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flutter_docs

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itemCount: data.length,
itemBuilder: (context, index) {
return text(data[index]);
},
);
<code_end>
to learn how to implement an infinite scrolling list, see the official
infinite_list sample.
<topic_end>
<topic_start>
how do i use a canvas to draw or paint?
in react native, canvas components aren’t present
so third party libraries like react-native-canvas are used.
in flutter, you can use the CustomPaint
and CustomPainter classes to draw to the canvas.
the following example shows how to draw during the paint phase using the
CustomPaint widget. it implements the abstract class, CustomPainter,
and passes it to CustomPaint’s painter property.
CustomPaint subclasses must implement the paint()
and shouldRepaint() methods.
<code_start>
class MyCanvasPainter extends CustomPainter {
const MyCanvasPainter();
@override
void paint(Canvas canvas, size size) {
final paint paint = paint()..color = colors.amber;
canvas.drawCircle(const offset(100, 200), 40, paint);
final paint paintRect = paint()..color = Colors.lightBlue;
final rect rect = Rect.fromPoints(
const offset(150, 300),
const offset(300, 400),
);
canvas.drawRect(rect, paintRect);
}
@override
bool shouldRepaint(MyCanvasPainter oldDelegate) => false;
}
class MyCanvasWidget extends StatelessWidget {
const MyCanvasWidget({super.key});
@override
widget build(BuildContext context) {
return const scaffold(
body: CustomPaint(painter: MyCanvasPainter()),
);
}
}
<code_end>
<topic_end>
<topic_start>
layouts
<topic_end>
<topic_start>
how do i use widgets to define layout properties?
in react native, most of the layout can be done with the props
that are passed to a specific component.
for example, you could use the style prop on the view component
in order to specify the flexbox properties.
to arrange your components in a column, you would specify a prop such as:
flexDirection: 'column'.
in flutter, the layout is primarily defined by widgets
specifically designed to provide layout,
combined with control widgets and their style properties.
for example, the column and row widgets
take an array of children and align them
vertically and horizontally respectively.
a container widget takes a combination of
layout and styling properties, and a
center widget centers its child widgets.
<code_start>
@override
widget build(BuildContext context) {
return center(
child: column(
children: <widget>[
container(
color: colors.red,
width: 100,
height: 100,
),
container(
color: colors.blue,
width: 100,
height: 100,
),
container(
color: colors.green,
width: 100,
height: 100,
),
],
),
);
<code_end>
flutter provides a variety of layout widgets in its core widget library.
for example, padding, align, and stack.
for a complete list, see layout widgets.
<topic_end>
<topic_start>
how do i layer widgets?
in react native, components can be layered using absolute positioning.