Flutter global key current context null

by

Flutter Global Key Current Context Null:

When facing the “Flutter Global Key Current Context Null” issue, it means that you are trying to access the current context where a global key is required, but none is available. This commonly occurs when using GlobalKey within a widget that is not yet fully built or attached to the widget tree.

Example:


import 'package:flutter/material.dart';

class MyWidget extends StatefulWidget {
  @override
  _MyWidgetState createState() => _MyWidgetState();
}

class _MyWidgetState extends State {
  GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: _scaffoldKey,
      appBar: AppBar(
        title: Text('My Widget'),
      ),
      body: RaisedButton(
        child: Text('Show SnackBar'),
        onPressed: () {
          _scaffoldKey.currentState.showSnackBar(
            SnackBar(
              content: Text('Hello!'),
            ),
          );
        },
      ),
    );
  }
}

void main() {
  runApp(MaterialApp(
    home: MyWidget(),
  ));
}

In the example above, a GlobalKey of type ScaffoldState is being used to access the Scaffold’s state to show a SnackBar. The GlobalKey is assigned to the Scaffold’s key property, and then used in the onPressed event of a RaisedButton.

If the GlobalKey was used before the build method is called, or if the widget is not yet attached to the widget tree, the current context will be null, resulting in the “Flutter Global Key Current Context Null” error.

Solution:

To solve this issue, make sure you are using the GlobalKey within the appropriate lifecycle methods or after the widget has been attached to the widget tree.

For example, in the previous case, you can move the initialization of the GlobalKey to the initState method:


import 'package:flutter/material.dart';

class MyWidget extends StatefulWidget {
  @override
  _MyWidgetState createState() => _MyWidgetState();
}

class _MyWidgetState extends State {
  GlobalKey<ScaffoldState> _scaffoldKey;

  @override
  void initState() {
    super.initState();
    _scaffoldKey = GlobalKey<ScaffoldState>();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: _scaffoldKey,
      appBar: AppBar(
        title: Text('My Widget'),
      ),
      body: RaisedButton(
        child: Text('Show SnackBar'),
        onPressed: () {
          _scaffoldKey.currentState.showSnackBar(
            SnackBar(
              content: Text('Hello!'),
            ),
          );
        },
      ),
    );
  }
}

void main() {
  runApp(MaterialApp(
    home: MyWidget(),
  ));
}

By initializing the GlobalKey within the initState method, you ensure that it is properly assigned a value when the widget is being built and attached to the widget tree.

Leave a comment