19 December 2024 Leave a comment Tech-Help
When developing Flutter applications, you might encounter the error message: “There are multiple heroes that share the same tag within a subtree.” This error typically occurs when navigating between screens using Hero animations, and multiple Hero widgets with the same tag are detected within the same subtree. This article provides a clear guide on resolving this issue effectively.
Understanding the Error
The error arises because, within each subtree for which heroes are to be animated, each Hero must have a unique non-null tag. If multiple Hero widgets share the same tag on the same route, Flutter cannot determine which widget to animate, leading to the error.
Solution: Assign Unique Hero Tags
To resolve this error, ensure each Hero widget has a unique tag. Here’s a practical approach to achieving this:
- Explicit Tagging: Assign a distinct tag to each Hero widget. For example, if you have multiple FloatingActionButtons, you can set unique tags as shown below:
FloatingActionButton(
heroTag: "btn1",
...
)
FloatingActionButton(
heroTag: "btn2",
...
)
Hero(
tag: 'tagImage$index',
child: Image.asset(
'image source here',
),
)
Alternative Approaches
If you prefer not to assign specific tags, consider using the UniqueKey() class to generate a unique key for each Hero widget:
FloatingActionButton(
heroTag: UniqueKey(),
....
)
The UniqueKey class creates a key that is equal only to itself, ensuring uniqueness.
Practical Example
Consider the scenario where you have two distinct screens with FloatingActionButtons. By assigning each button a unique heroTag, you can navigate seamlessly without encountering the error:
class FirstScreen extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('First Screen')),
floatingActionButton: FloatingActionButton(
heroTag: 'fab1',
onPressed: () {
Navigator.of(context).pushNamed('/second');
},
child: Icon(Icons.navigate_next),
),
);
}
}
class SecondScreen extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('Second Screen')),
floatingActionButton: FloatingActionButton(
heroTag: 'fab2',
onPressed: () {
Navigator.of(context).pop();
},
child: Icon(Icons.navigate_before),
),
);
}
}
Enhancing Your Workflow with Repeato
When developing complex mobile applications, ensuring smooth navigation and UI interactions is crucial. Repeato, our no-code test automation tool, can streamline testing for Flutter apps, allowing you to efficiently create, run, and maintain automated tests. With its AI-powered capabilities, Repeato ensures that your app’s navigation flows work seamlessly, detecting and preventing errors like the “Multiple Heroes” issue before they reach production.
Explore more about Repeato and how it can enhance your app testing process on our Flutter Test Automation page.
