起因是写了一个升级程序，通过蓝牙向设备写入，在安卓端一切正常，但在ios系统，就有一些问题。

现像：ios端，第一次连接上蓝牙以后，可以正常升级写入，第二次以及之后的连接，就不调用writeBLECharacteristicValue()函数写入了，过一会之后，会自动断开蓝牙连接，如下图：

代码：

// 1.打开蓝牙适配器
			openBle() {
				var that = this;
				uni.openBluetoothAdapter({
					success() {
						console.log('打开蓝牙适配器成功！');
						that.discoveryBle();
					},
					fail(err) {
						console.error('打开蓝牙适配器失败', err);
						uni.showToast({
							title: '请打开蓝牙！',
							icon: 'none'
						});
					}
				});
			},


			// 2.搜索蓝牙设备
			discoveryBle() {
				var that = this;
				uni.startBluetoothDevicesDiscovery({
					allowDuplicatesKey: false,
					success() {
						console.log('开始扫描蓝牙设备');
						that.listenBle();
					},
					fail(err) {
						console.error('扫描蓝牙设备失败', err);
					}
				});
			},


			// 3.监听扫描到的蓝牙设备
			listenBle() {
				var that = this;
				uni.onBluetoothDeviceFound((res) => {
					var devices = res.devices;
					for (var i in devices) {
						// console.log("蓝牙设备：",devices);
						if (that.isMyDevice(devices[i])) {
							uni.showToast({
								title: "找到" + that.ourDevice.length + "个设备",
								icon: 'none'
							});
						}
					}
					// 发送可连接的蓝牙列表给服务器
					if (that.isOurDevice) {
						that.isOurDevice = false;
						var data = JSON.stringify(that.ourDevice);
						var obj = {
							DataType: "BLE",
							Key: "Msg",
							Data: data,
							Msg: "显示信息"
						};
						var jsonString = JSON.stringify(obj);
						uni.sendSocketMessage({
							data: jsonString, // 发送 JSON 字符串
							success(res) {
								// console.log("发送蓝牙信息列表 " + jsonString + " 成功！");
							},
							fail(err) {
								console.error("发送数据失败", err);
							}
						});
					}
				});
			},


			// 4. 连接蓝牙设备
			connectToDevice(deviceId) {
				var that = this;
				if (targetDeviceID != deviceId) {
					targetDeviceID = deviceId;
					uni.createBLEConnection({
						deviceId: targetDeviceID,
						success(res) {
							that.isConnected = true;
							console.log(`设备 ${targetDeviceID} 连接成功`, res);
							uni.stopBluetoothDevicesDiscovery({
								success(res) {
									if (plateForm == 'ios') {
										console.log("当前平台是IOS");
										that.getService(); // 跳过设置MTU，直接获取服务UUID
									} else {
										console.log("当前平台是安卓");
										that.setMTU(); // 设置最大传输单元
									}
								}
							});
							uni.showToast({
								title: '蓝牙连接成功！',
								icon: 'success'
							});
						},
						fail(err) {
							console.error("连接错误信息：", err);
							if (err.errCode == -1) {
								// uni.showToast({
								// 	title: '已连接，请勿重复连接',
								// 	icon: 'none'
								// });
							} else if (err.errCode == 10003) {
								uni.showToast({
									title: '无法连接，请检查设备',
									icon: 'none'
								});
							} else {
								uni.showToast({
									title: '连接设备失败',
									icon: 'none'
								});
							}
						}
					});
				}
			},


			// 获取服务的UUID
			getService() {
				var that = this;
				uni.getBLEDeviceServices({
					deviceId: targetDeviceID,
					success(res) {
						console.log("获取服务UUID成功：", res);
						if (plateForm == 'ios') { // 设置IOS端的服务UUID
							if (res.services.length == 1) {
								serviceUUID = res.services[0].uuid; // 设置ESP32蓝牙服务的UUID
							} else {
								serviceUUID = res.services[1].uuid; // 设置蓝牙芯片服务的UUID
							}
						} else { // 设置Android端的服务UUID
							if (res.services.length == 3) {
								serviceUUID = res.services[0].uuid; // 设置ESP32蓝牙服务的UUID
							} else {
								serviceUUID = res.services[1].uuid; // 设置蓝牙芯片服务的UUID
							}
						}
						that.getCharacteris();
					},
					fail(err) {
						console.error("获取服务UUID失败：", err);
					}
				});
			},


