Transitions Hero et mouvements d’éléments partagés
Coordonnez les composants Hero et les navettes de transition personnalisées pour créer des transitions d’écran soignées.
Transitions Hero et mouvements d’éléments partagés est une leçon Flutter Mobile Development gratuite sur CoddyKit. Ceci est la leçon 3 sur 4. Tu peux lire la leçon complète ci-dessous gratuitement — puis la pratiquer en direct dans le navigateur avec un éditeur de code intégré et un tuteur IA 24/7. Elle fait partie du parcours d'apprentissage Flutter Mobile Development, et ta progression se synchronise sur le web et l'application CoddyKit. Le cours Flutter Mobile Development comprend 4 leçons au total.
Certaines parties de cette leçon n'ont pas encore été traduites et s'affichent en anglais.
What Shared Element Motion Means
A Hero transition animates a single widget so it appears to fly from one screen to another during a route push or pop. Instead of the user losing track of an element across screens, the same visual object morphs in place.
- Think of a thumbnail in a list that expands into a full-screen detail image.
- Flutter computes the start and end rectangles and tweens the widget between them.
- This continuity is what designers call shared element motion.
In this lesson you will coordinate Hero widgets and customize the flight shuttle that actually renders during the in-between frames.
The Hero Widget Contract
To create a Hero animation you wrap the source and destination widgets in a Hero widget and give both the same tag. The tag is how Flutter pairs them across routes.
- Tags must be unique per screen but identical between the two screens.
- If two Heroes on the same screen share a tag, Flutter throws an assertion at navigation time.
Below, a product thumbnail on the list screen uses the product id as its tag.
Hero(
tag: 'product-${product.id}',
child: Image.network(
product.thumbnailUrl,
width: 80,
height: 80,
fit: BoxFit.cover,
),
)Matching the Destination Hero
The detail screen must wrap its large image in a Hero with the exact same tag. When you push the detail route, Flutter detects both Heroes and starts the flight automatically.
- The child widgets do not have to be identical — only the tag must match.
- Here the destination is a full-width image, while the source was an 80x80 thumbnail.
Hero(
tag: 'product-${product.id}',
child: Image.network(
product.imageUrl,
width: double.infinity,
height: 320,
fit: BoxFit.cover,
),
)How Tags Drive Pairing
During a route transition Flutter scans both the outgoing and incoming routes for Heroes, then builds a map keyed by tag. Only tags present on both routes animate; an unmatched Hero simply fades with its page.
Because tags are matched by equality, you can use any object as a tag — strings, ints, or enums — as long as == and hashCode behave correctly.
bool heroesMatch(Object tagA, Object tagB) {
return tagA == tagB;
}
void main() {
print(heroesMatch('product-7', 'product-7')); // true -> flies
print(heroesMatch('product-7', 'product-9')); // false -> fades
print(heroesMatch(42, 42)); // true
}The Default Flight Shuttle
The widget rendered during the flight is called the flight shuttle. By default Flutter uses the destination Hero's child for the entire flight, cross-fading where needed.
This works well when the two children look alike. But when the source and destination have very different shapes — for example a square avatar becoming a rounded banner — the default can look like an abrupt swap. That is when you supply a custom flightShuttleBuilder.
Customizing the Flight Shuttle
The flightShuttleBuilder lets you control exactly what is painted mid-flight. Its signature gives you the animation, the direction (push or pop), and both Hero contexts.
flightDirectionisHeroFlightDirection.pushor.pop.- Return any widget; it will be positioned inside the interpolated rectangle for you.
Here we rotate the child slightly as it flies to add polish.
Hero(
tag: 'product-${product.id}',
flightShuttleBuilder: (
BuildContext flightContext,
Animation<double> animation,
HeroFlightDirection direction,
BuildContext fromContext,
BuildContext toContext,
) {
return RotationTransition(
turns: Tween<double>(begin: 0, end: 0.05).animate(animation),
child: toContext.widget,
);
},
child: Image.network(product.imageUrl, fit: BoxFit.cover),
)Cross-Fading Between Two Children
A common shuttle pattern is cross-fading from the source child to the destination child so the morph reads smoothly. You can drive a FadeTransition from the same flight animation.
- On push, fade the source out and the destination in.
- On pop, reverse the roles using
flightDirection.
Widget buildShuttle(
BuildContext flightContext,
Animation<double> animation,
HeroFlightDirection direction,
BuildContext fromContext,
BuildContext toContext,
) {
final Widget fromHero = (fromContext.widget as Hero).child;
final Widget toHero = (toContext.widget as Hero).child;
final bool isPush = direction == HeroFlightDirection.push;
return Stack(
fit: StackFit.expand,
children: [
FadeTransition(
opacity: Tween<double>(begin: isPush ? 1 : 0, end: isPush ? 0 : 1)
.animate(animation),
child: fromHero,
),
FadeTransition(
opacity: Tween<double>(begin: isPush ? 0 : 1, end: isPush ? 1 : 0)
.animate(animation),
child: toHero,
),
],
);
}Shaping the Flight Path
By default the Hero moves along a straight line. You can bend that path with createRectTween, which controls how the bounding rectangle is interpolated.
