OpenHarmony BLE低功耗蓝牙 原创 精华

作者：徐金生
目标：实现BLE蓝牙设备与DAYU200设备之间数据交互，即中心设备接收外围设备的通知数据，OpenHarmony社区提供了详细的API文档，可以移步到：蓝牙

之前在HarmonyOS系统上实现了BLE蓝牙的连接与数据传输，《HarmonyOS BLE蓝牙通信开发总结》，现在需要在OpenHarmony上也实现BLE蓝牙的通信。

设备与环境

设备：BLE蓝牙设备、DAYU200设备
系统：OpenHarmony 3.2 beta1
SDK：9

先看下效果

查看视频

说在前面的话

如果你需要了解蓝牙的基础知识，可以查看《HarmonyOS BLE蓝牙通信开发总结》这篇文章的“蓝牙介绍”部分。

前置步骤

创建项目

说明：创建项目的过程比较简单，注意在选择SDK 9的版本，使用Stage模型，如下：

业务逻辑梳理

1、权限问题，首先需要注册蓝牙相关权限；
2、搜索蓝牙，应用启动后可以手动的开启和关闭蓝牙扫描；
3、连接蓝牙，根据蓝牙的mac地址，调用connect进行连接；
4、遍历蓝牙特征，在蓝牙连接成功后，获取蓝牙的服务特征，设置指定GATT特征通知；
5、通知数据，将数据通过蓝牙服务中的通知属性发送；
6、接受通知，中心设备通过characteristicChangedEvent接收通知数据，并显示在屏幕上；
7、断开蓝牙，根据需要断开连接的蓝牙；
8、关闭蓝牙，在应用退出，需要结束扫描，释放资源。

开发实践

1、申请权限

开发之前，通过API文档可以指导，需要实现目标需要获得以下权限：

• ohos.permission.USE_BLUETOOTH // 允许应用查看蓝牙的配置。
• ohos.permission.DISCOVER_BLUETOOTH // 允许应用配置本地蓝牙，查找远端设备且与之配对连接。
• ohos.permission.LOCATION // 允许应用获取设备位置信息。
• ohos.permission.MANAGE_BLUETOOTH // 允许应用配对蓝牙设备，并对设备的电话簿或消息进行访问。

以上权限中ohos.permission.MANAGE_BLUETOOTH级别是system_basic，此权限在应用打包签名时需要在UnsgnedReleasedProfileTemplate.json文件中的acls字段下添加此权限，否则安装时会出现：Failed due to grant request permissions failed，具体原因可以查看：#夏日挑战赛#OpenHarmony 应用安装报权限错误，如下代码：

"acls": {
    "allowed-acls": [
      "ohos.permission.MANAGE_BLUETOOTH"
    ]
  }

如下图：

应用开发时，将需要申请的权限在modele.json5文件中声明，权限相关的说明可以查看：应用权限列表

"requestPermissions": [
      {
        "name": "ohos.permission.USE_BLUETOOTH",
        "reason": "$string:grant_use_bluetooth",
        "usedScene": {
          "abilities": [
            "MainAbility"
          ],
          "when": "inuse"
        }
      },
      {
        "name": "ohos.permission.DISCOVER_BLUETOOTH",
        "reason": "$string:grant_discovery_bluetooth",
        "usedScene": {
          "abilities": [
            "MainAbility"
          ],
          "when": "inuse"
        }
      },
      {
        "name": "ohos.permission.LOCATION",
        "reason": "$string:grant_location",
        "usedScene": {
          "abilities": [
            "MainAbility"
          ],
          "when": "inuse"
        }
      },
      {
        "name": "ohos.permission.MANAGE_BLUETOOTH",
        "reason": "$string:grant_manage_bluetooth",
        "usedScene": {
          "abilities": [
            "MainAbility"
          ],
          "when": "inuse"
        }
      }
    ]

