【HarmonyOS】鸿蒙应用低功耗蓝牙BLE的使用心得 （二）
一、前言
目前鸿蒙应用的实现逻辑，基本都是参考和移植Android端来实现。针对BLE低功耗蓝牙来说，在鸿蒙化的实现过程中。我们发现了，鸿蒙独有的优秀点，也发现了不一致带来的问题。
并且因为鸿蒙系统还在迭代中，难免有一些bug的存在。目前BLE低功耗蓝牙主流程环节是没有问题的。
鸿蒙整体的实现流程与Android基本是一致。但是在BLE中有一个点需要特别注意。
当周边设备（外围设备）开启广播时，其实没有前置条件，不需要先开启GATT服务器和注册相关服务。但是有些业务逻辑是如此，导致我们开发的时候，惯性思维。实际上鸿蒙BLE在广播流程设计上，并不需要前置条件。
当周边设备持续发送广播，例如智能腕表发送广播，这时候中心设备（中央设备），例如手机才能通过BLE扫描去去识别到该设备。然后才是连接和信息传递的过程。
二、目前已知鸿蒙和Android不一致的实现点梳理：
1.安卓中设置低功耗蓝牙广播，其中有参数可以设置超时时间：
AdvertiseSettings.Builder.SetTimeout()。
但是对标鸿蒙中设置广播，文档中并没有该参数。鸿蒙的低功耗蓝牙广播，无法设置超时时间。
2.鸿蒙中的低功耗蓝牙广播设置对象，ble.AdvertiseSetting中只能设置txPower广播强度。设置广播的模式，对标Android的三个广播模式：
在均衡电源模式下执行蓝牙LE广播:
AdvertiseSettings#ADVERTISE_MODE_BALANCED
在低延迟，高功率模式下执行蓝牙LE广播:
AdvertiseSettings#ADVERTISE_MODE_LOW_LATENCY
在低功耗模式下执行蓝牙LE广播
:AdvertiseSettings#ADVERTISE_MODE_LOW_POWER
鸿蒙这边可以使用interval参数来设置广播频率
ADVERTISE_MODE_LOW_LATENCY（低延迟，广播间隔100ms）对应interval的值为 160
ADVERTISE_MODE_BALANCED（均衡模式，广播间隔250ms）对应interval的值为 400
ADVERTISE_MODE_LOW_POWER（低功耗，广播间隔1s）对应interval的值为 1600
三、BLE低功耗蓝牙DEMO项目示例参考：
此项目实际上是从官方文档基础上进行了扩展。文档所示例的样本代码比较割裂，只是针对API功能的讲解，在不知道BLE完成业务流程的基础上，我们是不清楚如何调用的。所以我们开玩笑的角度说，基本上当你会这个技术点了，官方文档也就能看懂了。
项目整个框架采用管理对象进行BLE功能的封装：
GattServermanager
作为GATT服务器（周边设备）的管理类，实现服务器的初始化和服务的注册。
GattClientManager
作为周边设备客户端管理类，实现链接和数据读写传递。
BleScanManager
作为BLE扫描管理类，实现扫描和结果的处理。
BleAdvertisingManager
作为BLE广播类，实现广播的处理，特征值和描述符的生成。
BLEMgr
作为总管理类，业务逻辑的感知层，业务直接调用BLEMgr实现低功耗蓝牙接口的调用。
Index.ets 启动页
import { CommonTextModifier } from '../common/CommonTextModifier'
import { BLEMgr } from '../mgr/BLEMgr';
import { promptAction } from '@kit.ArkUI';
import { PermissionsUtil } from '../utils/PermissionsUtil';
struct Index { isOpenBluetooth: boolean = false;private mBLEMgr: BLEMgr = new BLEMgr();txtModifier: CommonTextModifier = new CommonTextModifier()async aboutToAppear() {let isHave: boolean = await PermissionsUtil.requestPermission();if(isHave){this.isOpenBluetooth = this.mBLEMgr.getBluetoothState();}else{this.toSysSettingPage();}}private toSysSettingPage(){globalThis.sysContext.startAbility({bundleName: 'com.huawei.hmos.settings',abilityName: 'com.huawei.hmos.settings.MainAbility',// com.huawei.hmos.settings.AppInfoAbilityuri: 'application_info_entry', //application_settings application_info_entryparameters: {pushParams: globalThis.sysContext.abilityInfo.bundleName // 应用包名com.example.tosettingdemo 'uiAbilityContext.abilityInfo.bundleName'}});}onClickStart = async ()=>{let isHave: boolean = await PermissionsUtil.requestPermission();if(isHave){this.mBLEMgr.startBluetooth((str: string)=>{let content: string = "";if (str == 'STATE_ON') {content = "蓝牙已开启";}else{content = "开启错误：" + str;}promptAction.showToast({message: content});});}else{this.toSysSettingPage();}}onClickClose = async ()=>{let isHave: boolean = await PermissionsUtil.requestPermission();if(isHave){this.mBLEMgr.closeBluetooth((str: string)=>{let content: string = "";if (str == 'STATE_OFF') {content = "蓝牙已关闭";}else{content = "关闭错误：" + str;}promptAction.showToast({message: content});});}else{this.toSysSettingPage();}}onClickStartAdv = ()=>{this.mBLEMgr.startAdvertising((advState: