无论输入什么？监听到的都是一堆0，这是什么原因？

// 【6】获取服务

getServices() {

let that = this

uni.getBLEDeviceServices({

deviceId: that.deviceId,

success(res) {

that.serviceId = res.services[0].uuid

uni.showToast({

title: '获取服务成功'

})

},

fail(err) {

console.error(err)

uni.showToast({

title: '获取服务失败',

icon: 'error'

})

}

})

},

// 【7】获取特征值

getCharacteristics() {

let that = this

uni.getBLEDeviceCharacteristics({

deviceId: that.deviceId,

serviceId: that.serviceId,

success(res) {

that.characteristicId = res.characteristics[0].uuid //微信小程序调试

uni.showToast({

title: '获取特征值成功'

})

},

fail(err) {

console.error(err)

uni.showToast({

title: '获取特征值失败',

icon: 'error'

})

}

})

},

// 【8】开启消息监听

notify() {

let that = this

uni.notifyBLECharacteristicValueChange({

deviceId: that.deviceId, // 设备id

serviceId: that.serviceId, // 监听指定的服务

characteristicId: that.characteristicId, // 监听对应的特征值

state: true,

type:'notification',

success: (res) => {

console.log(res);

if (res.errMsg == "notifyBLECharacteristicValueChange:ok") {

console.log("开启消息监听------", res);

this.listenMessage()

}

},

fail(err) {

console.error(err)

uni.showToast({

title: '监听失败',

icon: 'error'

})

}

})

},

// 16进制字符串转ArrayBuffer

hex2ArrayBuffer() {

let hex_str = '68656c6c6f20776f726c64'

let typedArray = new Uint8Array(hex_str.match(/[\da-f]{2}/gi).map(function(h) {

return parseInt(h, 16)

}))

let buffer = typedArray.buffer

return buffer

},

// 【9】监听消息变化

listenMessage() {

let that = this

console.log(9999999)

uni.onBLECharacteristicValueChange((res) => {

console.log("发送过来的数据---------", res)

let resHex = that.ab2hex(res.value)

console.log(resHex)

that.messageHex = resHex

let result = that.hexCharCodeToStr(resHex)

console.log(String(result))

that.message = String(result)

})

},

// ArrayBuffer转16进度字符串示例

ab2hex(buffer) {

const hexArr = Array.prototype.map.call(

new Uint8Array(buffer),

function(bit) {

return ('00' + bit.toString(16)).slice(-2)

}

)

return hexArr.join('')

},

// 将16进制的内容转成我们看得懂的字符串内容

hexCharCodeToStr(hexCharCodeStr) {

var trimedStr = hexCharCodeStr.trim();

var rawStr = trimedStr.substr(0, 2).toLowerCase() === "0x" ? trimedStr.substr(2) : trimedStr;

var len = rawStr.length;

console.log(len)

if (len % 2 !== 0) {

alert("存在非法字符!");

return "";

}

var curCharCode;

var resultStr = [];

for (var i = 0; i < len; i = i + 2) {

curCharCode = parseInt(rawStr.substr(i, 2), 16);

resultStr.push(String.fromCharCode(curCharCode));

}

console.log(resultStr)

return resultStr.join("");

},