wx.getBLEDeviceCharacteristics({             deviceId,             serviceId,             success: (res) => {                 console.log('getBLEDeviceCharacteristics success', res.characteristics)                 for (let i = 0; i < res.characteristics.length; i++) {                     let item = res.characteristics[i];                     let _uuid = item.uuid;                     let bindDevice = tthis.data.bindDevice;                     // 读取低功耗蓝牙设备的特征值的二进制数据值 注意：必须设备的特征值支持 read 才可以成功调用。                     if (item.properties.read) {                         bindDevice.read = true;                     }                     //向低功耗蓝牙设备特征值中写入二进制数据。注意：必须设备的特征值支持 write 才可以成功调用。                     if (item.properties.write) {                         bindDevice.serviceId = serviceId;                         bindDevice.characteristicId = _uuid;                         bindDevice.write = true;                         // callback ? callback() : ''                     }                     //启用低功耗蓝牙设备特征值变化时的 notify 功能，使用characteristicValueChange事件                     var uuid = ""                     if (item.properties.notify || item.properties.indicate) {                                                uuid=_uuid;                     }                                          wx.notifyBLECharacteristicValueChange({                         state: true, // 启用 notify 功能                         deviceId: deviceId,                         serviceId: serviceId,                         characteristicId: uuid,                         success(res) {                              console.log('第七步，启用notify成功', res.errMsg)                              let arrPrint = [];                             //初始化打印机                             arrPrint.push(util.sendDirective([0x1B, 0x40])); //16进制                             //居中对齐                             arrPrint.push(util.sendDirective([0x1B, 0x61, 0x01])); //居中                             //正文                             arrPrint.push(util.sendDirective([0x1B, 0x0E]));                             arrPrint.push(util.hexStringToBuff("\n葵花生活\n\n"));                             for(var jj=0;jj<arrPrint.length;jj++)                             for(var k=0;k<1;k++){  //连续打2次                                 var sendData ="你好，这是测试数据";                                 let buffer = arrPrint[jj];                                 var length = buffer.byteLength;                                 console.log("length:",length);                                 var count = Math.ceil(length/20); //最多执行 count 次                                 for(var i=0;i<count;i++){                                     //对buffer进行分包，最大不超过20字节                                     let TempBuffer="";                                     if(((i+1)*20)<length){                                         TempBuffer = buffer.slice(i*20,(i+1)*20);                                         console.log("正在进行第"+i+"次数据写入："+TempBuffer);                                         //写入设备                                         wx.writeBLECharacteristicValue({                                             deviceId: deviceId, //设备deviceId                                             serviceId: serviceId, //设备service_id                                             characteristicId:_characteristicId, //设备write特征值                                             value: TempBuffer, //写入数据                                             success: function (res) {                                                 console.log('writeBLECharacteristicValue success ->'+i, res)                                              },                                             fail: function (res) {                                                 console.log('writeBLECharacteristicValue fail', res)                                             }                                         })                                     }else{                                         TempBuffer = buffer.slice(i*20,length);                                         console.log("正在进行第"+i+"次数据写入："+TempBuffer);                                         //写入设备                                         wx.writeBLECharacteristicValue({                                             deviceId: deviceId, //设备deviceId                                             serviceId: serviceId, //设备service_id                                             characteristicId:_characteristicId, //设备write特征值                                             value: TempBuffer, //写入数据                                             success: function (res) {                                                 console.log('writeBLECharacteristicValue success ->'+i, res)                                              },                                             fail: function (res) {                                                 console.log('writeBLECharacteristicValue fail', res)                                             }                                         })                                     }                                     // tthis.sleep(i*0.02);  //延迟 i*200ms                                   }                                                               }                         },                         fail(e){                             console.log("fail:", JSON.stringify(e))                         }                     })                     //设置当前选中的蓝牙设备，包括是否可读写属性采集                     tthis.setData({                         bindDevice: bindDevice                     });                     console.log(tthis.data);                 }             },             fail(res) {                 console.error('获取特征值失败：', res)             }         })