wx.notifyBLECharacteristicValueChange({               deviceId,               serviceId,               characteristicId: item.uuid,               state: true,               type: 'notification',               success(res) {                 console.log("参数"+deviceId+'---'+serviceId+'---'+item.uuid)                 console.log('notification通知数据', res)             },             fail(res) {                 console.log('notifyBLECharacteristicValueChange fali', res);             }             }) 执行完这个notify之后 参数都没问题 并且返回ok 但是无法进入wx.onBLECharacteristicValueChange()方法 就没办法拿到最新的特征值 这是什么问题呢