What is the difference between calling the function without parentheses and with parentheses

Question

What is the difference between calling the function without parentheses and with parentheses on onPressed or Ontap?

I just know that void function can\'t be called with

Answer 1

Here is the difference:

onPressed: _incrementCounter is a reference to an existing function is passed.

This only works if the parameters of the callback expected by onPressed and _incrementCounter are compatible.

onPressed: _incrementCounter() _incrementCounter() is executed and the returned result is passed to onPressed. This is a common mistake when done unintentionally when actually the intention was to pass a reference to _incrementCounter instead of calling it.