text
stringlengths 1
372
|
|---|
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>
|
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