Error in dart pdf generation

receiptbuilder.dart

import 'dart:typed_data';
import 'models/reciept.dart';
import 'package:flutter/material.dart';
import 'package:pdf/pdf.dart';
import 'models/user.dart';
import 'package:pdf/widgets.dart' as pw;
import 'package:printing/printing.dart';
import 'dart:io';

class ReceiptBuilder {


  User user;
  Receipt _receipt;

  bool _regenerate;
  var rcptId;


  ReceiptBuilder({regenerate,receipt}):_regenerate=regenerate,_receipt=receipt;

  Widget getPdfPreview(double width, double height) {

    return Scaffold(
      appBar: AppBar(
        title: Text("View Receipt Preview"),
      ),
      body: PdfPreview(
        pdfFileName:
            "${this._receipt == null ? "rcpt_1 " : "rcpt_${this._receipt.id}_${this._receipt.date}"}",
        allowPrinting: false,
        canChangePageFormat: false,
        actions: [
          PdfPreviewAction(
              icon: Icon(Icons.email),
              onPressed: (context, __, ___) {
                sendEmail(context);
              })
        ],
        build: (pageFormat) => buildReceiptPdf(pageFormat, width, height,this._receipt),
      ),
    );
  }

  void sendEmail(BuildContext context) {
    // TODO Send email to client directly
  }


  Future<Uint8List> buildReceiptPdf(
      PdfPageFormat pageFormat, double width, double height, Receipt receipt) async {
    final document = pw.Document();
    pw.RichText.debug = false;
    user = await User.getUserFromDatabase();
    rcptId = await Receipt.getLatestId();
    if(!_regenerate)
      Receipt.insertReceipt(receipt);


    document.addPage(pw.Page(
        pageFormat: PdfPageFormat(width, height),
        build: (context) {
          return pw.Padding(
              padding: pw.EdgeInsets.all(8.0),
              child:pw.Stack(
                children: [
                  pw.Container(
                      height: height,
                      width: width,
                      alignment: pw.Alignment.center,

                      child:pw.Opacity(
                          opacity: 0.30,
                          child: pw.Container(
                              width: 200,height: 200,
                              decoration: pw.BoxDecoration(
                                shape: pw.BoxShape.circle,

                              ),
                              child: pw.Image(
                                  PdfImage.file(context.document,
                                      bytes: File(user.logoImagePath).readAsBytesSync()),
                                  fit: pw.BoxFit.contain)
                          )
                      )

                  ),
                  pw.Column(
                      children: [
                        _buildHeader(context,receipt),
                        _receiptContent(context,receipt),
                        pw.SizedBox(height: 40),
                      ]),
                  _buildFooter(context,receipt)
                ]
              )
              );
        }));

    return document.save();
  }

  pw.Widget _buildHeader(pw.Context context,Receipt receipt) {
    return pw.Padding(
        padding: pw.EdgeInsets.all(8.0),
        child: pw.Column(
          children: [
            pw.Row(
                mainAxisAlignment: pw.MainAxisAlignment.spaceBetween,
                children: [
                  pw.Column(
                      crossAxisAlignment: pw.CrossAxisAlignment.start,
                      children: [
                        pw.Text(
                            "${(user == null || user.companyName == null) ? "CompanyName" : "${user.companyName}"}",
                            style: pw.TextStyle(fontSize: 14)),
                        pw.Text(
                            "${(user == null || user.address == null) ? "Address" : "${user.address}"}",
                            maxLines: 2,
                            style: pw.TextStyle(fontSize: 14)),
                        pw.Text(
                            "${(user == null || user.email == null) ? "Email" : "${user.email}"}",
                            style: pw.TextStyle(fontSize: 14)),
                        pw.Text(
                            "${(user == null || user.phoneNo == null) ? "PhoneNo" : "${user.phoneNo}"}",
                            style: pw.TextStyle(fontSize: 14)),
                        (user == null || user.website == null)?null:pw.Text(
                             "${user.website}",
                            style: pw.TextStyle(fontSize: 14))
                      ]),
                  pw.Column(
                      mainAxisAlignment: pw.MainAxisAlignment.start,
                      crossAxisAlignment: pw.CrossAxisAlignment.end,
                      children: [
                        pw.Text("RECEIPT",
                            style: pw.TextStyle(
                                fontWeight: pw.FontWeight.bold, fontSize: 22)),
                        pw.Text(
                            "${rcptId == null ? "Receipt No:1" : "Receipt No:$rcptId"}",
                            style: pw.TextStyle(fontSize: 16)),
                        pw.Text(
                            "${receipt.date == null ? "Date" : "${receipt.date}"}",
                            style: pw.TextStyle(fontSize: 16)),
                      ])
                ]),
            pw.SizedBox(height: 10),
            pw.Divider(),
          ],
        ));
  }

