There are multiple heroes that share the same tag within a subtree

I am trying to navigate from one screen to another with route. When I hit the button for the page to move to the route provided I get the error

I/flutter ( 8790): Another exception was thrown: There are multiple heroes that share the same tag within a subtree.

Here's the code:

Routes:

 <String, WidgetBuilder>{
    '/first':(BuildContext context) =>NavigatorOne() ,
    '/second':(BuildContext context) =>NavigatorTwo(),
    '/third':(BuildContext context) =>NavigatorThree(),

  },

Navigator.of(context).pushNamed('/first');
Navigator.of(context).pushNamed('/second');
Navigator.of(context).pushNamed('/third');

class NavigatorOne extends StatefulWidget {
  @override
  _NavigatorOneState createState() =>  _NavigatorOneState();
}

class _NavigatorOneState extends State<NavigatorOne> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      
      appBar: AppBar(),
      body: Container(
      color: Colors.green,
      child: RaisedButton(child: Text(' one 1'),onPressed: (){
        Navigator.of(context).pushNamed('/second');
      },),
    ),
    ); 
  }
}

And The Error:

══╡ EXCEPTION CAUGHT BY SCHEDULER LIBRARY ╞═════════════════════════════════════════════════════════ I/flutter (21786): The following assertion was thrown during a scheduler callback: I/flutter (21786): There are multiple heroes that share the same tag within a subtree. I/flutter (21786): Within each subtree for which heroes are to be animated (typically a PageRoute subtree), each Hero I/flutter (21786): must have a unique non-null tag. I/flutter (21786): In this case, multiple heroes had the following tag: <default FloatingActionButton tag>

How do I solve this?

I have encountered this before, and it was because I had two FloatingAction buttons on one screen, I had to add a heroTag property + value per FloatingActionButton in order for the error to go away.

Example:

FloatingActionButton(
    heroTag: "btn1",
    ...
)

FloatingActionButton(
    heroTag: "btn2",
    ...
)

From the example code you provided it doesn't appear that you have a FloatingActionButton, but from the error it does seem to reference it:

I/flutter (21786): In this case, multiple heroes had the following tag: default FloatingActionButton tag

Perhaps you used it on the page you were navigating to which then triggered the error. Note that if you're using a programmatic way of creating tagged heroes, you will need to find a way of giving them different tags. For example, if you have a ListView.builder() creating FloatingActionButtons, try passing tags with string formatting so each button has a different tag, e.g.: heroTag: "btn$index".

In any event, hope that helps someone.

You can set a unique id or only set null:

FloatingActionButton(
  heroTag: null,
  ...
)

Just for Readers in the future:

in appreciate to @m.vincent comment, what cause this error for me is that i was using Hero inside SliverChildBuilderDelegate which (obviously) has an index, so i used the index with the tag like 'tag$index' like this

SliverChildBuilderDelegate(
    (BuildContext context, int index) {
      return Column(
          mainAxisSize: MainAxisSize.min,
          children: <Widget>[
            Hero(
              tag: 'tagImage$index',
              child: Image.asset(
                'image source here',
              ),
            ),

NOTE : this may happen with any widget with index created children like ListView.Builder

For me, just adding a unique heroTag to my FloatingActionButtons didn't work. I ended up wrapping the heroTag in a Text widget and that solved the problem for me.

new FloatingActionButton(
    heroTag: Text("btn1"),
    ...
)

new FloatingActionButton(
    heroTag: Text("btn2"),
    ...
)

Add as many widgets as you like with hero tags as Strings

  Widget floatingButt(Function function, IconData icon, String heroTag) {
    return FloatingActionButton(
      onPressed: function,
      heroTag: heroTag,
      materialTapTargetSize: MaterialTapTargetSize.padded,
      backgroundColor: Constants.primaryColor, // from your values file
      child: Icon(
        icon,
        size: 36.0,
      ),
    );
  }

I went through same Error. It is because of use of buttons like floating action button multiple times in single screen.
Previously I used a floating action button instead I changed it to a gesture detector to use ontap so it worked

  GestureDetector(
              
              //backgroundColor: Colors.amber[100],
              onTap: add,
              child: Icon(
                FontAwesomeIcons.plus,
                size: 30,
              ),
            ),
            SizedBox(
              width: 20,
            ),
            GestureDetector(
             // heroTag: "btn2",
             // backgroundColor: Colors.amber[100],
              onTap: sub,
              child: Icon(FontAwesomeIcons.minus, size: 30),
            ),

This is correct because according to flutter documentations, it should be one Floating Action Button per route (Screen) unless you explicit set the hero tag.

Flutter Docs

> if this is not explicitly set, then there can only be one > FloatingActionButton per route (that is, per screen), since otherwise > there would be a tag conflict (multiple heroes on one route can't have > the same tag). The material design specification recommends only using > one floating action button per screen.

Simply set tag: Uuid() if having multiple items with the same tag.

Simple solution of this heroTag issue is to provide this property as unique value. Either it can be a String value. In my case i provided it a String casted index value. And following is my solution which is working perfectly

FloatingActionButton(
  onPressed: (){ 
    print(index); 
    Navigator.push( context, 
       MaterialPageRoute( builder: (context)=> AddLead()
       ),
     );
    }, 
  heroTag: '$index',
  child: Image.asset('assets/pencil.png',height: 30, width: 30,), backgroundColor: Constants.myColor, 
),

for more information follow this link https://wise4rmgodadmob.medium.com/how-to-solve-there-are-multiple-heroes-that-share-the-same-tag-within-a-subtree-a5146fdec2b8