the entirely new Material components by

visiting the Affected widgets page.Explore the updated components, typography, color system,

and elevation support with the

interactive Material 3 demo:<topic_end>

<topic_start>More information

To learn more about Material Design and Flutter,

check out:

<topic_end>

<topic_start>Migrate to Material 3

<topic_end>

<topic_start>

Summary

The Material library has been updated to match the Material 3 Design spec.

Changes include new components and component themes, updated component visuals,

and much more. Many of these updates are seamless. You’ll see the new version

of an affected widget when recompiling your app against the 3.16 (or later)

release. But some manual work is also required to complete the migration.<topic_end>

<topic_start>

Migration guide

Prior to the 3.16 release, you could opt in to the Material 3 changes by

setting the useMaterial3 flag to true. As of the Flutter 3.16 release

(November 2023), useMaterial3 is true by default.By the way, you can revert to Material 2 behavior in your app by setting the

useMaterial3 to false. However, this is just a temporary solution. The

useMaterial3 flag and the Material 2 implementation will eventually be

removed as part of Flutter’s deprecation policy.<topic_end>

<topic_start>

Colors

The default values for ThemeData.colorScheme are updated to match

the Material 3 Design spec.The ColorScheme.fromSeed constructor generates a ColorScheme

derived from the given seedColor. The colors generated by this

constructor are designed to work well together and meet contrast

requirements for accessibility in the Material 3 Design system.When updating to the 3.16 release, your UI might look a little strange

without the correct ColorScheme. To fix this, migrate to the

ColorScheme generated from the ColorScheme.fromSeed constructor.Code before migration:Code after migration:To generate a content-based dynamic color scheme, use the

ColorScheme.fromImageProvider static method. For an example of generating a

color scheme, check out the ColorScheme from a network image sample.Changes to Flutter Material 3 include a new background color.

ColorScheme.surfaceTint indicates an elevated widget.

Some widgets use different colors.To return your app’s UI to its previous behavior (which we don’t recommend):Code before migration:Code after migration:The ColorScheme.surfaceTint value indicates a component’s elevation in

Material 3. Some widgets might use both surfaceTint and shadowColor to

indicate elevation (for example, Card and ElevatedButton) and others might

only use surfaceTint to indicate elevation (such as AppBar).To return to the widget’s previous behavior, set, set Colors.transparent

to ColorScheme.surfaceTint in the theme. To differentiate a widget’s shadow

from the content (when it has no shadow), set the ColorScheme.shadow color to

the shadowColor property in the widget theme without a default shadow color.Code before migration:Code after migration:The ElevatedButton now styles itself with a new combination of colors.

Previously, when the useMaterial3 flag was set to false, ElevatedButton

styled itself with ColorScheme.primary for the background and

ColorScheme.onPrimary for the foreground. To achieve the same visuals, switch

to the new FilledButton widget without the elevation changes or drop shadow.Code before migration:Code after migration:<topic_end>

<topic_start>

Typography

The default values for ThemeData.textTheme are updated to match the

Material 3 defaults. Changes include updated font size, font weight, letter

spacing, and line height. For more details, check out the TextTheme

documentation.As shown in the following example, prior to the 3.16 release, when a Text

widget with a long string using TextTheme.bodyLarge in a constrained layout

wrapped the text into two lines. However, the 3.16 release wraps the text into

three lines. If you must achieve the previous behavior, adjust the text style

and, if necessary, the letter spacing.Code before migration:Code after migration:<topic_end>

<topic_start>

Components

Some components couldn’t merely be updated to match the Material 3 Design spec

but needed a whole new implementation. Such components require manual migration

since the Flutter SDK doesn’t know what, exactly, you want.Replace the Material 2 style BottomNavigationBar widget with the new

NavigationBar widget. It’s slightly taller, contains pill-shaped

navigation indicators, and uses new color mappings.Code before migration:Code after migration:Check out the complete sample on

migrating from BottomNavigationBar to NavigationBar.Replace the Drawer widget with NavigationDrawer, which provides

pill-shaped navigation indicators, rounded corners, and new color mappings.Code before migration:Code after migration:Check out the complete sample on migrating from Drawer to NavigationDrawer.Material 3 introduces medium and large app bars that display a larger headline

before scrolling. Instead of a drop shadow, ColorScheme.surfaceTint color

is used create a separation from the content when scrolling.The following code demonstrates how to implement the medium app bar:There are now two types of TabBar widgets: primary and secondary.

Secondary tabs are used within a content area to further separate

related content and establish hierarchy. Check out the TabBar.secondary

example.The new TabBar.tabAlignment property specifies the horizontal alignment

of the tabs.The following sample shows how to modify tab alignment in a scrollable TabBar:SegmentedButton, an updated version of ToggleButtons,

uses fully rounded corners, differs in layout height and

size, and uses a Dart Set to determine selected items.Code before migration:Code after migration:Check out the complete sample on

migrating from ToggleButtons to SegmentedButton.<topic_end>

<topic_start>New components

<topic_end>

<topic_start>

Timeline

In stable release: 3.16<topic_end>

<topic_start>

References

Documentation:API documentation:Relevant issues:Relevant PRs:

<topic_end>

<topic_start>Text

<topic_end>

<topic_start>

Topics

<topic_end>

<topic_start>Flutter's fonts and typography

Typography covers the style and appearance of