在Flutter应用中，我有一个rxDart块，该块从API服务器获取JSON字符串并将其转换为类列表（销售）。

除了在ListView小部件上显示数据外，我还想使用软件包pdf: 1.3.23打印数据。

pdf程序包具有一个生成器，但不会使用ListView，因此我需要将Sales列表转换为List>，以便将其传递给Table.fromTextArray。

或更笼统地说，如何从已解析的API响应中创建pdf？或者，如何从数据创建pdf？在显示数据之后，从颤动屏幕打印数据必须是第二个最常见的要求，但是我看不出如何解决该问题的线索。

当我尝试将SalesResponse对象传递给Table.fromTextArray时，会收到此消息。

  

不能将参数类型“ SalesResponse”分配给该参数   类型List >。

到目前为止，这是我的代码：

销售模式：

class Sale {
  int _id;
  int _billId;
  String _item;
  int _qty;
  double _price;

  Sale(sale) {
    _id = sale['id'];
    _billId = sale['bill_id'];
    _item = sale['item'];
    _qty = sale['qty'];
    _price = (sale['price'] as num).toDouble();
  }

  int get id => _id;
  int get billId => _billId;
  String get item => _item;
  int get qty => _qty;
  double get price => _price;
}

这是我的销售响应模型

import 'package:exactpos_mobile/model/sale.dart';

class SalesResponse {
  List<Sale> _sales = [];
  String error;

  SalesResponse.fromJson(Map<String,dynamic> parsedJson) {
    print(parsedJson);
    List<Sale> temp = [];
    if (parsedJson['sales'] != null) {
      for (int i = 0; i < parsedJson['sales'].length; i++) {
        Sale _sale = Sale(parsedJson['sales'][i]);
        temp.add(_sale);
      }
      _sales = temp;    
    }
  }

  SalesResponse.withError(String errorValue)
      : _sales = List(),error = errorValue;

  List<Sale> get sales => _sales;
}

销售库

class SaleRepository{
  ApiProvider _apiProvider = ApiProvider();

  Future<SalesResponse> getSales(int billId){
    return _apiProvider.getSales(billId);
  }
}

销售集团

import 'package:rxdart/rxdart.dart';

class SalesBloc {
  final SaleRepository _repository = SaleRepository();
  final PublishSubject<SalesResponse> _subject = PublishSubject<SalesResponse>();
  getSales(int billId) async {
    SalesResponse response = await _repository.getSales(billId); 
    _subject.sink.add(response);
  }
  void dispose() async{
    await _subject.drain();
    _subject.close();
  }
  PublishSubject<SalesResponse> get subject => _subject;
}
final salesBloc = SalesBloc();

这是我的小部件屏幕

SalesResponse salesList;

class SalesScreen extends StatefulWidget {

  static const routeName = '/sales';

  final Bill bill;
  final Tbl table;

  SalesScreen({    
    Key key,@required this.table,@required this.bill
   }) : super(key: key);

  @override
  State<StatefulWidget> createState() => SalesScreenState();      
}

class SalesScreenState extends State<SalesScreen> {

  @override
  void initState() {
    super.initState();

    salesBloc.getSales(widget.bill.id);

    salesList = salesBloc.getSales(widget.bill.id); 

      print('hello');
      print(salesList.sales);
      print('hello');
  }

  @override
  void dispose() {
    salesBloc.dispose();
    super.dispose();
  }
    @override
    Widget build(BuildContext context) {
    return Scaffold(
              drawer: AppDrawer(),appBar: AppBar(
                        backgroundColor: Colors.blue,automaticallyImplyLeading: false,centerTitle : true,title: Text(widget.bill.billNumber.toString(),style: TextStyle(color: Colors.white)
                                    ),leading: IconButton(icon:Icon(Icons.arrow_back),onpressed:() =>
                        Navigator.of(context).pushAndRemoveUntil(
                          MaterialPageRoute(
                             builder: (context) =>
                               BillsScreen(table: widget.table)),(Route<dynamic> route) => false)
                        )
              ),body: SafeArea(
                child: Container(
                       child: 
                          StreamBuilder<SalesResponse>(
                              stream: salesBloc.subject.stream,builder: (context,Asyncsnapshot<SalesResponse> snapshot) {
                                     if (snapshot.hasData) {
                                        if (snapshot.data.error != null && snapshot.data.error.length > 0) {
                                           return _buildErrorWidget(snapshot.data.error);
                                        }
                                        return _buildSalesListWidget(snapshot.data);
                                     } 
                              },)
              ),),floatingactionButtonLocation: FloatingactionButtonLocation.centerDocked,floatingactionButton: Padding(
                    padding: const EdgeInsets.all(8.0),child: Row(
                              mainAxisAlignment: MainAxisAlignment.spaceEvenly,children: <Widget>[

                                 FloatingactionButton(
                                    heroTag: 1,backgroundColor: Colors.yellow,onpressed: () {
                                        Printing.layoutPdf(onLayout:(format)=> 
                                           buildReceipt(widget.table,widget.bill,salesList));
                                    },child: Icon(FontAwesomeIcons.print),],)

    );

  }

  Widget _buildSalesListWidget(SalesResponse data) {

          return ListView.builder(            
                     itemCount: data.sales.length,itemBuilder: (context,index) {

                         return ListTile(                                             
                                  title: Text(                                            
                                              data.sales[index].item,style: TextStyle(
                                                         fontWeight: FontWeight.w500,fontSize: 20,subtitle: Text('qty' + ' ' + data.sales[index].qty.toString() + ',' + 'price' + ' ' + data.sales[index].price.toStringAsFixed(2)),leading: Icon(
                                                FontAwesomeIcons.beer,color: Colors.blue[500],onTap: () {},);
                     },);
  }
 }

最后，我的pdf代码

Future<List<int>> buildReceipt(Tbl table,Bill bill,SalesResponse salesList)  async {

  const PdfPageFormat format = PdfPageFormat(160,900);

  final Document pdf = Document();

    pdf.addPage(MultiPage(

      pageFormat: format,//  PdfPageFormat.a4.copyWith(marginBottom: 1.5 * PdfPageFormat.cm),crossAxisAlignment: CrossAxisAlignment.start,header: (Context context) {

        if (context.pageNumber == 1) {
          return null;
        }

        return Container(

            alignment: Alignment.centerRight,margin: const EdgeInsets.only(top: 3.0 * PdfPageFormat.mm),padding: const EdgeInsets.only(bottom: 3.0 * PdfPageFormat.mm),decoration: const BoxDecoration(
                border:
                    BoxBorder(bottom: true,width: 0.5,color: PdfColors.grey)),child: Text('Exact POS',style: Theme.of(context)
                    .defaultTextStyle
                    .copyWith(color: PdfColors.grey)));
      },footer: (Context context) {
        return Container(
            alignment: Alignment.centerRight,margin: const EdgeInsets.only(top: 1.0 * PdfPageFormat.cm),child: Text('Page ${context.pageNumber} of ${context.pagesCount}',build: (Context context) => <Widget>[
            Header(
                level: 0,child: Row(
                    mainAxisAlignment: MainAxisAlignment.spaceBetween,children: <Widget>[
                      Text('Exact POS',textScaleFactor: 2),PdfLogo()
                    ]
                )
            ),Padding(padding: const EdgeInsets.all(4)),Paragraph(text: table.number),Table.fromTextArray(context: context,data: salesList  ),]
    )
  );
  return pdf.save();
}