Pass a function in onFocusChange Flutter

Question

I got this function :

void _CalculTotal() {
total = total + double.tryParse(widget.controllers.last.text);
setState(() {
  totalDocument.text = total.toString();
});

}

I want to pass it in onFocusChange when the user loses the focus .

Container(
            width: MediaQuery.of(context).size.width / 3.7,
            color: Color.fromARGB(255, 255, 255, 255),
            child: Focus(
              onFocusChange: (hasFocus) {
                if (!hasFocus) 
               widget.Prix;
              },
              child: TextFormField(
                textInputAction: TextInputAction.done,
                enabled: true,
                controller: widget.fieldController4,
                validator: widget.fieldValidator,
                style: TextStyle(
                  fontSize: 15.0,
                  color: Colors.black,
                ),
                decoration: InputDecoration(
                  contentPadding: EdgeInsets.all(10.0),
                  hintText: "${widget.content4}",
                  hintStyle: TextStyle(
                      color: Color.fromARGB(255, 190, 190, 190),
                      fontSize: 14),
                  fillColor: Color.fromARGB(255, 0, 0, 0),
                ),
              ),
            ),
          ),

this is my widget constructor :

class InputRefNomProduit extends StatefulWidget {

final VoidCallback Prix;
InputRefNomProduit(
  {
      // ...
  this.Prix
  });

and this is where I'm calling the widget in my main screen :

InputRefNomProduit(
      // ..
      Prix: _CalculTotal,
      )

I'm not getting any error but the function won't work .(I tried to print a message when the function is triggered but the message won't show up , so the call wasn't successful). If I put a simple print statement here , It works :

onFocusChange: (hasFocus) {
            if (!hasFocus) 
           print("Hello");
          },

Answer 1

You can do that using a focusNode like this

 FocusNode firstFocusNode = FocusNode();

In your initState add a listener of the focusNode and call function onFocus change

 void initState() {
   super.initState();
   firstFocusNode.addListener(() {
  if (!firstFocusNode.hasFocus) {
      _CalculTotal();
  } 
 });
}
 

Here's the textFormField.

TextFormField(
        focusNode: firstFocusNode,
        onFieldSubmitted: (v) {
          FocusScope.of(context)
              .requestFocus(firstFocusNode);
        }, //your other properties 
 )

Let me know if it works for you.