How do I solve the 'Failed assertion: boolean expression must not be null' exception in Flutter

Question

I was working on a Flutter application and kept receiving this error String in the logcat.

Failed assertion: boolean expression must not be null
         


        

Answer 1

This problem occurs when one of your defined boolean type variable is not initialized with default value, and you try to use and assign it somewhere as value. example maybe you have you bool isEnabled ; is not defined as should bool isEnabled = false; or bool isEnabled = true; and you try to use it like readOnly: isEnabled,

To avoid these to ensure isEnabled won't be null. Here is a kind of example of how we can avoid these

bool isChecked = false;

Checkbox(
  value: isChecked,  // initialized with `true/false` also avoids the error,
  onChanged ...
)