android解析蓝牙广播所携带的信息

前言

在可穿戴行业工作了两年，各种需求都碰到过，前段时间客户提出了一个要求蓝牙在广播的时候要携带一个特定的服务（UUID）,只有携带了此服务（UUID）的蓝牙设备才能被搜索到。之前都是以设备名称进行过滤的，突然改了一种方式当然要进行新的技术了解啊。

解决历程

因为是抓取蓝牙在广播的时候携带的信息，所以判断信息应该是在设备蓝牙被扫描到时可以抓取到信息，于是我们看扫描蓝牙的回调

private BluetoothAdapter.LeScanCallback mLeScanCallback = new BluetoothAdapter.LeScanCallback() {
public void onLeScan(BluetoothDevice device, int rssi, byte[] scanRecord) {
}
};

这是android扫描到蓝牙的回调，其中包括三个参数:

BluetoothDevice device：是蓝牙的一些基本信息（名称，mac地址等）。

int rssi：是蓝牙当前的信号值，绝对值越小信号越好。

byte[] scanRecord：字面理解是蓝牙的字节记录。

此时，蓝牙在广播时所携带的服务（UUID）最有可能在scanRecord里面，有了初步的估计就开始着手解析这个scanRecord，可是解析也需要知道规则才好解析啊，但是我对蓝牙的广播格式并不太了解，只能从android的代码层面想办法了，这时我发现android提供了一个ScanRecord的类，这一发现使我太开心了，然后我就取查看这个类发现这个类里面提供了一个方法

public static ScanRecord parseFromBytes(byte[] scanRecord){
}

得到解析广播后的ScanRecord实例。然后就可以直接调用里面的方法获取需要的信息了。希望总是美好的。

在实际的代码中发现不能ScanRecord.parseFromBytes(scanRecord)的方法得到实例，这个发现顿时把我给整蒙了，获取不到实例后面的也不能做啊。

但是问题还是要解决的，既然它提供了类那我也建一个类移植它的主要代码，代码如下

public class ScanRecordUtil{
private static final String TAG = "ScanRecordUtil";

// The following data type values are assigned by Bluetooth SIG.
// For more details refer to Bluetooth 4.1 specification, Volume 3, Part C, Section 18.
private static final int DATA_TYPE_FLAGS = 0x01;
private static final int DATA_TYPE_SERVICE_UUIDS_16_BIT_PARTIAL = 0x02;
private static final int DATA_TYPE_SERVICE_UUIDS_16_BIT_COMPLETE = 0x03;
private static final int DATA_TYPE_SERVICE_UUIDS_32_BIT_PARTIAL = 0x04;
private static final int DATA_TYPE_SERVICE_UUIDS_32_BIT_COMPLETE = 0x05;
private static final int DATA_TYPE_SERVICE_UUIDS_128_BIT_PARTIAL = 0x06;
private static final int DATA_TYPE_SERVICE_UUIDS_128_BIT_COMPLETE = 0x07;
private static final int DATA_TYPE_LOCAL_NAME_SHORT = 0x08;
private static final int DATA_TYPE_LOCAL_NAME_COMPLETE = 0x09;
private static final int DATA_TYPE_TX_POWER_LEVEL = 0x0A;
private static final int DATA_TYPE_SERVICE_DATA = 0x16;
private static final int DATA_TYPE_MANUFACTURER_SPECIFIC_DATA = 0xFF;

// Flags of the advertising data.
private final int mAdvertiseFlags;

@Nullable
private final List<ParcelUuid> mServiceUuids;

private final SparseArray<byte[]> mManufacturerSpecificData;

private final Map<ParcelUuid, byte[]> mServiceData;

// Transmission power level(in dB).
private final int mTxPowerLevel;

// Local name of the Bluetooth LE device.
private final String mDeviceName;

// Raw bytes of scan record.
private final byte[] mBytes;