			// 获取特征值的UUID
			getCharacteris() {
				var that = this;
				uni.getBLEDeviceCharacteristics({
					deviceId: targetDeviceID,
					serviceId: serviceUUID,
					success(res) {
						console.log("获取特征值UUID成功：", res);
						if (res.characteristics.length == 1) { // 设置ESP32蓝牙特征值的UUID
							characteristicIdUUID = res.characteristics[0].uuid;
							writeUUID = res.characteristics[0].uuid;
						} else { // 设置蓝牙芯片特征值的UUID
							characteristicIdUUID = res.characteristics[0].uuid;
							writeUUID = res.characteristics[1].uuid;
						}
						that.checkNotify();
					},
					fail(err) {
						console.error("读取特征值UUID失败：", err);
					}
				})
			},


			// 5.设置最大传输单元
			setMTU() {
				var that = this;
				uni.setBLEMTU({
					deviceId: targetDeviceID,
					mtu: 200,
					success() {
						uni.showToast({
							title: '参数设置成功！',
							icon: 'success'
						});
						that.getService(); // 获取服务UUID
					},
					fail(err) {
						console.error("设置最大传输单元失败：", err);
					}
				})
			},


			// 6.检查订阅
			checkNotify() {
				var that = this;
				// 6 . 订阅特征值
				console.log("服务：" + serviceUUID + "特征值：" + characteristicIdUUID);
				uni.notifyBLECharacteristicValueChange({
					deviceId: targetDeviceID,
					serviceId: serviceUUID,
					characteristicId: characteristicIdUUID,
					state: true,
					success() {
						uni.showToast({
							title: '设备连接正常!',
							icon: 'success'
						});
						setTimeout(function() {
							that.getValueChange();
						}, 1500);
					},
					fail(err) {
						console.error("无法读取设备数据：", err)
						uni.showToast({
							title: '无法读取设备数据',
							icon: 'fail'
						});
					}
				});


			},


			// 7. 监听低功耗蓝牙设备的特征值变化事件
			getValueChange() {
				var that = this;
				uni.onBLECharacteristicValueChange((res) => {
					var value = this.ab2hex(res.value);
					if (characteristicIdUUID == res.characteristicId) {
						this.sendDataToServer(value);
					}
					console.log("特征值变化:", value);
				});
			},


			// 8.断开连接
			disconnectDevice() {
				uni.closeBLEConnection({
					deviceId: targetDeviceID,
					success() {
						console.log('设备 ' + targetDeviceID + ' 断开连接');
						this.isConnected = false;
					},
					fail(err) {
						console.error('断开连接失败', err);
					}
				});
			},


			// 9.向蓝牙设备写入数据
			sendDataToBle(data) {
				// try {
				var that = this;
				const buffer = this.hex2buffer(data);
				uni.writeBLECharacteristicValue({
					deviceId: targetDeviceID,
					serviceId: serviceUUID,
					characteristicId: writeUUID,
					value: buffer,
					writeType: "write",
					success() {
						console.log(data + "已写入蓝牙设备！")
					},
					fail(err) {
						console.error('写入数据失败' + that.targetDeviceID, err);
						uni.showToast({
							title: '写入参数失败！',
							icon: 'none'
						});
					}
				});
				// } catch (error) {
				// 	console.error('蓝牙发送数据过程中发生错误：', error);
				// }
			},


			// 10.关闭蓝牙适配器
			closeBle() {
				uni.closeBluetoothAdapter({
					success(res) {
						console.log(res)
					}
				})
			}
		},
		onUnload() {
			var that = this;
			uni.stopBluetoothDevicesDiscovery({
				success(res) {
					console.log("停止搜索蓝牙");
				}
			});
			this.disconnectDevice();
			this.closeBle(); // 关闭蓝牙
			uni.closeSocket({
				success(res) {
					console.log("关闭Wbsocket连接成功！", res);
				}
			});


			this.cleanData(); //清除缓存数据
		},