tipe 'Future <Uint8List>' bukan subtipe dari tipe 'Widget'

Question

Saya mencoba menampilkan pdf menggunakan tombol ini di aplikasi flutter saya tetapi saya terus mendapatkan kesalahan pada judul

  AppButton.buildAppButton(
                  context,
                  AppButtonType.TEXT_OUTLINE,
                  'Generate PDF',
                  Dimens.BUTTON_BOTTOM_DIMENS, onPressed: () {
                Sheets.showAppHeightEightSheet(
                context: context,
                  widget: work(),
                );
              })

Ini adalah widget pekerjaan saya

      Widget work() {
       dynamic pdf =  generateInvoice(PdfPageFormat.a4);
       return pdf;
     }

yang memanggil fungsi ini. Namun saya tetap mendapatkan jenis kesalahan judul 'Masa Depan' bukan jenis subtipe 'Widget'. Setiap bantuan dihargai. tujuan akhirnya adalah untuk melihat pdf tapi saya tidak yakin bagaimana cara sampai ke sana. Terima kasih!

Future<Uint8List> generateInvoice(PdfPageFormat pageFormat) async {
  final lorem = pw.LoremText();

  final products = <Product>[
    Product('19874', lorem.sentence(4), 3.99, 2),
    Product('98452', lorem.sentence(6), 15, 2),
    Product('28375', lorem.sentence(4), 6.95, 3),
    Product('95673', lorem.sentence(3), 49.99, 4),
    Product('23763', lorem.sentence(2), 560.03, 1),
    Product('55209', lorem.sentence(5), 26, 1),
    Product('09853', lorem.sentence(5), 26, 1),
   
  ];

  final invoice = Invoice(
    invoiceNumber: '982347',
    products: products,
    customerName: 'Abraham Swearegin',
    customerAddress: '54 rue de Rivoli\n75001 Paris, France',
    paymentInfo:
        '4509 Wiseman Street\nKnoxville, Tennessee(TN), 37929\n865-372-0425',
    tax: .15,
    baseColor: PdfColors.teal,
    accentColor: PdfColors.blueGrey900,
  );

  return await invoice.buildPdf(pageFormat);
}

class Invoice {
  Invoice({
    this.products,
    this.customerName,
    this.customerAddress,
    this.invoiceNumber,
    this.tax,
    this.paymentInfo,
    this.baseColor,
    this.accentColor,
  });

  final List<Product> products;
  final String customerName;
  final String customerAddress;
  final String invoiceNumber;


  static const _darkColor = PdfColors.blueGrey800;
  static const _lightColor = PdfColors.white;

  PdfColor get _baseTextColor =>
      baseColor.luminance < 0.5 ? _lightColor : _darkColor;

  PdfColor get _accentTextColor =>
      baseColor.luminance < 0.5 ? _lightColor : _darkColor;

  double get _total =>
      products.map<double>((p) => p.total).reduce((a, b) => a + b);

  double get _grandTotal => _total * (1 + tax);

  PdfImage _logo;

  Future<Uint8List> buildPdf(PdfPageFormat pageFormat) async {
    // Create a PDF document.
    final doc = pw.Document();

    final font1 = await rootBundle.load('assets/roboto1.ttf');
    final font2 = await rootBundle.load('assets/roboto2.ttf');
    final font3 = await rootBundle.load('assets/roboto3.ttf');

    _logo = PdfImage.file(
      doc.document,
      bytes: (await rootBundle.load('assets/logo.png')).buffer.asUint8List(),
    );

    // Add page to the PDF
    doc.addPage(
      pw.MultiPage(
        pageTheme: _buildTheme(
          pageFormat,
          font1 != null ? pw.Font.ttf(font1) : null,
          font2 != null ? pw.Font.ttf(font2) : null,
          font3 != null ? pw.Font.ttf(font3) : null,
        ),
        header: _buildHeader,
        footer: _buildFooter,
        build: (context) => [
          _contentHeader(context),
          _contentTable(context),
          pw.SizedBox(height: 20),
          _contentFooter(context),
          pw.SizedBox(height: 20),
          _termsAndConditions(context),
        ],
      ),
    );

    // Return the PDF file content
    return doc.save();
  }

EDIT :: Saya mencoba melakukan ini sekarang tetapi saya mendapatkan garis bawah merah di bawah baris komentar

   class MyWidget extends StatelessWidget {
  @override
  Widget build(context) {
    return FutureBuilder<Uint8List>(
        future:  generateInvoice(PdfPageFormat.a4),
        builder: (context, AsyncSnapshot<Uint8List> snapshot) {
          if (snapshot.hasData) {
            return snapshot.data;  //get a red underline here
          } else {
            return CircularProgressIndicator();
          }
        }
    );
  }
}

Answer 1

Fungsi kerja Anda akan terlihat seperti ini. Berikut dua paket tambahan yang telah saya gunakan. Untuk menampilkan pdf flutter_pdfview dan menyimpan pdf sementara path_provider .

Future<Widget> work() async{
       Uint8List pdf = await generateInvoice(PdfPageFormat.a4);
       File file = await getPdf(pdf);
       return PDFView(
          filePath: file.path,
          autoSpacing: false,
          pageFling: false,
        );
     }

DIEDIT:

Future<File> getPdf(Uint8List pdf) async{
    Directory output = await getTemporaryDirectory();
    file = File(output.path+"/name_of_the_pdf.pdf");
    await file.writeAsBytes(pdf);
    return file;
  }

Sekarang perbarui metode build Anda sebagai

@override
  Widget build(context) {
    return FutureBuilder<Widget>(
        future:  work(),
        builder: (BuildContext context, AsyncSnapshot<Widget> snapshot) {
          if (snapshot.hasData) {
            return snapshot.data;  //get a red underline here
          } else {
            return CircularProgressIndicator();
          }
        }
    );
  }