Question

如果用户成功创建了一个项目，我将使用新的ScaffoldMessenger来显示小吃栏。显示小吃栏时，我将应用程序导航到仪表板。但是，一旦击中仪表板，就会在子树中共享同一标签的多个英雄会引发错误。我在仪表板上没有使用任何Hero小部件，并且有一个FloatingActionButton，但其hero参数设置为null。

示例代码：

ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(
          content: Text('A SnackBar has been shown.'),
          animation: null,
        ),
      );
Navigator.pushReplacementNamed(context, '/dashboard');

哪个会导致此错误：

The following assertion was thrown during a scheduler callback:
There are multiple heroes that share the same tag within a subtree.

Within each subtree for which heroes are to be animated (i.e. a PageRoute subtree), each Hero must have a unique non-null tag.
In this case, multiple heroes had the following tag: <SnackBar Hero tag - Text("A SnackBar has been shown.")>

Within each subtree for which heroes are to be animated (i.e. a PageRoute subtree), each Hero must have a unique non-null tag.
In this case, multiple heroes had the following tag: <SnackBar Hero tag - Text("A SnackBar has been shown.")>

Here is the subtree for one of the offending heroes: Hero
    tag: <SnackBar Hero tag - Text("A SnackBar has been shown.")>
    state: _HeroState#7589f
When the exception was thrown, this was the stack
#0      Hero._allHeroesFor.inviteHero.<anonymous closure>
#1      Hero._allHeroesFor.inviteHero
package:flutter/…/widgets/heroes.dart:277
#2      Hero._allHeroesFor.visitor
package:flutter/…/widgets/heroes.dart:296
#3      ComponentElement.visitChildren
package:flutter/…/widgets/framework.dart:4729
#4      Hero._allHeroesFor.visitor
package:flutter/…/widgets/heroes.dart:309
...

Answer 1

我遇到了同样的问题。如果您有嵌套的脚手架，就会发生这种情况。 ScaffoldMessenger 想要将 Snackbar 发送到所有 Scaffolds。要解决此问题，您需要使用 ScaffoldMessenger 包裹您的 Scaffold。这可确保您只有一个 Scaffold 收到 Snackbar。

ScaffoldMessenger(
  child: Scaffold(
    body: ..
    ),
)

Answer 2

我通过在下一个事件循环迭代中运行调用解决了这个问题：

Future.delayed(const Duration(), () => 
    ScaffoldMessenger.of(context).showSnackBar(SnackBar(...)));

Answer 3

我遇到了同样的问题，并通过在用Navigator调用ScaffoldMessenger.of(context).removeCurrentSnackBar()之前删除SnackBar来解决了这个问题。

使用您的示例代码

：

ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(
          content: Text('A SnackBar has been shown.'),
          animation: null,
        ),
      );
ScaffoldMessenger.of(context).removeCurrentSnackBar();
Navigator.pushReplacementNamed(context, '/dashboard');

以下是对我有帮助的链接：https://flutter.dev/docs/release/breaking-changes/scaffold-messenger#migration-guide
希望对你有用

Answer 4

遇到了同样的问题，结果我有一个脚手架小部件在我的子树中返回另一个脚手架（哎呀）

如果是这样，那么您的小吃店会在两个脚手架上弹出，然后启动转换会导致错误。

ScaffoldMessenger抛出英雄动画错误

4 个答案: