在BLE设备中值变化时如何更新BatteryLevel

Question

func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService, error: Error?) {

    for c in service.characteristics!{
        print("---Characteristic found with UUID: \(c.uuid) \n")

        let uuid = CBUUID(string: "2A19")//Battery Level

        if c.uuid == uuid{
            peripheral.setNotifyValue(true, for: c)//Battery Level
        }
    }
}
}
func peripheral(_ peripheral: CBPeripheral, didUpdateValueFor characteristic: CBCharacteristic, error: Error?) {
/* Battery Level */
if (characteristic.uuid == CBUUID(string: "2A19")) && (characteristic.value != nil){
    let value = characteristic.value
    let valueUint8 = [UInt8](value!)
    print("\(valueUint8)")
    print("\(valueUint8[0])")
    let batteryLevel: Int32 = Int32(bitPattern: UInt32(valueUint8[0]))
    print("\(batteryLevel)")

}
}

我想得到当前的电池水平，当它改变，但没有收到任何响应，即使我设置setNotifyValue。

Answer 1

我认为您需要在方法func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService, error: Error?)中读取值。

使用Objective，您可以在委托方法中这样做：

- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(nullable NSError *)error{
    for (CBCharacteristic *characteristic in service.characteristics) {

        [peripheral setNotifyValue:YES forCharacteristic:characteristic];

        // read battery
        if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:@"2A19"]]) {
            [peripheral readValueForCharacteristic:characteristic];//you miss the codes 
        }


    }

在另一种委托方法中：

- (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(nullable NSError *)error{
        if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:@"2A19"]]) {
        Byte *batteryBytes=(Byte*)characteristic.value.bytes;
        int battery = bytesToInt(batteryBytes, 0)&0xff;
        NSLog(@"%@", [NSString stringWithFormat:@"battery left:%d",battery]);
    }
}

我使用上述方法成功地获取了BLE设备的电池信息。