Flutter USB打印插件android_usb_printer的使用

Flutter USB打印插件android_usb_printer的使用

android_usb_printer

Flutter Android端插件，提供操作USB打印机的方法能力。

使用方法

1. 添加依赖

   在 pubspec.yaml 文件中添加以下依赖：

   dependencies:
     android_usb_printer: ^0.0.1
   

2. 发送打印字节数组示例

   下面是一个发送打印字节数组的示例代码：

   import 'package:flutter/services.dart';
   import 'package:android_usb_printer/android_usb_printer.dart';
   
   // 假设你已经有了usbDeviceInfo和bytes变量
   var result = await AndroidUsbPrinterPlatform.instance.writeBytes(
       usbDeviceInfo,
       bytes,
   );
   

提供API方法

以下是插件提供的API方法：

/// 获取本地打印机列表
Future<List<UsbDeviceInfo>> queryLocalUsbDevice()

/// 打印机发送字节数据
/// @param singleLimit, 单次最大传输字节长度，内部会将 bytes 按照 singleLimit 阈值进行切割分组后依次 write
Future<int> writeBytes(UsbDeviceInfo usbDeviceInfo, List<int> bytes, {int singleLimit = -1})

/// 接收打印机字节数据
/// @param timeOut, timeOut毫秒内无接收数据直接返回null
Future<Uint8List?> readBytes(UsbDeviceInfo usbDeviceInfo, {int timeOut = 2000})

/// 获取打印机连接状态
Future<bool> checkDeviceConn(UsbDeviceInfo usbDeviceInfo)

/// 打印机连接
Future<bool> connect(UsbDeviceInfo usbDeviceInfo)

/// 打印机断开连接
Future<bool> disconnect(UsbDeviceInfo usbDeviceInfo)

/// 获取打印机设备权限
Future<bool> checkDevicePermission(UsbDeviceInfo usbDeviceInfo)

/// 申请打印机设备权限
Future<bool> requestDevicePermission(UsbDeviceInfo usbDeviceInfo)

/// 删除原生层中 usb conn 缓存（删除设备时可调用）
Future<dynamic> removeUsbConnCache(UsbDeviceInfo usbDeviceInfo)

提供监听USB插拔，USB设备授权能力

通过监听USB插拔事件和USB设备授权事件，你可以实时获取USB设备的状态变化。示例如下：

AndroidUsbPrinterPlatform.instance.usbPlugInfoStream.listen((usbPlugInfo) {
  final usbDeviceInfo = usbPlugInfo.usbDevice; // 插入的USB设备信息，包括 vId, pId, sId
  final plug = usbPlugInfo.plug; // 消息类型枚举（包含状态：拔出、插入、授权成功）
});

UsbPlugInfo 结构如下：

class UsbPlugInfo {
  final UsbPlugInfoEnum plug;
  final UsbDeviceInfo usbDevice;

  UsbPlugInfo(this.usbDevice, this.plug);
}

enum UsbPlugInfoEnum {
  attached, // 插入
  detached, // 拔出
  granted, // 授权成功
}

完整示例Demo

以下是一个完整的示例代码，展示了如何使用该插件：

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

import 'package:flutter/services.dart';
import 'package:android_usb_printer/android_usb_printer.dart';

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

class MyApp extends StatefulWidget {
  const MyApp({super.key});

  [@override](/user/override)
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  String _platformVersion = 'Unknown';
  final _androidUsbPrinterPlugin = AndroidUsbPrinterPlatform.instance;

  [@override](/user/override)
  void initState() {
    super.initState();
    initPlatformState();
  }

  // Platform messages are asynchronous, so we initialize in an async method.
  Future<void> initPlatformState() async {
    String platformVersion;
    // Platform messages may fail, so we use a try/catch PlatformException.
    // We also handle the message potentially returning null.
    try {
      platformVersion = await _androidUsbPrinterPlugin
              .queryLocalUsbDevice()
              .then(
                  (value) => value.map((e) => e.toMap()).toList().toString()) ??
          'Unknown platform version';
    } on PlatformException {
      platformVersion = 'Failed to get platform version.';
    }

    // If the widget was removed from the tree while the asynchronous platform
    // message was in flight, we want to discard the reply rather than calling
    // setState to update our non-existent appearance.
    if (!mounted) return;

    setState(() {
      _platformVersion = platformVersion;
    });
  }

  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Plugin example app'),
        ),
        body: Center(
          child: Text('Running on: $_platformVersion\n'),
        ),
      ),
    );
  }
}