2、打开并搜索蓝牙

2.1、打开蓝牙

• 打开蓝牙并监听蓝牙状态

let result:boolean = bluetooth.enableBluetooth() // 开启蓝牙

• 监听蓝牙状态（开启或关闭）

  /***
   * 添加监听器
   */
  addBlueListener() {
    // 订阅蓝牙连接状态改变事件。
    let self = this
    bluetooth.on('stateChange', (data) => {
      logger.info(TAG, `enter on stateChange`)
      // 蓝牙打开
      if (data === bluetooth.BluetoothState.STATE_ON) {
        logger.info(TAG, `enter BluetoothState.STATE_ON`)
        self.startBleScan()
      }
      // 蓝牙关闭
      if (data === bluetooth.BluetoothState.STATE_OFF) {
        logger.info(TAG, `enter BluetoothState.STATE_OFF`)
        self.disconnect()
        self.stopBleScan()
        bluetooth.stopBluetoothDiscovery() // 关闭蓝牙扫描
        self.mDeviceName = ''
        self.mDeviceRower = ''
        self.discoveryList = []
      }
      logger.info(TAG, `BluetoothState = ${JSON.stringify(data)}`)
    })
  }

2.2、bluetooth.getState()

点击蓝牙开关，进行开启和关闭蓝牙操作，程序启动后会先自动检测系统蓝牙是否开启，如果开启则打开蓝牙开关，默认状态下关闭蓝牙。蓝牙被开启后会进入蓝牙扫描。目前主要针对BLE低功耗蓝牙进行操作，所以这里只开启BLE蓝牙扫描，下面说到的蓝牙相关操作，都是指BLE蓝牙。

• 获取蓝牙状态

import bluetooth from '@ohos.bluetooth';

let state = bluetooth.getState()
    if (state === bluetooth.BluetoothState.STATE_ON) {
      this.isOn = true
      // 针对BLE蓝牙
      this.startBleScan() // 发现BLE蓝牙
    }
    if (state === bluetooth.BluetoothState.STATE_OFF) {
      this.isOn = false
    }

2.3、启动蓝牙扫描，并注册发现设备监听器

启动BLE蓝牙扫描，并注册“BLEDeviceFiind”蓝牙监听器，用于接收扫描到蓝牙，为了方便调试我这里只将需要的蓝牙设备过滤出来。扫描出来的蓝牙状态默认为：未连接

• bluetooth.BLE.startBLEScan()

• bluetooth.BLE.on(‘BLEDeviceFind’)

  /**
   * 开启BLE蓝牙扫描
   * @param data
   */
  startBleScan() {
    logger.info(TAG, `startBleScan`)
    bluetooth.BLE.on('BLEDeviceFind', this.onBLEDeviceFind)
    bluetooth.BLE.startBLEScan([{
                                  deviceId: DEVICE_MAC
                                }])
  }
  onBLEDeviceFind = (scanResult: Array<bluetooth.ScanResult>) => {
    let self = this
    //    logger.info(TAG, `BLE scan device find result= ${JSON.stringify(scanResult)}`)
    if (typeof (scanResult) === 'undefined' || scanResult.length <= 0) {
      return
    }
    for (let result of scanResult) {
      let temp: string = result.deviceId
      //  只过滤需要的设备
      if (DEVICE_MAC !== temp) {
        break
      }
      if (!self.isExistDevice(self.discoveryList, temp)) {
        self.createBleBlueInfo(temp, result.rssi).then((info) => {
          logger.info(TAG, `BLE scan device find，add = ${JSON.stringify(info)}`)
          // 连续两次发送相同的广播，时间间隔5ms，过滤极短时间发现的设备
          let curTime: number = Date.now()
          let diff: number = curTime - self.mLastFindDeviceTime
          logger.info(TAG, `BLE scan device find，Time diff = ${diff} curTime=${curTime}  mLastFindDeviceTime=${self.mLastFindDeviceTime}`)
          if (diff > 5) {
            logger.info(TAG, `BLE scan device find，Time is less than 5 ms, so back`)
            self.discoveryList.push(info)
          }
          this.mLastFindDeviceTime = curTime
        });
      } else {
        let curBlueInfo: baseInfo = self.getBlueInfoByDeviceId(self.discoveryList, temp)
        if (curBlueInfo !== null) {
          curBlueInfo.deviceRssi = result.rssi
          logger.info(TAG, `BLE scan device find，update rssi = ${curBlueInfo.deviceRssi}`)
          let index: number = self.getIndexByDeviceId(self.discoveryList, temp)
          if (index >= 0) {
            self.discoveryList.splice(index, 1)
            logger.info(TAG, `BLE scan device find，delete index= ${index}`)
            self.discoveryList.push(curBlueInfo)
            logger.info(TAG, `BLE scan device find，add new info = ${JSON.stringify(curBlueInfo)}`)
          }
        }
      }
    }
  }

