ScaffoldMessenger 抛出英雄动画错误

Question

如果用户成功创建项目，我将使用新的 ScaffoldMessenger 来显示小吃栏。在显示小吃店时，我将应用导航到仪表板。但是一旦它点击仪表板，就会抛出一个子树错误中共享相同标签的多个英雄。我没有在仪表板中使用任何 Hero 小部件，我有一个 FloatingActionButton 但它的 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');

这导致此错误：

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

我有同样的问题。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。这确保您只有一个 Scaffold 收到 Snackbar。

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

Answer 2

我遇到了同样的问题，并通过在调用Navigatorwith之前删除 SnackBar 来修复它ScaffoldMessenger.of(context).removeCurrentSnackBar()。

使用您的示例代码看起来像这样：

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

这是帮助我的链接：https : //flutter.dev/docs/release/break-changes/scaffold-messenger#migration-guide
希望它对你有用