Flutter USB Printer控制插件drago_usb_printer的使用

drago_usb_printer 是一个用于在Android设备上与USB打印机进行通信的Flutter插件。通过该插件，您可以发送数据并控制USB打印机。本文将介绍如何安装和使用这个插件。

安装

首先，在您的 pubspec.yaml 文件中添加 drago_usb_printer 依赖：

dependencies:
  flutter:
    sdk: flutter
  drago_usb_printer: ^latest_version

然后运行以下命令来安装插件：

flutter pub get

使用示例

获取USB设备列表

要获取连接到设备的所有USB打印机，请调用 getUSBDeviceList() 方法：

_getDevicelist() async {
  List<Map<String, dynamic>> results = [];
  results = await DragoUsbPrinter.getUSBDeviceList();

  print(" length: ${results.length}");
  setState(() {
    devices = results;
  });
}

连接到USB打印机

使用 connect(vendorId, productId) 方法连接到特定的USB打印机：

_connect(int vendorId, int productId) async {
  bool returned;
  try {
    returned = await DragoUsbPrinter.connect(vendorId, productId);
  } on PlatformException {
    // Handle exception here
  }
  if (returned) {
    setState(() {
      connected = true;
    });
  }
}

打印数据

一旦连接成功，您可以使用 write(data) 方法向打印机发送数据：

_print() async {
  try {
    var data = Uint8List.fromList(
        utf8.encode(" Hello world Testing ESC POS printer..."));
    await DragoUsbPrinter.write(data);
  } on PlatformException {
    // Handle exception here
  }
}

完整示例代码

下面是一个完整的示例应用，展示了如何列出所有USB设备，并允许用户选择一个设备进行打印：

import 'dart:convert';
import 'package:drago_usb_printer/drago_usb_printer.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

void main() => runApp(MyApp());

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  List<Map<String, dynamic>> devices = [];
  DragoUsbPrinter dragoUsbPrinter = DragoUsbPrinter();

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

  _getDevicelist() async {
    List<Map<String, dynamic>> results = [];
    results = await DragoUsbPrinter.getUSBDeviceList();

    print(" length: ${results.length}");
    setState(() {
      devices = results;
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('USB PRINTER'),
          actions: <Widget>[
            IconButton(
                icon: Icon(Icons.refresh),
                onPressed: () => _getDevicelist()),
          ],
        ),
        body: devices.isNotEmpty
            ? ListView(
                scrollDirection: Axis.vertical,
                children: _buildList(devices),
              )
            : Center(child: Text("No Devices Found")),
      ),
    );
  }

  List<Widget> _buildList(List<Map<String, dynamic>> devices) {
    return devices.map((device) => ListTile(
      leading: Icon(Icons.usb),
      title: Text(device['manufacturer'] + " " + device['productName']),
      subtitle: Text(device['vendorId'] + " " + device['productId']),
      trailing: IconButton(
        icon: Icon(Icons.print),
        onPressed: () async {
          int vendorId = int.parse(device['vendorId']);
          int productId = int.parse(device['productId']);
          bool? isConnected = await dragoUsbPrinter.connect(vendorId, productId);
          if (isConnected ?? false) {
            var data = Uint8List.fromList(utf8.encode("Hello world Testing ESC POS printer..."));
            await dragoUsbPrinter.write(data);
            await dragoUsbPrinter.close();
          }
        },
      ),
    )).toList();
  }
}

这个示例应用程序展示了如何扫描可用的USB设备、连接到选定的打印机，并发送简单的文本数据以供打印。请根据实际需求调整代码中的参数和逻辑。