抛出问题

问题1：在bluetooth.BLE.startBLEScan()接口中传递需要过滤的deviceId，但是无效，问题已向社区反馈，如果有兴趣可以关注相关 issues

3、连接蓝牙

点击列表中的蓝牙信息，根据当前的状态发起蓝牙连接，涉及的接口：GattClientDevice.connect()

返回值：

this.mGattClientDevice = bluetooth.BLE.createGattClientDevice(deviceId)
let connectStatus = this.mGattClientDevice.connect()
logger.info(TAG, `BLE Device connect = ${connectStatus}`)

4、获取蓝牙服务，遍历蓝牙特征

通过GattClientDevice.on(type: “BLEConnectionStateChange”, callback: Callback<BLEConnectChangedState>)注册蓝牙连接状态变化监听器，获取蓝牙连接状态，当蓝牙连接成功，则通过GattClientDevice.getServices() 获取蓝牙支持的服务，这里提醒一句，获取服务需要耗时3秒左右，通过蓝牙服务设置
readCharacteristicValue()、writeCharacteristicValue()、setNotifyCharacteristicChanged()、on(‘BLECharacteristicChange’) 来完成对蓝牙的读、写、监听特征值变化的操作。

• 通过GattClientDevice.getServices()

        // BLE蓝牙连接成功，获取当前BLE蓝牙的服务
        this.mGattClientDevice.getServices().then((result: Array<bluetooth.GattService>) => {
          logger.info(TAG, `BLE Device getServices successfully`)
          for (let blueService of result) {
            logger.info(TAG, `BLE Device blue ${connectDeviceId} Service uuid=${blueService.serviceUuid}`)
            if (SERVICE_UUID === blueService.serviceUuid) {
              let curCharacteristics = blueService.characteristics
              for (let characteristic of curCharacteristics) {
                logger.info(TAG, `BLE Device characteristic= ${JSON.stringify(characteristic)}`)
                if (NOTIFY_UUID === characteristic.characteristicUuid) {
                  self.mNotifyCharacteristic = characteristic
                  self.blueSetNotifyCharacteristicChanged()
                } else if (WRITE_UUID === characteristic.characteristicUuid) {
                  self.mWriteCharacteristic = characteristic
                  logger.info(TAG, `BLE Device blue send ： 获得WriteCharacteristic `)
                  // 延迟500ms再向蓝牙设备发送获取设备信息消息，防止未注册消息通知导致无法收到
                  setTimeout(() => {
                    self.getDeviceInfo()
                  }, 100)
                }
              }
            }
            // todo 使用ReadCharacteristic 时会导致WriteCharacteristic、NotifyCharacteristic失败，这里先注释
            //            else if (SERVICE_BATTERY_UUID === blueService.serviceUuid) {
            //              // 监听BLE设备主动发送的消息
            //              let curCharacteristics = blueService.characteristics
            //              for (let characteristic of curCharacteristics) {
            //                logger.info(TAG, `BLE Device characteristic2= ${JSON.stringify(characteristic)}`)
            //                if (LEVEL_BATTERY_UUID === characteristic.characteristicUuid) {
            //                  self.mReadCharacteristic = characteristic
            //                  self.blueSetReadCharacteristic()
            //                }
            //              }
            //            }
          }
        });
      } else if (connectState === bluetooth.ProfileConnectionState.STATE_DISCONNECTED) {
        // 断开连接
        this.refreshBleConnect(connectDeviceId, STATE.DISCONNECT)
        this.mDeviceName = ''
        this.mDeviceRower = ''
      } else if (connectState === bluetooth.ProfileConnectionState.STATE_CONNECTING) {
        // 连接中
        this.refreshBleConnect(connectDeviceId, STATE.CONNECTING)
        this.mDeviceName = ''
        this.mDeviceRower = ''
      }
    })

