This is the program I have running:

• I have an app that is a single page.
• The page’s widgets are defined in separate files.
• I have data that comes from the serial port and data that is entered in a form widget.
• The button widget that calls the function to write the data to the file is in a separate widget from the form widget (for layout reasons and because I’m taking data from the form and the serial buffer).
• I’m using Riverpod to manage the serial data.
  -the Serial data gets passed as a List<List> tofile write function when the button is pressed.

onPressed: () {
   if (ref.watch(serDataProvider).isNotEmpty) {
      // Write the data to a file
      writeFile(ref.watch(serDataProvider));
   }
},

-the write file function is just formatting the data as a .csv file so that it comes up in Excel nicely, and in a way that I can easily select the data create a chart and copy/paste readymade titles.
-With hardcoded form data in the file write function, everything works perfectly.

I’m trying to get the form data to the function when the button is pressed.

• I already have the form created and their contents go into controllers. They work, I can print out the values locally in the form widget.

I tried creating a provider for a data class that holds it:

class Data {
  late String? temperature;
  late String? humidity;

  Data(
      this.temperature,
      this.humidity,

  factory Data.initial() {
    return Data();
  }
}

@riverpod
class FormData extends _$FormData {
  @override
  Data build() {
    return Data.initial();
  }
}

I added the data to the provider in the TextFields like this:

onChanged: (text) {
          ref.read(formDataProvider).temperature = text;
});

I added the form data to the button (function receiving FormData as the datatype) like this:

onPressed: () {
   if (ref.watch(serDataProvider).isNotEmpty) {
      // Write the data to a file
      writeFile(ref.watch(formDataProvider), ref.watch(serDataProvider));
   }
},

In the function, I

void writeFile(Data formData, List<List> listOfSamples) async {
.
. // other code
.
sink.write(‘Temperature: ${formData.temperature}n’);
.
. // other code
.
}

It wasn’t throwing any errors, but I ended up with null (as text) in the file wherever stuff from the form was printed.

I tried passing the form data to the provider in functions a number of different ways, and got the same result.

Looking at the Riverpod page, it states:

*They are not meant to be used for local widget state, such as for:

-storing form state
-currently selected item
-animations
–generally everything that Flutter deals with a “controller” (e.g. TextEditingController)*

So, it appears that my approach is maybe not a good one. If that is the case, what are some good ways of getting the form data to my function?