https://www.cnblogs.com/ckfuture/p/16450418.html

https://www.cnblogs.com/yangxiaobai123/p/16021058.html

字符串转base64：https://www.cnblogs.com/sunny3158/p/17312158.html 

将 ArrayBuffer 对象转成 Base64 字符串：基础 - uni.arrayBufferToBase64 - 《uni-app API 文档》 - 书栈网 · BookStack 

ArrayBuffer：https://zhuanlan.zhihu.com/p/655456833 

最近在做一个项目，要求app通过蓝牙连接设备并将报文传输至设备中，在这个过程踩过了几个坑，总结如下：

根据uni-app官网API主要涉及到“蓝牙”和“低功耗蓝牙”两个部分。

主要步骤：

步骤1：初始化蓝牙模块 openBluetoothAdapter

            $openBluetoothAdapter(){uni.openBluetoothAdapter({success: (res) => {//初始化成功，搜索设备console.log('openBluetoothAdapter success', res);uni.showLoading({title: '搜索设备中'});setTimeout(()=>{this.baseList=[];//每次扫码清空设备列表，不然会导致重复this.$startBluetoothDevicesDiscovery();//扫码蓝牙设备},100);//定时关闭搜索设备setTimeout(()=>{this.$stopBluetoothDevicesDiscovery();uni.hideLoading();},10*1000);},fail: (res) => {uni.showToast({title: '请打开蓝牙',duration: 1000});if (res.errCode === 10001) {//监听蓝牙适配器状态变化事件uni.onBluetoothAdapterStateChange(function(res){console.log('onBluetoothAdapterStateChange', res);if (res.available) {//开始扫描this.$startBluetoothDevicesDiscovery()}})}}})},

步骤2：搜索附近的蓝牙外围设备 startBluetoothDevicesDiscovery

            //2.搜索附近的蓝牙外围设备$startBluetoothDevicesDiscovery(){if (this._discoveryStarted) {return;}this._discoveryStarted = true;//开始搜寻附近的蓝牙外围设备uni.startBluetoothDevicesDiscovery({allowDuplicatesKey: true,success: (res) => {console.log('startBluetoothDevicesDiscovery success', res);//监听寻找到新设备的事件this.$onBluetoothDeviceFound()},fail:err=>{console.error("startBluetoothDevicesDiscoveryErr",err);uni.showToast({icon:'none',duration:2000,title:"请检查蓝牙状态",});}})},

步骤3：监听寻找到新设备 onBluetoothDeviceFound

            $onBluetoothDeviceFound(){let that =this;//监听寻找到新设备的事件uni.onBluetoothDeviceFound(function(res){res.devices.forEach(device => {if (!device.name && !device.localName) {return;}//添加蓝牙设备列表let oneBluetooth={deviceId: device.deviceId,name: device.name,RSSI:device.RSSI,localName:device.localName}            //判断是否存在if(that.bluetoothIndex.indexOf(device.deviceId) ==-1){that.baseList.push(oneBluetooth);that.bluetoothIndex.push(device.deviceId);}//如果名字相同连接设备//if(device.name == devicename){//$createBLEConnection(device.deviceId);//}})})},

步骤4：创建连接蓝牙事件  createBLEConnection

            $createBLEConnection(deviceId){let that=this;//1）判断设备是否处于连接状态if(that.Connecting){uni.showToast({icon:'none',duration:2000,title:"设备已连接",});return} //2）创建连接uni.showLoading({title: '设备连接中',mask:true,});uni.createBLEConnection({deviceId:deviceId,success: (res) => {that._deviceId = deviceId;//不延迟造成获取不到服务！！！！，我走过的坑！！！setTimeout(function() {//获取设备的蓝牙服务that.$getBLEDeviceServices(deviceId);//关闭等待提示setTimeout(function () {uni.hideLoading();}, 100);}, 7000);},fail: (err) =>{console.log(err);}});//3）设置MTU，否则传输报文不全，默认是23bytes，但是蓝牙本身是需要3bytes，故而只能传输20bytessetTimeout(()=>{console.log('deviceId>>>',deviceId);uni.setBLEMTU({deviceId:deviceId,mtu:255,success:(res)=>{console.log('设置MTU最大值成功',res);},fail:(res)=>{console.log('设置MTU最大值失败',res);}});},9000);//4）关闭搜索this.$stopBluetoothDevicesDiscovery();},