/**
* Returns the advertising flags indicating the discoverable mode and capability of the device.
* Returns -1 if the flag field is not set.
*/
public int getAdvertiseFlags() {
return mAdvertiseFlags;
}

/**
* Returns a list of service UUIDs within the advertisement that are used to identify the
* bluetooth GATT services.
*/
public List<ParcelUuid> getServiceUuids() {
return mServiceUuids;
}

/**
* Returns a sparse array of manufacturer identifier and its corresponding manufacturer specific
* data.
*/
public SparseArray<byte[]> getManufacturerSpecificData() {
return mManufacturerSpecificData;
}

/**
* Returns the manufacturer specific data associated with the manufacturer id. Returns
* {@code null} if the {@code manufacturerId} is not found.
*/
@Nullable
public byte[] getManufacturerSpecificData(int manufacturerId) {
return mManufacturerSpecificData.get(manufacturerId);
}

/**
* Returns a map of service UUID and its corresponding service data.
*/
public Map<ParcelUuid, byte[]> getServiceData() {
return mServiceData;
}

/**
* Returns the service data byte array associated with the {@code serviceUuid}. Returns
* {@code null} if the {@code serviceDataUuid} is not found.
*/
@Nullable
public byte[] getServiceData(ParcelUuid serviceDataUuid) {
if (serviceDataUuid == n
d882
ull) {
return null;
}
return mServiceData.get(serviceDataUuid);
}

/**
* Returns the transmission power level of the packet in dBm. Returns {@link Integer#MIN_VALUE}
* if the field is not set. This value can be used to calculate the path loss of a received
* packet using the following equation:
* <p>
* <code>pathloss = txPowerLevel - rssi</code>
*/
public int getTxPowerLevel() {
return mTxPowerLevel;
}

/**
* Returns the local name of the BLE device. The is a UTF-8 encoded string.
*/
@Nullable
public String getDeviceName() {
return mDeviceName;
}

/**
* Returns raw bytes of scan record.
*/
public byte[] getBytes() {
return mBytes;
}

private ScanRecordUtil(List<ParcelUuid> serviceUuids,
SparseArray<byte[]> manufacturerData,
Map<ParcelUuid, byte[]> serviceData,
int advertiseFlags, int txPowerLevel,
String localName, byte[] bytes) {
mServiceUuids = serviceUuids;
mManufacturerSpecificData = manufacturerData;
mServiceData = serviceData;
mDeviceName = localName;
mAdvertiseFlags = advertiseFlags;
mTxPowerLevel = txPowerLevel;
mBytes = bytes;
}

/**
* Parse scan record bytes to {@link ScanRecord}.
* <p>
* The format is defined in Bluetooth 4.1 specification, Volume 3, Part C, Section 11 and 18.
* <p>
* All numerical multi-byte entities and values shall use little-endian <strong>byte</strong>
* order.
*
* @param scanRecord The scan record of Bluetooth LE advertisement and/or scan response.
* @hide
*/
public static ScanRecordUtil parseFromBytes(byte[] scanRecord) {
if (scanRecord == null) {
return null;
}

Log.e(TAG + "MYX23P", "进入parseFromBytes");
int currentPos = 0;
int advertiseFlag = -1;
List<ParcelUuid> serviceUuids = new ArrayList<ParcelUuid>();
String localName = null;
int txPowerLevel = Integer.MIN_VALUE;

SparseArray<byte[]> manufacturerData = new SparseArray<byte[]>();
Map<ParcelUuid, byte[]> serviceData = new ArrayMap<ParcelUuid, byte[]>();