5、向低功耗蓝牙设备写入特定的特征值

通过步骤4可以获取到BLECharacteristic，调用：GattClientDevice.writeCharacteristicValue() 就可以向低功耗蓝牙设备写入特定的特征值。

  blueWriteCharacteristicValue(str: string) {
    if (this.mWriteCharacteristic === null) {
      return
    }
    let strUpper: string = str.toUpperCase()
    let temp: string = HexUtil.stringToHex(strUpper)
    let dataPacket: string = HexUtil.getWriteDataPacket(temp)
    let data: Uint8Array = HexUtil.hexStringToBytes2(dataPacket)
    this.mWriteCharacteristic.characteristicValue = data.buffer
    let success: boolean = this.mGattClientDevice.writeCharacteristicValue(this.mWriteCharacteristic)
    logger.info(TAG, `BLE Device WriteCharacteristicValue  success =${success}`)
  }

6、接受通知

向服务端发送设置通知此特征值请求：setNotifyCharacteristicChanged(characteristic: BLECharacteristic, enable: boolean)

  blueSetNotifyCharacteristicChanged() {
    logger.info(TAG, `BLE Device SetNotifyCharacteristicChanged`)
    let success1: boolean = this.mGattClientDevice.setNotifyCharacteristicChanged(this.mNotifyCharacteristic, true)
    logger.info(TAG, `BLE Device SetNotifyCharacteristicChanged success1=${success1}`)
    logger.info(TAG, `BLE Device blue send ：  注册通知监听器 success1 =${success1}`)
    if (success1) {
      this.onBLECharacteristicChange()
      let descriptor: bluetooth.BLEDescriptor = this.getDescriptor(this.mNotifyCharacteristic, this.mNotifyCharacteristic.characteristicUuid);
      if (descriptor != null) {
        descriptor.descriptorValue = new Uint8Array(this.ENABLE_NOTIFICATION_VALUE).buffer
        let success2: boolean = this.mGattClientDevice.writeDescriptorValue(descriptor)
        logger.info(TAG, `BLE Device SetNotifyCharacteristicChanged success2=${success2}`)
      } else {
        logger.info(TAG, `BLE Device SetNotifyCharacteristicChanged descriptor is null`)
      }
    }
  }

• 订阅蓝牙低功耗设备的特征值变化事件：GattClientDevice.on(type: “BLECharacteristicChange”, callback: Callback<BLECharacteristic>)

  /**
   *订阅蓝牙低功耗设备的特征值变化事件。
   * 需要先调用setNotifyCharacteristicChanged接口才能接收server端的通知。
   * @param deviceId
   */
  onBLECharacteristicChange() {
    this.mGattClientDevice.on('BLECharacteristicChange', (data: bluetooth.BLECharacteristic) => {
      let serviceUuid = data.serviceUuid;
      let characteristicUuid = data.characteristicUuid;
      logger.info(TAG, `BLE Device data on BLECharacteristicChange ${serviceUuid}, ${characteristicUuid}`)
      let characteristicValue:ArrayBuffer = data.characteristicValue
      if (characteristicValue !== null && typeof(characteristicValue) === 'undefined') {
        return
      }
      let valueTemp = HexUtil.ab2hex(characteristicValue);
      let value = HexUtil.filterValue(valueTemp)
      let temp: string = HexUtil.hexToString(value)
      let tempStrs: string[] = temp.split(',')
      let count: number = tempStrs.length
      let curStr: string = tempStrs[count - 1] + '\n'
      // 解析设备基础信息
      this.analysisDeviceInfo(curStr)
      // 解析设备电量信息
      this.analysisRower(curStr)
      if (this.filterResult(curStr)) {
        return
        }
      this.mScanStr = curStr + '' + this.mScanStr
    })
  }