string)=>{let content: string = "";if(advState == "STARTED"){content = "广播已开启";}else{content = "广播错误：" + advState;}promptAction.showToast({message: content});});}onClickCloseAdv = ()=>{this.mBLEMgr.stopAdvertising((str: string)=>{promptAction.showToast({message: str});});}onClickStartScan = ()=>{this.mBLEMgr.startScan();}onClickCloseScan = ()=>{this.mBLEMgr.stopScan();}onClickStartServer = ()=>{this.mBLEMgr.registerServer((res: string)=>{promptAction.showToast({message: res});});}onClickCloseServer = ()=>{this.mBLEMgr.unRegisterServer((res: string)=>{promptAction.showToast({message: res});});} LineView(){Line().width("100%").height(px2vp(2)).backgroundColor(Color.Black).margin({top: px2vp(100)})}build() {Column() {Column(){Text(this.isOpenBluetooth ? "蓝牙状态: 已开启" : "蓝牙状态: 已关闭")Text("蓝牙设备名：" + this.mBLEMgr.getCurrentDeviceName())}Text("开启蓝牙").attributeModifier(this.txtModifier).onClick(this.onClickStart)Text("关闭蓝牙").attributeModifier(this.txtModifier).onClick(this.onClickClose)this.LineView()Text("启动服务").attributeModifier(this.txtModifier).onClick(this.onClickStartServer)Text("关闭服务").attributeModifier(this.txtModifier).onClick(this.onClickCloseServer)Text("开启广播").attributeModifier(this.txtModifier).onClick(this.onClickStartAdv)Text("关闭广播").attributeModifier(this.txtModifier).onClick(this.onClickCloseAdv)this.LineView()Text("开启扫描").attributeModifier(this.txtModifier).onClick(this.onClickStartScan)Text("关闭扫描").attributeModifier(this.txtModifier).onClick(this.onClickCloseScan)}.height('100%').width('100%')}
}BLEMgr.ets
import bleAdvertisingManager from "./BleAdvertisingManager";
import bleScanManager from "./BleScanManager";
import { access } from '@kit.ConnectivityKit';
import gattServerManager from "./GattServerManager";
import { connection } from '@kit.ConnectivityKit';
import { BusinessError } from "@kit.BasicServicesKit";const TAG: string = "BLEMgr";export class BLEMgr {public getBluetoothState(): boolean {let state = access.getState();return this.getStateName(state) == "STATE_ON" ? true : false;}/*** 当前设备蓝牙设备名称*/public getCurrentDeviceName(){let localName: string = "";try {localName = connection.getLocalName();console.info(TAG, 'getCurrentDeviceName localName: ' + localName);} catch (err) {console.error(TAG, 'getCurrentDeviceName errCode: ' + (err as BusinessError).code + ', errMessage: ' + (err as BusinessError).message);}return localName;}/*** 蓝牙广播状态* @param state* @returns*/public getAdvState(state: number){switch (state) {case 1:// 首次启动广播后的状态。return 'STARTED';case 2:// 临时启动广播后的状态。return 'ENABLED';case 3:// 临时停止广播后的状态。return 'DISABLED';case 4:// 完全停止广播后的状态。return 'STOPPED';default:return 'unknown status';}}/*** 蓝牙开启状态* @param state* @returns*/private getStateName(state: number): string {switch (state) {case 0:// 蓝牙已关闭。return 'STATE_OFF'; ;case 1:// 蓝牙正在打开。return 'STATE_TURNING_ON';case 2:// 蓝牙已打开。return 'STATE_ON';case 3:// 蓝牙正在关闭。return 'STATE_TURNING_OFF';case 4:// 蓝牙正在打开LE-only模式。return 'STATE_BLE_TURNING_ON';case 5:// 蓝牙正处于LE-only模式。return 'STATE_BLE_ON';case 6:// 蓝牙正在关闭LE-only模式。