use_build_context_synchronously

Don't use 'BuildContext's across async gaps, guarded by an unrelated 'mounted' check.

Don't use 'BuildContext's across async gaps.

The analyzer produces this diagnostic when a BuildContext is referenced by a StatefulWidget after an asynchronous gap without first checking the mounted property.

Storing a BuildContext for later use can lead to difficult-to-diagnose crashes. Asynchronous gaps implicitly store a BuildContext, making them easy to overlook for diagnosis.

The following code produces this diagnostic because the context is passed to a constructor after the await:

import 'package:flutter/material.dart';
​
class MyWidget extends Widget {
  void onButtonTapped(BuildContext context) async {
    await Future.delayed(const Duration(seconds: 1));
    Navigator.of(context).pop();
  }
}

If you can remove the asynchronous gap, do so:

import 'package:flutter/material.dart';
​
class MyWidget extends Widget {
  void onButtonTapped(BuildContext context) {
    Navigator.of(context).pop();
  }
}

If you can't remove the asynchronous gap, then use mounted to guard the use of the context:

import 'package:flutter/material.dart';
​
class MyWidget extends Widget {
  void onButtonTapped(BuildContext context) async {
    await Future.delayed(const Duration(seconds: 1));
    if (context.mounted) {
      Navigator.of(context).pop();
    }
  }
}