抛出问题

问题1：监听多服务通道特征通知会导致异常，相关issues

7、断开蓝牙

蓝牙连接成功后，点击蓝牙列表中的蓝牙信息，弹窗窗口提示用户需要断开蓝牙，点击"确定"则断开蓝牙，涉及的接口：GattClientDevice.disconnect()

• 提示弹窗

AlertDialog.show({
          title: $r('app.string.disconnect'),
          message: '此操作将会断开您与以下设备的连接：' + ((typeof (blue.deviceName) !== 'undefined') ? blue.deviceName : blue.deviceId),
          primaryButton: {
            value: $r('app.string.cancel'),
            action: () => {
            }
          },
          secondaryButton: {
            value: $r('app.string.confirm'),
            action: () => {
              this.disconnectBlue(blue)
            }
          }
        })

• 断开蓝牙

  /**
   * 断开蓝牙
   * @param blue
   */
  disconnectBlue(blue: baseInfo) {
    logger.info(TAG, `disconnectBlue info = ${JSON.stringify(blue)}`)
    if (blue === null || typeof (this.mGattClientDevice) === 'undefined') {
      return
    }
    let deviceId: string = blue.deviceId
    let ret = this.mGattClientDevice.disconnect()
    logger.info(TAG, `BLE Device ${deviceId} disconnect Status = ${ret}`)
    if (ret === true) {
      this.removeBlueDevice(deviceId)
      this.mGattClientDevice = null
    } else {
      this.showToast('断开蓝牙失败')
    }
  }

8、关闭蓝牙

关闭蓝牙后，会通知再2.1中蓝牙关闭状态的回调

let result:boolean = bluetooth.disableBluetooth()

到此BLE低功耗蓝牙的整体流程就介绍完毕，如果有什么问题，可以在评论区留言。

问题与思考

1、BLE蓝牙创建加密通信通道时需要进行绑定，目前SDK9的版本上还不支持，只能使用不绑定的方式进行通信。相关 issues

补充代码

UI

 build() {
    Column() {
      Stack({ alignContent: Alignment.Top }) {
        Image($r('app.media.top_bg'))
          .objectFit(ImageFit.Cover)
        Row() {
          Text(this.mDeviceName)
            .width('30%')
            .fontColor('#71fbfd')
            .align(Alignment.Center)
            .textAlign(TextAlign.Center)
            .fontSize(32)
            .margin({
              bottom: '15%'
            })
          Image($r('app.media.project_hr22'))
            .objectFit(ImageFit.Contain)
            .width('30%')
            .onClick(() => {
              this.onClickDevice()
            })
          Text(`电量 ${this.mDeviceRower}%`)
            .width('30%')
            .margin({
              top: '20%'
            })
            .fontColor('#71fbfd')
            .align(Alignment.Center)
            .textAlign(TextAlign.Center)
            .fontSize(24)
        }
        .alignItems(VerticalAlign.Center)
        .justifyContent(FlexAlign.Center)
        .width('100%')
        .height('100%')
      }
      .width('100%')
      .height('40%')

      Divider()
        .vertical(false)
        .color('#fc3811')
        .strokeWidth(5)

      Column() {
        Row() {
          Column() {
            Text($r('app.string.bluetooth'))
              .fontSize(30)
              .alignSelf(ItemAlign.Start)
            if (true === this.isOn) {
              Row() {
                Text($r('app.string.discovery'))
                  .fontSize(20)
                  .alignSelf(ItemAlign.Start)
                  .margin({
                    top: '10'
                  })

