扩展外设管理开发指导

场景介绍

扩展外设主要是指通过物理接口连入主设备的配件设备，如手写板、打印机和扫描仪等。应用通过扩展外设管理能力可以查询绑定扩展外设，从而使用扩展外设驱动提供的定制能力来使用扩展外设，如打印机的配套软件。

扩展外设支持Tablet和特定设备上使用。

接口说明

扩展外设管理主要提供的功能有：查询扩展外设列表、绑定和解绑查询到的设备。

扩展外设管理开放能力如下，具体请查阅API参考文档。

表1 扩展外设管理开放能力接口

开发步骤

应用可通过查询绑定扩展外设，从而使用扩展外设的定制驱动能力。开发示例如下：

1. 查询设备列表。

   import deviceManager from '@ohos.driver.deviceManager';
   import { BusinessError } from '@ohos.base';
   
   let matchDevice : deviceManager.USBDevice | null = null;
   try {
     let devices : Array<deviceManager.Device> = deviceManager.queryDevices(deviceManager.BusType.USB);
     for (let item of devices) {
       let device : deviceManager.USBDevice = item as deviceManager.USBDevice;
       // 通过productId和vendorId来匹配要使用的USB设备
       if (device.productId == 1234 && device.vendorId === 2345) {
         matchDevice = device;
         break;
       }
     }
   } catch (error) {
     let errCode = (error as BusinessError).code;
     let message = (error as BusinessError).message;
     console.error(`Failed to query device. Code is ${errCode}, message is ${message}`);
   }
   if (!matchDevice) {
     console.error('No match device');
   }
   

2. 绑定相应的设备。

   import deviceManager from '@ohos.driver.deviceManager';
   import { BusinessError } from '@ohos.base';
   import rpc from '@ohos.rpc';
   
   interface DataType {
     deviceId : number;
     remote : rpc.IRemoteObject;
   }
   
   let remoteObject : rpc.IRemoteObject | null = null;
   try {
     // 12345678为示例deviceId，应用开发时可以通过queryDevices查询到相应设备的deviceId作为入参
     deviceManager.bindDevice(12345678, (error : BusinessError, data : number) => {
       console.error('Device is disconnected');
     }, (error : BusinessError, data : DataType) => {
       if (error) {
         console.error(`bindDevice async fail. Code is ${error.code}, message is ${error.message}`);
         return;
       }
     console.info('bindDevice success');
     remoteObject = data.remote;
     });
   } catch (error) {
     let errCode = (error as BusinessError).code;
     let message = (error as BusinessError).message;
     console.error(`bindDevice fail. Code is ${errCode}, message is ${message}`);
   }
   if (!remoteObject) {
     console.error('Bind device failed');
   }
   

3. 绑定成功后使用设备驱动能力。

   import { BusinessError } from '@ohos.base';
   import rpc from '@ohos.rpc';
   
   let option : rpc.MessageOption = new rpc.MessageOption();
   let data : rpc.MessageSequence = rpc.MessageSequence.create();
   let reply : rpc.MessageSequence = rpc.MessageSequence.create();
   data.writeString('hello');
   let code = 1;
   // remoteObject应用可以通过绑定设备获取到
   let remoteObject : rpc.IRemoteObject | null = null;
   // code和data内容取决于驱动提供的接口
   if (remoteObject != null) {
     (remoteObject as rpc.IRemoteObject).sendMessageRequest(code, data, reply, option)
       .then(() => {
         console.info('sendMessageRequest finish.');
       }).catch((error : BusinessError) => {
         let errCode = (error as BusinessError).code;
         console.error('sendMessageRequest fail. code:' + errCode);
       });
   }
   

4. 设备使用完成，解绑设备。

   import deviceManager from '@ohos.driver.deviceManager';
   import { BusinessError } from '@ohos.base';
   
   try {
     // 12345678为示例deviceId，应用开发时可以通过queryDevices查询到相应设备的deviceId作为入参
     deviceManager.unbindDevice(12345678, (error : BusinessError, data : number) => {
       if (error) {
         let errCode = (error as BusinessError).code;
         let message = (error as BusinessError).message;
         console.error(`unbindDevice async fail. Code is ${errCode}, message is ${message}`);
         return;
       }
       console.info(`unbindDevice success`);
   });
   } catch (error) {
     let errCode = (error as BusinessError).code;
     let message = (error as BusinessError).message;
     console.error(`unbindDevice fail. Code is ${errCode}, message is ${message}`);
   }