Flutter USB热敏打印机控制插件flutter_usb_thermal_plugin的使用

flutter_usb_thermal_plugin 是一个用于在 Flutter 应用中控制 USB 热敏打印机的插件。它允许你通过 USB 连接发送打印指令到热敏打印机，从而实现打印功能。

安装插件

首先，你需要在 pubspec.yaml 文件中添加 flutter_usb_thermal_plugin 插件的依赖：

dependencies:
  flutter:
    sdk: flutter
  flutter_usb_thermal_plugin: ^latest_version

然后运行 flutter pub get 来安装插件。

基本使用

1. 获取 USB 设备列表

你可以使用 flutter_usb_thermal_plugin 来获取当前连接的 USB 设备列表：

import 'package:flutter_usb_thermal_plugin/flutter_usb_thermal_plugin.dart';

Future<void> getUsbDevices() async {
  List<UsbDevice> devices = await FlutterUsbThermalPlugin.getUsbDevices();
  for (var device in devices) {
    print('Device: ${device.deviceName}, Vendor ID: ${device.vendorId}, Product ID: ${device.productId}');
  }
}

2. 连接打印机

在获取到设备列表后，你可以选择其中一个设备进行连接：

Future<void> connectToPrinter() async {
  List<UsbDevice> devices = await FlutterUsbThermalPlugin.getUsbDevices();
  if (devices.isNotEmpty) {
    UsbDevice printer = devices.first;
    bool isConnected = await FlutterUsbThermalPlugin.connect(printer);
    if (isConnected) {
      print('Connected to printer: ${printer.deviceName}');
    } else {
      print('Failed to connect to printer');
    }
  }
}

3. 发送打印指令

连接成功后，你可以发送打印指令到打印机。通常，热敏打印机使用 ESC/POS 指令集进行控制。你可以使用 flutter_usb_thermal_plugin 提供的 printText 方法来发送文本：

Future<void> printText() async {
  String text = "Hello, World!";
  bool isPrinted = await FlutterUsbThermalPlugin.printText(text);
  if (isPrinted) {
    print('Text printed successfully');
  } else {
    print('Failed to print text');
  }
}

4. 断开连接

打印完成后，记得断开与打印机的连接：

Future<void> disconnectPrinter() async {
  bool isDisconnected = await FlutterUsbThermalPlugin.disconnect();
  if (isDisconnected) {
    print('Disconnected from printer');
  } else {
    print('Failed to disconnect from printer');
  }
}

高级功能

除了基本的文本打印，flutter_usb_thermal_plugin 还支持其他 ESC/POS 指令，例如打印条形码、二维码、图片等。你可以参考插件的文档或源代码来了解更多高级功能。

注意事项

1. 权限：在 Android 上，使用 USB 设备需要获取相应的权限。你需要确保在 AndroidManifest.xml 中添加 USB 权限声明：

   <uses-permission android:name="android.permission.USB_PERMISSION" />
   

2. 设备兼容性：不同的热敏打印机可能支持不同的指令集，因此在开发时需要确保你的打印指令与目标打印机兼容。

3. USB 连接：确保在连接打印机时，设备已通过 USB 正确连接，并且在 Android 设备上已授权访问 USB 设备。

示例代码

以下是一个完整的示例代码，展示了如何使用 flutter_usb_thermal_plugin 连接打印机并打印文本：

import 'package:flutter/material.dart';
import 'package:flutter_usb_thermal_plugin/flutter_usb_thermal_plugin.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
      home: PrinterScreen(),
    );
  }
}

class PrinterScreen extends StatefulWidget {
  [@override](/user/override)
  _PrinterScreenState createState() => _PrinterScreenState();
}

class _PrinterScreenState extends State<PrinterScreen> {
  [@override](/user/override)
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('USB Thermal Printer Example'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            ElevatedButton(
              onPressed: getUsbDevices,
              child: Text('Get USB Devices'),
            ),
            ElevatedButton(
              onPressed: connectToPrinter,
              child: Text('Connect to Printer'),
            ),
            ElevatedButton(
              onPressed: printText,
              child: Text('Print Text'),
            ),
            ElevatedButton(
              onPressed: disconnectPrinter,
              child: Text('Disconnect Printer'),
            ),
          ],
        ),
      ),
    );
  }

  Future<void> getUsbDevices() async {
    List<UsbDevice> devices = await FlutterUsbThermalPlugin.getUsbDevices();
    for (var device in devices) {
      print('Device: ${device.deviceName}, Vendor ID: ${device.vendorId}, Product ID: ${device.productId}');
    }
  }

  Future<void> connectToPrinter() async {
    List<UsbDevice> devices = await FlutterUsbThermalPlugin.getUsbDevices();
    if (devices.isNotEmpty) {
      UsbDevice printer = devices.first;
      bool isConnected = await FlutterUsbThermalPlugin.connect(printer);
      if (isConnected) {
        print('Connected to printer: ${printer.deviceName}');
      } else {
        print('Failed to connect to printer');
      }
    }
  }

  Future<void> printText() async {
    String text = "Hello, World!";
    bool isPrinted = await FlutterUsbThermalPlugin.printText(text);
    if (isPrinted) {
      print('Text printed successfully');
    } else {
      print('Failed to print text');
    }
  }

  Future<void> disconnectPrinter() async {
    bool isDisconnected = await FlutterUsbThermalPlugin.disconnect();
    if (isDisconnected) {
      print('Disconnected from printer');
    } else {
      print('Failed to disconnect from printer');
    }
  }
}