Flutter Excel sheet in the assets folder - dart

Question

I am creating an app in which i will be sending an email with an attached excel sheet.
I already have the excel sheet and my app will be adding some data to the excel sheet before it will be sent.
However after trying to add the excel sheet to my assets folder, adding the path to the pubspec.yaml the File class could not find the file.
pubspec.yaml:
assets:
- logo.png
- Declaratieformulier.xlsx
function:
openFile() {
var bytes = new File("assets/Declaratieformulier.xlsx").readAsBytesSync();
var decoder = new SpreadsheetDecoder.decodeBytes(bytes);
var table = decoder.tables['Blad1'];
I did a little digging and found out assets aren't put on the device as files but are contained within the APK.
So my question is: How do i include an Excel sheet with my app so i can read it and save it as a new Excel file on the phone?

Answer 1

You have to insert the full path in pubspec.yaml so instead of Declaratieformulier.xlsx you have to add assets/Declaratieformulier.xlsx.
assets:
- logo.png
- assets/Declaratieformulier.xlsx
Also you should read the file for the root bundle
import 'package:flutter/services.dart' show ByteData, rootBundle;
...
ByteData data = await rootBundle.load("assets/Declaratieformulier.xlsx");
List<int> bytes = data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);
var decoder = SpreadsheetDecoder.decodeBytes(bytes);

Answer 2

You need to read your file with the Flutter rootBundle.
As #LorenzOliveto said, you also need to fix your pubspec.yaml declaration.
ByteData data = await rootBundle.load("assets/Declaratieformulier.xlsx");
// This would be your equivalent bytes variable
List<int> bytes = data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);
// You can also copy it to the device when the app starts
final directory = await getApplicationDocumentsDirectory();
String filePath = join(directory, "Declaratieformulier.xlsx");
await File(filePath).writeAsBytes(bytes);