android - 如何通过 scanRecord 识别 Eddystone

Question

我正在开发一款扫描 BLE 设备的 Android 应用程序。每次找到设备时，我都会收到: byte[] scanRecord, BluetoothDevice 设备, int rssi 来自 BluetoothAdapter.startLeScan()

然后我将字节数组转换为 ScanRecord 对象: ScanRecord.parseFromBytes()

我现在从我的 Eddystone 中获得了以下信息(来自 toString() 方法)。

`com.reelyactive.blesdk.support.ble.ScanRecord [mAdvertiseFlags=6, mServiceUuids=[0000feaa-0000-1000-8000-00805f9b34fb], mManufacturerSpecificData={}, mServiceData={0000feaa-0000-1000-8000-00805f9b34fb=[16, -36, 2, 107, 110, 116, 107, 46, 105, 111, 47, 101, 100, 100, 121, 115, 116, 111, 110, 101], 0000d00d-0000-1000-8000-00805f9b34fb=[67, 77, 103, 52, 50, 57, 100]}, mTxPowerLevel=-12, mDeviceName=IIS_EDDY_003] IIS_EDDY_003` 

谁能告诉我，如何使用这些信息将设备识别为 Eddystone？服务uuid​​可能吗？我并不总是知道设备的名称或地址。

Answer 1

android.bluetooth.le.ScanRecord 是 Android 中最糟糕的 API 之一。

如果你已经有了scanRecord(字节数组)，我推荐 nv-bluetooth 提取 Eddystone 数据。以下代码 fragment 显示了 nv-bluetooth 的用法。

// Parse the payload of the advertising packet.
List<ADStructure> structures =
    ADPayloadParser.getInstance().parse(scanRecord);

// For each AD structure contained in the payload.
for (ADStructure structure : structures)
{
    if (structure instanceof EddystoneUID)
    {
        // Eddystone UID
        EddystoneUID es = (EddystoneUID)structure;

        // (1) Calibrated Tx power at 0 m.
        int power = es.getTxPower();

        // (2) 10-byte Namespace ID
        byte[] namespaceId = es.getNamespaceId();
        String namespaceIdAsString = es.getNamespaceIdAsString();

        // (3) 6-byte Instance ID
        byte[] instanceId = es.getInstanceId();
        String instanceIdAsString = es.getInstanceIdAsString();

        // (4) 16-byte Beacon ID
        byte[] beaconId = es.getBeaconId();
        String beaconIdAsString = es.getBeaconIdAsString();
    }
    else if (structure instanceof EddystoneURL)
    {
        // Eddystone URL
        EddystoneURL es = (EddystoneURL)structure;

        // (1) Calibrated Tx power at 0 m.
        int power = es.getTxPower();

        // (2) URL
        URL url = es.getURL();
    }
    else if (structure instanceof EddystoneTLM)
    {
        // Eddystone TLM
        EddystoneTLM es = (EddystoneTLM)structure;

        // (1) TLM Version
        int version = es.getTLMVersion();

        // (2) Battery Voltage
        int voltage = es.getBatteryVoltage();

        // (3) Beacon Temperature
        float temperature = es.getBeaconTemperature();

        // (4) Advertisement count since power-on or reboot.
        long count = es.getAdvertisementCount();

        // (5) Elapsed time in milliseconds since power-on or reboot.
        long elapsed = es.getElapsedTime();
    }
    else if (structure instanceof IBeacon)
    {
        // iBeacon
        IBeacon iBeacon = (IBeacon)structure;

        // (1) Proximity UUID
        UUID uuid = iBeacon.getUUID();

        // (2) Major number
        int major = iBeacon.getMajor();

        // (3) Minor number
        int minor = iBeacon.getMinor();

        // (4) Tx Power
        int power = iBeacon.getPower();
    }
}

上面的代码暗示扫描记录应该被解析为AD结构的列表。但是，android.bluetooth.le.ScanRecord 的 parseFromBytes 没有以正确的方式解析扫描记录。

ScanRecord 具有以下方法(以及其他一些方法):

1. getAdvertiseFlags()
2. getDeviceName()
3. getManufacturerSpecificData()
4. getServiceData()
5. getTxPowerLevel()

这些方法对应一些AD结构。此 API 设计与下面所示的 AnimalRecord 类结构相同。

public class AnimalRecord
{
    public Cat getCat() { ... }
    public Dog getDog() { ... }
    public Eagle getEagle() { ... }
    ...
}

标志、本地名称、制造商特定数据、服务数据和 Tx 功率级别也应解析为如下所示的 AD 结构。

// Parse the payload of the advertising packet.
List<ADStructure> structures =
    ADPayloadParser.getInstance().parse(scanRecord);

// For each AD structure contained in the payload.
for (ADStructure structure : structures)
{
    if (structure instanceof Flags)
    {
        // Flags
        Flags flags = (Flags)structure;
    }
    else if (structure instanceof LocalName)
    {
        // Local Name
        LocalName name = (LocalName)structure;
    }
    else if (structure instanceof ADManufacturerSpecific)
    {
        // Manufacturer Specific Data
        // Note that iBeacon is a kind of Manufacturer Specific Data
        ADManufacturerSpecific ms = (ADManufacturerSpecific)structure;
    }
    else if (structure instanceof ServiceData)
    {
        // Service Data
        // Note that Eddystone is a kind of Service Data.
        ServiceData sd = (ServiceData)structure;
    }
    else if (structure instanceof TxPowerLevel)
    {
        // TxPowerLevel
        TxPowerLevel level = (TxPowerLevel)structure;
    }
}

正如上面代码中所注释的，Eddystone 是一种服务数据。因此，Eddystone UID、Eddystone URL 和 Eddystone TLM 应该具有如下继承树。

ADStructure
  |
  +-- ServiceData
        |
        +-- Eddystone
              |
              +-- EddystoneUID
              +-- EddystoneURL
              +-- EddystoneTLM

我希望那些非常了解BLE规范并具有良好设计能力的人能够从头开始重写Android的BLE API。