Flutter Function to reload variable

Issue

I wanted to make like a currency converter so I created this,

final montant = TextEditingController()..text = '500';
double convertEuro(montant) {
  double convtEur = (double.parse(montant.text) / 3.2);
  return convtEur;
}

double converted = 0;

I had a problem with my function here because the function when the screen loads it's null so I created that converted variable ( It's a stupid move I know at least to get rid of the error on my screen but only showing the initial value from my textController above

Text(
    "${double.parse(montant.text)}" +
        "DT = $converted" +
        " €",
 )

Anyway, the function is triggered when a button is pressed.

onPressed: () {
                if (_formKey.currentState.validate()) {
                  converted = convertEuro(montant);
                }
              },

Can anyone help me how to change that variable value and make it change on my screen when the button is pressed?

Solution

You can do like this:

setState(() {
  converted = convertEuro(montant);
});

In this, you're basically doing a rebuild of the widget. Thus to implement this in your code, put setState under the onPress:

onPressed: () {
  if (_formKey.currentState.validate()) {
    setState(() {
      converted = convertEuro(montant);
    });
  }
},

Answered By - Shourya Shikhar