return 'STATE_BLE_TURNING_OFF';default:return 'unknown status';}}/*** 开启蓝牙*/public startBluetooth(callback: (str: string)=> void){try {access.enableBluetooth();} catch (err) {let errStr: string = JSON.stringify(err);console.info(TAG, 'startBluetooth enableBluetooth err: ' + errStr);callback(errStr);}access.on('stateChange', (data) => {let btStateMessage = this.getStateName(data);callback(btStateMessage);if (btStateMessage == 'STATE_ON') {access.off('stateChange');}console.info('bluetooth statues: ' + btStateMessage);});}/*** 关闭蓝牙*/public closeBluetooth(callback: (str: string)=> void){access.disableBluetooth();access.on('stateChange', (data) => {let btStateMessage = this.getStateName(data);callback(btStateMessage);if (btStateMessage == 'STATE_OFF') {access.off('stateChange');}console.info("bluetooth statues: " + btStateMessage);})}/*** 创建GATT服务器，注册服务*/public registerServer(callBack: (str: string)=> void){gattServerManager.registerServer(callBack);}/*** 删除服务，关闭GATT服务器*/public unRegisterServer(callBack: (str: string)=> void){gattServerManager.unRegisterServer(callBack);}/*** 开启广播*/public async startAdvertising(callBack: (state: string)=> void) {await bleAdvertisingManager.startAdvertising((state: number)=>{let advState: string = this.getAdvState(state);callBack(advState);});}/*** 关闭广播*/public async stopAdvertising(callBack: (str: string)=> void) {await bleAdvertisingManager.stopAdvertising(callBack);}/*** 开始扫描*/public startScan() {bleScanManager.startScan();}/*** 关闭扫描*/public stopScan() {bleScanManager.stopScan();}}
GattServermanager.ets
import { ble } from '@kit.ConnectivityKit';
import { constant } from '@kit.ConnectivityKit';
import { BusinessError } from '@kit.BasicServicesKit';const TAG: string = 'GattServerManager';export class GattServerManager {gattServer: ble.GattServer | undefined = undefined;connectState: ble.ProfileConnectionState = constant.ProfileConnectionState.STATE_DISCONNECTED;myServiceUuid: string = '00001810-0000-1000-8000-00805F9B34FB';myCharacteristicUuid: string = '00001820-0000-1000-8000-00805F9B34FB';myFirstDescriptorUuid: string = '00002902-0000-1000-8000-00805F9B34FB'; // 2902一般用于notification或者indicationmySecondDescriptorUuid: string = '00002903-0000-1000-8000-00805F9B34FB';// 构造BLEDescriptorprivate initDescriptor(des: string, value: ArrayBuffer): ble.BLEDescriptor {let descriptor: ble.BLEDescriptor = {serviceUuid: this.myServiceUuid,characteristicUuid: this.myCharacteristicUuid,descriptorUuid: des,descriptorValue: value};return descriptor;}// 构造BLECharacteristicprivate initCharacteristic(): ble.BLECharacteristic {let descriptors: Array<ble.BLEDescriptor> = [];let descBuffer = new ArrayBuffer(2);let descValue = new Uint8Array(descBuffer);descValue[0] = 31;descValue[1] = 32;descriptors[0] = this.initDescriptor(this.myFirstDescriptorUuid, new ArrayBuffer(2));descriptors[1] = this.initDescriptor(this.mySecondDescriptorUuid, descBuffer);let charBuffer = new ArrayBuffer(2);let charValue = new Uint8Array(charBuffer);charValue[0] = 21;charValue[1] = 22;let characteristic: ble.BLECharacteristic = {serviceUuid: this.myServiceUuid,characteristicUuid: this.myCharacteristicUuid,characteristicValue: charBuffer,descriptors: descriptors};return characteristic;}// 1. 