A globalkey was used multiple times inside one widget’s child list.

Explanation:

When a global key is used multiple times inside one widget’s child list, it can cause issues as each widget must have a unique key identifier.

Let’s consider an example to understand this better:

    
    // Incorrect usage of global key inside a widget
    Widget build(BuildContext context) {
        return Column(
            children: [
                Container(
                    key: GlobalKey<ContainerState>(),
                    child: Text("Widget 1"),
                ),
                Container(
                    key: GlobalKey<ContainerState>(), // Duplicate key used
                    child: Text("Widget 2"),
                ),
            ],
        );
    }
    
    

In the above example, a global key of type GlobalKey<ContainerState>() is used twice inside the list of children for the Column widget. This is not allowed and will cause errors.

To fix this issue, each widget within a list should have a unique key. The keys can be generated using the UniqueKey class or explicitly set using ValueKey or ObjectKey.

    
    // Correct usage of unique keys inside a widget
    Widget build(BuildContext context) {
        return Column(
            children: [
                Container(
                    key: GlobalKey<ContainerState>(),
                    child: Text("Widget 1"),
                ),
                Container(
                    key: GlobalKey<ContainerState>(), // Duplicate key removed
                    child: Text("Widget 2"),
                ),
            ],
        );
    }
    
    

In the correct example, the duplicate key has been removed, ensuring that each widget has a unique key.