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theme: ThemeData(
colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
textSelectionTheme:
const TextSelectionThemeData(selectionColor: colors.red)),
home: const SampleAppPage(),
);
}
}
<code_end>
<topic_end>
<topic_start>
how do i add style themes?
in react native, common themes are defined for
components in stylesheets and then used in components.
in flutter, create uniform styling for almost everything
by defining the styling in the ThemeData
class and passing it to the theme property in the
MaterialApp widget.
<code_start>
@override
widget build(BuildContext context) {
return MaterialApp(
theme: ThemeData(
primaryColor: colors.cyan,
brightness: brightness.dark,
),
home: const StylingPage(),
);
}
<code_end>
a theme can be applied even without using the MaterialApp widget.
the theme widget takes a ThemeData in its data parameter
and applies the ThemeData to all of its children widgets.
<code_start>
@override
widget build(BuildContext context) {
return theme(
data: ThemeData(
primaryColor: colors.cyan,
brightness: brightness,
),
child: scaffold(
backgroundColor: Theme.of(context).primaryColor,
//...
),
);
}
<code_end>
<topic_end>
<topic_start>
state management
state is information that can be read synchronously
when a widget is built or information
that might change during the lifetime of a widget.
to manage app state in flutter,
use a StatefulWidget paired with a state object.
for more information on ways to approach managing state in flutter,
see state management.
<topic_end>
<topic_start>
the StatelessWidget
a StatelessWidget in flutter is a widget
that doesn’t require a state change—
it has no internal state to manage.
stateless widgets are useful when the part of the user interface
you are describing does not depend on anything other than the
configuration information in the object itself and the
BuildContext in which the widget is inflated.
AboutDialog, CircleAvatar, and text are examples
of stateless widgets that subclass StatelessWidget.
<code_start>
import 'package:flutter/material.dart';
void main() => runApp(
const MyStatelessWidget(
text: 'statelesswidget example to show immutable data',
),
);
class MyStatelessWidget extends StatelessWidget {
const MyStatelessWidget({
super.key,
required this.text,
});
final string text;
@override
widget build(BuildContext context) {
return center(
child: text(
text,
textDirection: TextDirection.ltr,
),
);
}
}
<code_end>
the previous example uses the constructor of the MyStatelessWidget
class to pass the text, which is marked as final.
this class extends StatelessWidget—it contains immutable data.
the build method of a stateless widget is typically called
in only three situations:
<topic_end>