                LoadingProgress()
                  .color(Color.Grey)
                  .width(30)
                  .height(30)
                  .align(Alignment.Center)
                  .margin({
                    left: 10
                  })
              }
              .height(40)
            }
          }.margin({ top: 20, bottom: 20 })

          Blank() // 空白填充

          Column() {
            Toggle({ type: ToggleType.Switch, isOn: this.isOn })
              .selectedColor('#ff2982ea')
              .key('toggleBtn')
              .onChange((isOn: boolean) => {
                if (isOn) {
                  this.isOn = true
                  let result:boolean = bluetooth.enableBluetooth() // 开启蓝牙
                  logger.info(TAG, `enable Bluetooth ${result}`)
                } else {
                  this.isOn = false
                  let result:boolean = bluetooth.disableBluetooth()
                  logger.info(TAG, `disable Bluetooth ${result}`)
                }
              })
          }
        }.width('100%')

        if (this.isOn) {
          Divider()
            .width('100%')
            .vertical(false)
            .color('#a3a4a7')
            .strokeWidth(1)
            .margin({
              bottom: '1%'
            })
        }


        Column() {
          ForEach(this.discoveryList, (item: baseInfo) => {
            Row() {
              Image(item.state === STATE.CONNECTED ? $r('app.media.blue_connect') :
                (item.state === STATE.CONNECTING ? $r('app.media.blue_connecting') : $r('app.media.blue_disconnect')))
                .width(45)
                .height(45)
                .objectFit(ImageFit.Cover)
                .margin({
                  right: '1%'
                })

              Column() {
                Text(item.deviceName)
                  .width('100%')
                  .fontSize(22)
                  .margin({
                    top: '2%',
                    bottom: '2%'
                  })
                Row() {
                  Text(item.deviceId)
                    .fontSize(16)
                  Text(item.deviceRssi.toString())
                    .fontSize(16)
                    .margin({
                      left: '5%'
                    })
                }
                .width('100%')
                .margin({
                  bottom: '2%'
                })
              }
            }
            .justifyContent(FlexAlign.Start)
            .alignSelf(ItemAlign.Start)
            .width('100%')
            .key('pairedDevice')
            .onClick(() => {
              this.onClickBlueItem(item)
            })
          })
        }
      }
      .width('90%')
      .padding({ top: 10, left: 30, right: 30, bottom: 10 })
      .margin({ top: 20, bottom: 20 })
      .backgroundColor(Color.White)
      .borderRadius(20)
      .borderWidth(1)
      .borderColor('#a3a4a7')

      Column() {
        Scroll(this.scroller) {
          Column() {
            Text(this.mScanStr)
              .width('100%')
              .fontSize(18)
              .lineHeight(30)
              .align(Alignment.Start)
          }
          .width('100%')
          .padding({
            left: '20',
            right: '20'
          })
          .alignSelf(ItemAlign.Start)
          .justifyContent(FlexAlign.Start)
        }
        .scrollable(ScrollDirection.Vertical)
        .scrollBarColor(Color.Gray)
        .scrollBar(BarState.Auto)
        .scrollBarWidth(10)
        .width('90%')
        .height('20%')
      }
      .padding({
        left: '20',
        right: '20',
        top: '20',
        bottom: '20'
      })
      .margin({
        bottom: '20'
      })
      .border({
        width: 1,
        color: '#a3a4a7'
      })
      .borderRadius(30)
      .backgroundColor(Color.White)


      Button('清除')
        .width('90%')
        .height(60)
        .backgroundColor('#fc3811')
        .fontSize(24)
        .onClick(() => {
          this.mScanStr = ''
        })
    }
    .width('100%')
    .height('100%')
    .backgroundColor('#dcdcdc')
  }