步骤5：获取蓝牙设备的所有服务 getBLEDeviceServices

            $getBLEDeviceServices(deviceId){//获取蓝牙设备所有服务(service)uni.getBLEDeviceServices({deviceId,success: (res) => {console.log('250res.services>>>',res.services);for (let i = 0; i < res.services.length; i++) {if (res.services[i].isPrimary) {this.$getBLEDeviceCharacteristics(deviceId, res.services[i].uuid);return;}}}});},

步骤6：获取蓝牙设备某个服务中所有特征值（characteristic）getBLEDeviceCharacteristics

            $getBLEDeviceCharacteristics(deviceId,serviceId){let that = this;//获取蓝牙设备某个服务中所有特征值(characteristic)。uni.getBLEDeviceCharacteristics({deviceId,serviceId,success: (res) => {console.log('288getBLEDeviceCharacteristics success', res.characteristics);for (let i = 0; i < res.characteristics.length; i++) {let item = res.characteristics[i]//if (item.properties.read) {//读取低功耗蓝牙设备的特征值的二进制数据值。1uni.readBLECharacteristicValue({deviceId,serviceId,characteristicId: item.uuid,})//}if (item.properties.write) {this._deviceId = deviceId;this._serviceId = serviceId;this._characteristicId = item.uuid;//写入请求数据this.$writeBLECharacteristicValue();                                }//if (item.properties.notify || item.properties.indicate) {//启用低功耗蓝牙设备特征值变化时的 notify 功能，订阅特征值。uni.notifyBLECharacteristicValueChange({deviceId,serviceId,characteristicId: item.uuid,state: true,success(res) {// console.log('notifyBLECharacteristicValueChange success:' + res.errMsg);// console.log(JSON.stringify(res));uni.onBLECharacteristicValueChange(characteristic => {console.log('监听低功耗蓝牙设备的特征值变化事件成功>>');//将字节转换成16进制字符串var data = ab2hex(characteristic.value)//将16进制转成字符串let newdataStr = Buffer.from(data,'hex');//先把数据存在buf里面//that.btvalue=newdataStr.toString("utf-8");//使用toString函数就能转换成字符串//设备返回SNthat.SN=newdataStr.toString("utf-8");console.log('设备返回SN>>>',that.SN);//根据返回的数据处理设备类型和显示的输入区域-----------------that.getEquType(that.SN);});}});//}}},fail(res) {console.error('getBLEDeviceCharacteristics', res)}})},

步骤7：向蓝牙设备发送一个16进制数据

            $writeBLECharacteristicValue(){let buffer = new ArrayBuffer(1)let dataView = new DataView(buffer);dataView.setUint8(0, 0);//0x61 | 0uni.writeBLECharacteristicValue({deviceId: this._deviceId,serviceId: this._serviceId,//"0000FE61-0000-1000-8000-00805F9B34FB",characteristicId: this._characteristicId,value: buffer,success: function(res){console.log('350',res);},fail: function(res){console.log(res);}})},

步骤8：向蓝牙设备发送字符串数据 writeBLECharacteristicValueString

            $writeBLECharacteristicValueString(str){// 发送方式一let buffer = new ArrayBuffer(str.length);let dataView = new DataView(buffer);for (let i in str) {dataView.setUint8(i, str[i].charCodeAt() | 0);    //打印二进制字节//console.log('dataView.getUint8(i)>>',dataView.getUint8(i));}//延迟发送指令setTimeout(()=>{uni.writeBLECharacteristicValue({deviceId: this._deviceId,serviceId: this._serviceId,characteristicId: this._characteristicId,//"0000FE61-0000-1000-8000-00805F9B34FB",//,value: buffer,success: function(res){console.log("命令写入成功",res); },fail: function(res){console.error("命令写入失败",res);}});},2000);},

步骤9：关闭搜索  stopBluetoothDevicesDiscovery

            $stopBluetoothDevicesDiscovery(){//关闭搜索uni.stopBluetoothDevicesDiscovery({success(res) {this._discoveryStarted=false;}})},

步骤10：断开蓝牙设备连接 closeBLEConnect

            $closeBLEConnect(deviceId){uni.closeBLEConnection({deviceId,success:res=>{this.deviceId = "";console.log("断开成功",res);},fail:err=>{console.error("断开错误",err);}})},

需要注意的是：

1）和蓝牙设备通讯不能太频繁。

2）写入数据时候要注意特性值UUID。

3）写入数据超过20bytes时候需要设置MTU。否则传输的内容将被截取，造成传输信息不完整。