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<code_end>
to learn more ways to manage state, check out state management.
<topic_end>
<topic_start>
animations
two main types of UI animations exist.
<topic_end>
<topic_start>
implicit animation
SwiftUI and flutter take a similar approach to animation.
in both frameworks, you specify parameters like duration, and curve.
in SwiftUI, you use the animate() modifier to handle implicit
animation.
flutter includes widgets for implicit animation.
this simplifies animating common widgets.
flutter names these widgets with the following format: AnimatedFoo.
for example: to rotate a button, use the AnimatedRotation class.
this animates the transform.rotate widget.
<code_start>
AnimatedRotation(
duration: const duration(seconds: 1),
turns: turns,
curve: Curves.easeIn,
child: TextButton(
onPressed: () {
setState(() {
turns += .125;
});
},
child: const Text('Tap me!')),
),
<code_end>
flutter allows you to create custom implicit animations.
to compose a new animated widget, use the TweenAnimationBuilder.
<topic_end>
<topic_start>
explicit animation
for explicit animations, SwiftUI uses the withAnimation() function.
flutter includes explicitly animated widgets with names formatted
like FooTransition.
one example would be the RotationTransition class.
flutter also allows you to create a custom explicit animation using
AnimatedWidget or AnimatedBuilder.
to learn more about animations in flutter, see animations overview.
<topic_end>
<topic_start>
drawing on the screen
in SwiftUI, you use CoreGraphics to draw lines and shapes to the
screen.
flutter has an API based on the canvas class,
with two classes that help you draw:
CustomPaint that requires a painter:
<code_start>
CustomPaint(
painter: SignaturePainter(_points),
size: size.infinite,
),
<code_end>
CustomPainter that implements your algorithm to draw to the canvas.
<code_start>
class SignaturePainter extends CustomPainter {
SignaturePainter(this.points);
final List<Offset?> points;
@override
void paint(Canvas canvas, size size) {
final paint paint = paint()
..color = colors.black
..strokeCap = StrokeCap.round
..strokeWidth = 5;
for (int i = 0; i < points.length - 1; i++) {
if (points[i] != null && points[i + 1] != null) {
canvas.drawLine(points[i]!, points[i + 1]!, paint);
}
}
}
@override
bool shouldRepaint(SignaturePainter oldDelegate) =>
oldDelegate.points != points;
}
<code_end>
<topic_end>
<topic_start>
navigation
this section explains how to navigate between pages of an app,
the push and pop mechanism, and more.
<topic_end>
<topic_start>
navigating between pages
developers build iOS and macOS apps with different pages called
navigation routes.
in SwiftUI, the NavigationStack represents this stack of pages.
the following example creates an app that displays a list of persons.
to display a person’s details in a new navigation link,
tap on that person.
if you have a small flutter app without complex linking,
use navigator with named routes.
after defining your navigation routes,