订阅连接状态变化事件public onGattServerStateChange() {if (!this.gattServer) {console.error(TAG, 'no gattServer');return;}try {this.gattServer.on('connectionStateChange', (stateInfo: ble.BLEConnectionChangeState) => {let state = '';switch (stateInfo.state) {case 0:state = 'DISCONNECTED';break;case 1:state = 'CONNECTING';break;case 2:state = 'CONNECTED';break;case 3:state = 'DISCONNECTING';break;default:state = 'undefined';break;}console.info(TAG, 'onGattServerStateChange: device=' + stateInfo.deviceId + ', state=' + state);});} catch (err) {console.error(TAG, 'errCode: ' + (err as BusinessError).code + ', errMessage: ' + (err as BusinessError).message);}}// 2. server端注册服务时调用public registerServer(callBack: (str: string)=> void) {let characteristics: Array<ble.BLECharacteristic> = [];let characteristic = this.initCharacteristic();characteristics.push(characteristic);let gattService: ble.GattService = {serviceUuid: this.myServiceUuid,isPrimary: true,characteristics: characteristics};console.info(TAG, 'registerServer ' + this.myServiceUuid);try {this.gattServer = ble.createGattServer(); // 2.1 构造gattServer，后续的交互都需要使用该实例this.onGattServerStateChange(); // 2.2 订阅连接状态this.gattServer.addService(gattService);callBack("服务成功");} catch (err) {callBack("服务失败：" + JSON.stringify(err));console.error(TAG, 'errCode: ' + (err as BusinessError).code + ', errMessage: ' + (err as BusinessError).message);}}// 3. 订阅来自gattClient的读取特征值请求时调用public onCharacteristicRead() {if (!this.gattServer) {console.error(TAG, 'no gattServer');return;}console.info(TAG, 'onCharacteristicRead');try {this.gattServer.on('characteristicRead', (charReq: ble.CharacteristicReadRequest) => {let deviceId: string = charReq.deviceId;let transId: number = charReq.transId;let offset: number = charReq.offset;console.info(TAG, 'receive characteristicRead');let rspBuffer = new ArrayBuffer(2);let rspValue = new Uint8Array(rspBuffer);rspValue[0] = 21;rspValue[1] = 22;let serverResponse: ble.ServerResponse = {deviceId: deviceId,transId: transId,status: 0, // 0表示成功offset: offset,value: rspBuffer};try {this.gattServer?.sendResponse(serverResponse);} catch (err) {console.error(TAG, 'errCode: ' + (err as BusinessError).code + ', errMessage: ' + (err as BusinessError).message);}});} catch (err) {console.error(TAG, 'errCode: ' + (err as BusinessError).code + ', errMessage: ' + (err as BusinessError).message);}}// 4. 订阅来自gattClient的写入特征值请求时调用public onCharacteristicWrite() {if (!this.gattServer) {console.error(TAG, 'no gattServer');return;}console.info(TAG, 'onCharacteristicWrite');try {this.gattServer.on('characteristicWrite', (charReq: ble.CharacteristicWriteRequest) => {let deviceId: string = charReq.deviceId;let transId: number = charReq.transId;let offset: number = charReq.offset;console.info(TAG, 'receive characteristicWrite: needRsp=' + charReq.needRsp);if (!charReq.needRsp) {return;}let rspBuffer = new ArrayBuffer(0);let serverResponse: ble.ServerResponse = {deviceId: deviceId,transId: transId,status: 0, // 0表示成功offset: offset,value: rspBuffer};try {this.gattServer?.sendResponse(serverResponse);} catch (err) {console.error(TAG, 'errCode: ' + (err as BusinessError).code + ', errMessage: ' + (err as BusinessError).message);}});} catch (err) {console.error(TAG, 'errCode: ' + (err as BusinessError).code + ', errMessage: ' + (err as BusinessError).message);}}// 5. 