  pw.Widget _buildFooter(pw.Context context,Receipt receipt) {
    // debugPrint("Inside buildFooter");
    // debugPrint("${receipt.date}");

    return pw.Padding(
        padding: pw.EdgeInsets.all(8.0),
        child: pw.Column(
            mainAxisAlignment: pw.MainAxisAlignment.end,
            children: [
              pw.Row(
                  mainAxisAlignment: pw.MainAxisAlignment.spaceBetween,
                  children: [
                    pw.Column(
                        crossAxisAlignment: pw.CrossAxisAlignment.start,
                        children: [
                          pw.Text("Thank you for your payment against "),
                          pw.Text(
                              "${receipt.forInvoice == null ? "LumpSum" : "Invoice No: ${receipt.forInvoice}"}"),
                          pw.SizedBox(height: 40),
                        ]),
                    pw.SizedBox(height: 40),
                    pw.Column(
                        crossAxisAlignment: pw.CrossAxisAlignment.end,
                        children: [
                          pw.Container(
                              width: 100,
                              height: 50,
                              child: user.signImagePath == null
                                  ? pw.Text("Signature")
                                  : pw.Image(
                                  PdfImage.file(context.document,
                                      bytes: File(user.signImagePath).readAsBytesSync()),
                                  fit: pw.BoxFit.fill)),
                          pw.SizedBox(height: 5),
                          pw.Text(user.userName==null?"SenderName":"${user.userName}"),
                          pw.SizedBox(height: 40),
                          // _promotionFooter(context)
                        ]),
                  ]),
              pw.Padding(padding: pw.EdgeInsets.all(8.0))
            ]));
  }

  pw.Widget _receiptContent(pw.Context context, Receipt receipt) {

      return pw.Padding(
          padding: pw.EdgeInsets.all(8.0),
          child: pw.Row(
              mainAxisAlignment: pw.MainAxisAlignment.spaceBetween,
              children: [
                pw.Column(
                    crossAxisAlignment: pw.CrossAxisAlignment.start,
                    children: [
                      pw.Text("Received From:",
                          style: pw.TextStyle(fontSize: 16)),
                      pw.SizedBox(height: 5),
                      pw.Text(
                          "${receipt.fromName == null ? "Customer Name here" : receipt.fromName}",
                          style: pw.TextStyle(
                              fontSize: 14, fontWeight: pw.FontWeight.bold))
                    ]),
                pw.Text(
                    "${receipt.amount == null ? "Amount in Rs" : "Rs ${receipt.amount}"}",
                    style: pw.TextStyle(fontSize: 20))
              ]))
    ;
  }

// pw.Widget _promotionFooter(pw.Context context) {
//   return pw.Row(
//       mainAxisAlignment: pw.MainAxisAlignment.center,
//       children: [
//         pw.Text("PDF generated by Mr Invoice for Mr Mukund Thakkar",
//             style: pw.TextStyle(fontStyle: pw.FontStyle.italic))
//       ]
//   );
// }
}