Material's MaterialRectArcTween gives a curved, more natural arc — the same motion Material Design recommends for shared element transitions.
import 'package:flutter/material.dart';
RectTween arcTween(Rect? begin, Rect? end) {
return MaterialRectArcTween(begin: begin, end: end);
}
// Usage on the Hero:
// Hero(
// tag: 'product-7',
// createRectTween: arcTween,
// child: ...,
// )Avoiding Tag Collisions in Lists
The most frequent Hero bug is a duplicate tag on a single screen. In a ListView of items, every Hero needs a tag unique to its data row.
- Never use a constant string like
'hero'for all items. - Derive the tag from a stable identity such as the model id.
This helper guarantees uniqueness when building list rows.
String heroTagFor(String screen, Object id) {
return '$screen::$id';
}
void main() {
final ids = [1, 2, 2, 3];
final tags = <String>{};
for (final id in ids) {
final tag = heroTagFor('list', id);
if (!tags.add(tag)) {
print('Collision on $tag');
} else {
print('OK $tag');
}
}
}Wrapping Heroes in Material
When a Hero's child has elevation, rounded corners, or ink — like a Card or Material surface — the flight can show clipped or square corners because the in-flight widget is detached from its original ancestors.
Wrap the shuttle (or the children) in a Material with type: MaterialType.transparency so text, shadows, and clipping render correctly mid-flight.
Hero(
tag: 'card-${item.id}',
flightShuttleBuilder: (ctx, anim, dir, from, to) {
return Material(
type: MaterialType.transparency,
child: (to.widget as Hero).child,
);
},
child: Material(
type: MaterialType.transparency,
child: ProductCard(item: item),
),
)Coordinating Hero with Rive
In this track we pair Hero transitions with Rive animations for richer motion. A clean approach is to let the Hero handle position and size, while a Rive state machine plays a micro-animation on arrival.
- Drive a Rive
SMITriggerwhen the destination route finishes its transition. - Use
animation.addStatusListeneron the flight to fire the trigger atAnimationStatus.completed.
Keep the Hero shuttle simple; let Rive own the expressive part so the two systems do not fight over the same frames.
void fireOnArrival(Animation<double> animation, void Function() onArrived) {
animation.addStatusListener((status) {
if (status == AnimationStatus.completed) {
onArrived(); // e.g. riveTrigger.fire();
}
});
}Quick Check
You have a grid of avatars; tapping one pushes a profile screen. The avatar is a 56x56 circle, and the destination is a 200-tall rounded banner. The default flight looks like an abrupt swap and the corners flicker square during motion. Which combination best fixes this?
Recap
You now know how to build polished shared element transitions:
- Matching tags on source and destination Heroes drive the pairing; tags must be unique per screen and identical across screens.
- The flight shuttle is what renders mid-flight; customize it with
flightShuttleBuilderto cross-fade differing children. - Wrap shuttle content in a transparent Material to keep shadows, text, and rounded corners correct.
- Bend the path with
createRectTweenandMaterialRectArcTweenfor a natural arc. - Let Hero own position and hand expressive micro-motion to a Rive state machine, fired on
AnimationStatus.completed.
Combine these to make screen changes feel continuous and intentional.
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Questions Fréquemment Posées
La leçon « Transitions Hero et mouvements d’éléments partagés » est-elle gratuite ?
Oui — le texte complet de « Transitions Hero et mouvements d’éléments partagés » est gratuit à lire ici sur le web. Pour la pratiquer de manière interactive (un éditeur de code intégré et un tuteur IA 24/7) et déverrouiller le reste du cours Flutter Mobile Development, passe à CoddyKit PRO. Le cours Flutter Mobile Development comprend 4 leçons au total.
Qu'est-ce que j'apprendrai dans « Transitions Hero et mouvements d’éléments partagés » ?
Coordonnez les composants Hero et les navettes de transition personnalisées pour créer des transitions d’écran soignées. Tu pratiques Flutter Mobile Development avec du code pratique que tu exécutes directement dans le navigateur, et un tuteur IA 24/7 répond à tes questions au fur et à mesure que tu avances dans la leçon.
Dois-je avoir de l'expérience pour commencer Flutter Mobile Development ?
Aucune expérience préalable n'est requise. Flutter Mobile Development sur CoddyKit est structuré pour les débutants jusqu'aux apprenants avancés, donc tu peux commencer ici ou depuis le début et avancer à ton rythme. Ceci est la leçon 3 sur 4.
Combien de temps prend la leçon « Transitions Hero et mouvements d’éléments partagés » ?
La plupart des leçons CoddyKit prennent environ 5–10 minutes. Chacune est courte et interactive, tu progresses régulièrement et tu repiques exactement où tu t'es arrêté sur le web et l'app.
Peux-tu écrire et exécuter du code dans cette leçon Flutter Mobile Development ?
Oui. Chaque leçon Flutter Mobile Development inclut un éditeur de code intégré, tu écris et exécutes du vrai code directement dans ton navigateur et tu reçois des retours IA instantanés — aucune configuration locale requise.
Toutes les leçons de ce cours
- Intégration des ressources et contrôleurs Rive
- Machines à états et mouvements pilotés par les entrées
- Transitions Hero et mouvements d’éléments partagés
- AnimationControllers décalés et chorégraphiés