订阅来自gattClient的读取描述符请求时调用public onDescriptorRead() {if (!this.gattServer) {console.error(TAG, 'no gattServer');return;}console.info(TAG, 'onDescriptorRead');try {this.gattServer.on('descriptorRead', (desReq: ble.DescriptorReadRequest) => {let deviceId: string = desReq.deviceId;let transId: number = desReq.transId;let offset: number = desReq.offset;console.info(TAG, 'receive descriptorRead');let rspBuffer = new ArrayBuffer(2);let rspValue = new Uint8Array(rspBuffer);rspValue[0] = 31;rspValue[1] = 32;let serverResponse: ble.ServerResponse = {deviceId: deviceId,transId: transId,status: 0, // 0表示成功offset: offset,value: rspBuffer};try {this.gattServer?.sendResponse(serverResponse);} catch (err) {console.error(TAG, 'errCode: ' + (err as BusinessError).code + ', errMessage: ' + (err as BusinessError).message);}});} catch (err) {console.error(TAG, 'errCode: ' + (err as BusinessError).code + ', errMessage: ' + (err as BusinessError).message);}}// 6. 订阅来自gattClient的写入描述符请求时调用public onDescriptorWrite() {if (!this.gattServer) {console.error(TAG, 'no gattServer');return;}console.info(TAG, 'onDescriptorWrite');try {this.gattServer.on('descriptorWrite', (desReq: ble.DescriptorWriteRequest) => {let deviceId: string = desReq.deviceId;let transId: number = desReq.transId;let offset: number = desReq.offset;console.info(TAG, 'receive descriptorWrite: needRsp=' + desReq.needRsp);if (!desReq.needRsp) {return;}let rspBuffer = new ArrayBuffer(0);let serverResponse: ble.ServerResponse = {deviceId: deviceId,transId: transId,status: 0, // 0表示成功offset: offset,value: rspBuffer};try {this.gattServer?.sendResponse(serverResponse);} catch (err) {console.error(TAG, 'errCode: ' + (err as BusinessError).code + ', errMessage: ' + (err as BusinessError).message);}});} catch (err) {console.error(TAG, 'errCode: ' + (err as BusinessError).code + ', errMessage: ' + (err as BusinessError).message);}}// 7. server端删除服务，不再使用时调用public unRegisterServer(callBack: (str: string)=> void) {if (!this.gattServer) {console.error(TAG, 'no gattServer');return;}console.info(TAG, 'unRegisterServer ' + this.myServiceUuid);try {this.gattServer.removeService(this.myServiceUuid); // 7.1 删除服务callBack("关闭服务");this.gattServer.off('connectionStateChange', (stateInfo: ble.BLEConnectionChangeState) => { // 7.2 取消订阅连接状态});this.gattServer.close() // 7.3 如果不再使用此gattServer，则需要close} catch (err) {callBack("关闭失败：" + JSON.stringify(err));console.error(TAG, 'errCode: ' + (err as BusinessError).code + ', errMessage: ' + (err as BusinessError).message);}}
}let gattServerManager = new GattServerManager();
export default gattServerManager as GattServerManager;
其余GattClientManager BleScanManager BleAdvertisingManager 类可以参考官方文档。