数据转换工具：HexUtil

import TextUtils from './TextUtils'

type char = string;
type byte = number;

export default class HexUtil {
  private static readonly DIGITS_LOWER: char[] = ['0', '1', '2', '3', '4', '5',
  '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'];
  private static readonly DIGITS_UPPER: char[] = ['0', '1', '2', '3', '4', '5',
  '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'];
  private static readonly UPDATE_HEAD: string = 'xxxxxxxx';
  private static readonly WRITE_PACKET_DATE_START: string = "xxxxxxxxx"; //发送数据固定起始数据域格式
  public static readonly WRITE_PACKET_DATE_END: string = "xxxx"; // 发送数据固定结束数据域格式
  public static readonly NOTIFY_DATE_START: string = "xxxxxxxx"; // 通知数据头
  public static readonly NOTIFY_DATE_END: string = "xxxxxxxxx"; // 通知数据尾

  public static encodeHex(data: byte[], toLowerCase: boolean = true): char[] {
    return HexUtil.encodeHexInner(data, toLowerCase ? HexUtil.DIGITS_LOWER : HexUtil.DIGITS_UPPER);
  }

  protected static encodeHexInner(data: byte[], toDigits: char[]): char[] {
    if (!data)
    return null;
    let l: number = data.length;
    let out: char[] = new Array(l << 1);
    let index:number = 0
    for(let item of data) {
      index += 1
      out[index] = toDigits[(0xF0 & item) >>> 4]
      index += 1
      out[index] = toDigits[0x0F & item]
    }
    return out;
  }

  protected static encodeHexInner2(data: Uint8Array, toDigits: char[]): char[] {
    if (!data)
    return null;
    let l: number = data.length;
    let out: char[] = new Array(l << 1);
    let index:number = 0
    for(let item of data) {
      index += 1
      out[index] = toDigits[(0xF0 & item) >>> 4]
      index += 1
      out[index] = toDigits[0x0F & item]
    }
    return out;
  }

  private static byteToString(data: char[]): string {
    let str = '';
    for(let item of data) {
      str += item
    }
    return str;
  }

  public static encodeHexStr(data: byte[], toLowerCase: boolean = true): string{
    return HexUtil.encodeHexStrInner(data, toLowerCase ? HexUtil.DIGITS_LOWER : HexUtil.DIGITS_UPPER);
  }

  protected static encodeHexStrInner(data: byte[], toDigits: char[]): string {
    return HexUtil.byteToString(HexUtil.encodeHexInner(data, toDigits));
  }

  public static encodeHexStr2(data: Uint8Array, toLowerCase: boolean = true): string{
    return HexUtil.encodeHexStrInner2(data, toLowerCase ? HexUtil.DIGITS_LOWER : HexUtil.DIGITS_UPPER);
  }

  protected static encodeHexStrInner2(data: Uint8Array, toDigits: char[]): string {
    return HexUtil.byteToString(HexUtil.encodeHexInner2(data, toDigits));
  }

  public static formatHexString(data: Uint8Array, addSpace: boolean = false): string {
    if (!data || data.length < 1)
    return null;
    let sb: string = '';
    for (let item of data) {
      let hex: String = (item & 0xFF).toString(16);
      if (hex.length == 1) {
        hex = '0' + hex;
      }
      sb = sb + hex;
      if (addSpace)
      sb = sb + " ";
    }
    return sb;
  }

  public static decodeHex(data: char[]): byte[] {
    let len: number = data.length;

    if ((len & 0x01) != 0) {
      throw new Error("Odd number of characters.");
    }

    let out: byte[] = new Array(len >> 1);
    let i:number = 0
    let j:number = 0
    while(j < len) {
      let f : number = HexUtil.toDigit(data[j], j) << 4
      j += 1
      f = f | HexUtil.toDigit(data[j], j)
      j += 1
      out[i] = (f & 0xFF)
    }
    return out;
  }

  protected static toDigit(ch: char, index: number): number {
    let digit: number = HexUtil.charToByte(ch.toUpperCase()); //Character.digit(ch, 16);
    if (digit == -1) {
      throw new Error("Illegal hexadecimal character " + ch
      + " at index " + index);
    }
    return digit;
  }

