关于蓝牙接收调试时value值为空的问题

小灰灰 2021-07-26 15:04 925阅读 0赞

**框架：** uni app

**原因：因为接收的是二进制流数据**

uint8arr = new Uint8Array(buffer); //二进制转无符号整数
    console.log(uint8arr ); //打印接收数据即可

在下面代码中通过ab2hex(buffer)函数转换成16进制字符串。

/** * 开启订阅特征值 */
    			notifyBLECharacteristicValue() { 
    				let deviceId = this.deviceId;
    				let serviceId = this.serviceId;
    				// let characteristicId = this.characteristicId[0].notifyId;
    				 let characteristicId = this.characteristicsLists[0].uuid;
    				 console.log('notifyBLECharacteristicValue - characteristicId : ', characteristicId);
    				// console.log('notifyBLECharacteristicValue - this.characteristicId : ', JSON.stringify(this.characteristicId));
    				let notify = true;
    				let self = this;
    				uni.notifyBLECharacteristicValueChange({ 
    					state: true, // 启用 notify 功能
    					// 这里的 deviceId 需要已经通过 createBLEConnection 与对应设备建立链接 
    					deviceId,
    					// 这里的 serviceId 需要在 getBLEDeviceServices 接口中获取
    					serviceId,
    					// 这里的 characteristicId 需要在 getBLEDeviceCharacteristics 接口中获取
    					characteristicId,
    					success(res) { 
    						console.log('uni.notifyBLECharacteristicValueChange - res : ', JSON.stringify(res));
    						// uni.hideLoading();
    						uni.showToast({ 
    							title: '连接成功',
    							icon: 'success'
    						});
    						// ArrayBuffer转16进度字符串示例
    						function ab2hex(buffer) { 
    							const hexArr = Array.prototype.map.call(
    								new Uint8Array(buffer),
    								function(bit) { 
    									return ('00' + bit.toString(16)).slice(-2)
    								}
    							)
    							return hexArr.join('')
    						}
    						uni.onBLECharacteristicValueChange(function(res) { 
    							console.log('uni.onBLECharacteristicValueChange');
    							console.log("特征值改变："+JSON.stringify(res));
    							console.log(`characteristic ${ res.characteristicId} has changed, now is ${ JSON.stringify(res.value)}`)
    							var value = ab2hex(res.value);
    							 console.log("ArrayBuffer转16进度字符串完成："+value)
    
    						});
    					},
    					fail(res) { 
    						console.log('notifyBLECharacteristicValueChange failed:' + res.errMsg);
    					}
    				});
    			},