Error: not a constant expression flutter

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The error message “not a constant expression” in Flutter typically occurs when you try to assign a value to a variable that is not a compile-time constant. In Flutter, certain values can only be assigned to variables that are known at compile-time, such as literals or variables marked with the “const” keyword.

Here is an example to illustrate the error: 

    
      const int myValue = calculateValue(); // Error: 'calculateValue' is not a constant expression
      int calculateValue() {
        return 5;
      }

In the example above, the function ‘calculateValue()’ cannot be assigned to the constant variable ‘myValue’ because it is not a constant expression. To fix this error, you can change the variable to a non-constant and assign the return value of the function at runtime: 

    
      int myValue = calculateValue(); // No error
      int calculateValue() {
        return 5;
      }

By removing the “const” keyword on the variable declaration, Flutter allows assigning non-constant values to the variable.

It’s important to note that this error can also occur in other scenarios, such as using non-constant values in certain widget properties or when working with annotations. The key is to identify which part of your code is trying to assign a non-constant value to a variable or property that requires a constant.

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