  public static hexStringToBytes(hexString: string): Uint8Array {
    if (TextUtils.isEmpty(hexString)) {
      return null;
    }
    hexString = hexString.trim();
    hexString = hexString.toUpperCase();
    let length: number = hexString.length / 2;
    let hexChars: char[] = TextUtils.toCharArray(hexString);
    let d: byte[] = new Array(length);
    let index = 0
    while (index < length) {
      let pos = index * 2;
      d[index] = (HexUtil.charToByte(hexChars[pos]) << 4 | HexUtil.charToByte(hexChars[pos + 1]));
      index += 1
    }
    return new Uint8Array(d);
  }

  public static hexStringToBytes2(hexString: string): Uint8Array {
    if (TextUtils.isEmpty(hexString)) {
      return null;
    }
    hexString = hexString.trim();
    hexString = hexString.toUpperCase();
    let length: number = hexString.length / 2;
    let hexChars: char[] = TextUtils.toCharArray(hexString);
    let d: byte[] = new Array(length);
    let index = 0
    while (index < length) {
      let pos = index * 2;
      d[index] = (HexUtil.charToByte(hexChars[pos]) << 4 | HexUtil.charToByte(hexChars[pos + 1]));
      index += 1
    }
    return new Uint8Array(d);
  }

  public static charToByte(c: char): byte {
    return "0123456789ABCDEF".indexOf(c);
  }

  public static extractData(data: Uint8Array, position: number): String {
    return HexUtil.formatHexString(new Uint8Array([data[position]]));
  }

  public static getWriteDataPacket(hexString: string): string {
    if (TextUtils.isEmpty(hexString) || hexString.length % 2 !== 0) {
      return ''
    }

    let dataField: string = ''
    if (hexString.startsWith(HexUtil.UPDATE_HEAD)) {
      dataField = hexString.replace(HexUtil.UPDATE_HEAD, '')
    } else {
      dataField = HexUtil.WRITE_PACKET_DATE_START.concat(hexString, HexUtil.WRITE_PACKET_DATE_END)
    }
    return dataField
  }

  public static stringToHex(s: string): string {
    let str: string = ''
    let len: number = s.length
    let index: number = 0
    while (index < len) {
      let ch: number = s.charCodeAt(index)
      let s4: string = ch.toString(16)
      str = str + s4
      index += 1
    }
    return str
  }

  public static hexToString(data:string):string {
    let val : string = ''
    let arr:string[] = data.split(',')
    let index:number = 0
    while(index < arr.length) {
      val += String.fromCharCode(parseInt(arr[index], 16))
      index += 1
    }
    let b:string = decodeURIComponent(val)
    console.log('hexToString b' + b)
    return b
  }

  public static  ab2hex(buffer:ArrayBuffer):string {
    var hexArr = Array.prototype.map.call(
      new Uint8Array(buffer),
      function (bit) {
        return ('00' + bit.toString(16)).slice(-2)
      }
    )
    return hexArr.join(',');
  }

  /**
   * 过滤通知消息头和消息尾
   * @param data
   */
  public static filterValue(data:string) : string {
    if (data === null) {
      return ''
    }
    return data.replace(this.NOTIFY_DATE_START, '').replace(this.NOTIFY_DATE_END, '')
  }
}

字符工具：TextUtils

export default class TextUtils{
    public static isEmpty(text: string): boolean {
        return text == null || text == undefined || text.length==0;
    }

    public static toCharArray(text: string): Array<string> {
        let arr: string[] = new Array(text.length);
        let index = 0
        while(index < text.length) {
            arr[index] = text.charAt(index);
            index += 1
        }
        return arr;
    }
}

感谢

如果您能看到最后，还希望您能动动手指点个赞，一个人能走多远关键在于与谁同行，我用跨越山海的一路相伴，希望得到您的点赞。