android - 热敏蓝牙打印机在我的颤振应用程序上不起作用

Question

我正在使用包esc_pos_bluetooth: ^0.4.1。当我运行模板应用程序时，它可以正常工作，蓝牙热敏打印机可以正常工作。但是当我在我的应用程序中复制相同的代码时，无法识别打印机。

编码：

class PrinterScreen extends StatefulWidget {
  final Order order;
  PrinterScreen(this.order);
  @override
  _PrinterScreenState createState() => _PrinterScreenState();
}

class _PrinterScreenState extends State<PrinterScreen> {
  PrinterBluetoothManager printerManager = PrinterBluetoothManager();
  List<PrinterBluetooth> _devices = [];

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

    printerManager.scanResults.listen((devices) async {
      print('UI: Devices found ${devices.length}');
      setState(() {
        _devices = devices;
      });
    });
  }

  void _startScanDevices() {
    setState(() {
      _devices = [];
    });
    printerManager.startScan(Duration(seconds: 4));
  }

  void _stopScanDevices() {
    printerManager.stopScan();
  }

  void _testPrint(PrinterBluetooth printer) async {
    printerManager.selectPrinter(printer);

    const PaperSize paper = PaperSize.mm58;
    final profile = await CapabilityProfile.load();

    final PosPrintResult res =
        await printerManager.printTicket((await demoReceipt(paper, profile)));

    print(res.msg);
  }

  Future<List<int>> demoReceipt(
      PaperSize paper, CapabilityProfile profile) async {
    final Generator ticket = Generator(paper, profile);
    List<int> bytes = [];

    bytes += ticket.text('My name');
    bytes += ticket.text('is');
    bytes += ticket.text('Eric');
    bytes += ticket.text(DateTime.now().toString());
    bytes += ticket.text('Slide to the left');

    ticket.cut();
    return bytes;
  }


  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Printer page'),
      ),
      body: ListView.builder(
          itemCount: _devices.length,
          itemBuilder: (BuildContext context, int index) {
            return InkWell(
              onTap: () => _testPrint(_devices[index]),
              child: Column(
                children: <Widget>[
                  Container(
                    height: 60,
                    padding: EdgeInsets.only(left: 10),
                    alignment: Alignment.centerLeft,
                    child: Row(
                      children: <Widget>[
                        Icon(Icons.print),
                        SizedBox(width: 10),
                        Expanded(
                          child: Column(
                            crossAxisAlignment: CrossAxisAlignment.start,
                            mainAxisAlignment: MainAxisAlignment.center,
                            children: <Widget>[
                              Text(_devices[index].name ?? ''),
                              Text(_devices[index].address),
                              Text(
                                'Click to print a test receipt',
                                style: TextStyle(color: Colors.grey[700]),
                              ),
                            ],
                          ),
                        )
                      ],
                    ),
                  ),
                  Divider(),
                ],
              ),
            );
          }),
      floatingActionButton: StreamBuilder<bool>(
        stream: printerManager.isScanningStream,
        initialData: false,
        builder: (c, snapshot) {
          if (snapshot.data) {
            return FloatingActionButton(
              child: Icon(Icons.stop),
              onPressed: _stopScanDevices,
              backgroundColor: Colors.red,
            );
          } else {
            return FloatingActionButton(
              child: Icon(Icons.search),
              onPressed: _startScanDevices,
            );
          }
        },
      ),
    );
  }
}

套餐：

  flutter_bluetooth_basic: ^0.1.7
  esc_pos_bluetooth: ^0.4.1
  esc_pos_utils: ^1.1.0

颤振版本：2.5.3

安卓清单：

  <uses-permission android:name="android.permission.BLUETOOTH" />
  <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
  <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />

模板应用：

我的应用程序：

标签： androidflutterbluetooththermal-printer