try {
while (currentPos < scanRecord.length) {
// length is unsigned int.
int length = scanRecord[currentPos++] & 0xFF;
if (length == 0) {
break;
}
// Note the length includes the length of the field type itself.
int dataLength = length - 1;
// fieldType is unsigned int.
int fieldType = scanRecord[currentPos++] & 0xFF;
switch (fieldType) {
case DATA_TYPE_FLAGS:
advertiseFlag = scanRecord[currentPos] & 0xFF;
break;
case DATA_TYPE_SERVICE_UUIDS_16_BIT_PARTIAL:
case DATA_TYPE_SERVICE_UUIDS_16_BIT_COMPLETE:
parseServiceUuid(scanRecord, currentPos,
dataLength, MyBluetoothUuid.UUID_BYTES_16_BIT, serviceUuids);
break;
case DATA_TYPE_SERVICE_UUIDS_32_BIT_PARTIAL:
case DATA_TYPE_SERVICE_UUIDS_32_BIT_COMPLETE:
parseServiceUuid(scanRecord, currentPos, dataLength,
MyBluetoothUuid.UUID_BYTES_32_BIT, serviceUuids);
break;
case DATA_TYPE_SERVICE_UUIDS_128_BIT_PARTIAL:
case DATA_TYPE_SERVICE_UUIDS_128_BIT_COMPLETE:
parseServiceUuid(scanRecord, currentPos, dataLength,
MyBluetoothUuid.UUID_BYTES_128_BIT, serviceUuids);
break;
case DATA_TYPE_LOCAL_NAME_SHORT:
case DATA_TYPE_LOCAL_NAME_COMPLETE:
localName = new String(
extractBytes(scanRecord, currentPos, dataLength));
break;
case DATA_TYPE_TX_POWER_LEVEL:
txPowerLevel = scanRecord[currentPos];
break;
case DATA_TYPE_SERVICE_DATA:
// The first two bytes of the service data are service data UUID in little
// endian. The rest bytes are service data.
int serviceUuidLength = MyBluetoothUuid.UUID_BYTES_16_BIT;
byte[] serviceDataUuidBytes = extractBytes(scanRecord, currentPos,
serviceUuidLength);
ParcelUuid serviceDataUuid = MyBluetoothUuid.parseUuidFrom(
serviceDataUuidBytes);
byte[] serviceDataArray = extractBytes(scanRecord,
currentPos + serviceUuidLength, dataLength - serviceUuidLength);
serviceData.put(serviceDataUuid, serviceDataArray);
break;
case DATA_TYPE_MANUFACTURER_SPECIFIC_DATA:
// The first two bytes of the manufacturer specific data are
// manufacturer ids in little endian.
int manufacturerId = ((scanRecord[currentPos + 1] & 0xFF) << 8) +
(scanRecord[currentPos] & 0xFF);
byte[] manufacturerDataBytes = extractBytes(scanRecord, currentPos + 2,
dataLength - 2);
manufacturerData.put(manufacturerId, manufacturerDataBytes);
break;
default:
// Just ignore, we don't handle such data type.
break;
}
currentPos += dataLength;
}

if (serviceUuids.isEmpty()) {
serviceUuids = null;
}
return new ScanRecordUtil(serviceUuids, manufacturerData, serviceData,
advertiseFlag, txPowerLevel, localName, scanRecord);
} catch (Exception e) {
Log.e(TAG, "unable to parse scan record: " + Arrays.toString(scanRecord));
// As the record is invalid, ignore all the parsed results for this packet
// and return an empty record with raw scanRecord bytes in results
return new ScanRecordUtil(null, null, null, -1, Integer.MIN_VALUE, null, scanRecord);
}
}

@Override
public String toString() {
return "ScanRecord [mAdvertiseFlags=" + mAdvertiseFlags + ", mServiceUuids=" + mServiceUuids
+ ", mManufacturerSpecificData=" + MyBluetoothLeUtils.toString(mManufacturerSpecificData)
+ ", mServiceData=" + MyBluetoothLeUtils.toString(mServiceData)
+ ", mTxPowerLevel=" + mTxPowerLevel + ", mDeviceName=" + mDeviceName + "]";
}

// Parse service UUIDs.
private static int parseServiceUuid(byte[] scanRecord, int currentPos, int dataLength,
int uuidLength, List<ParcelUuid> serviceUuids) {
while (dataLength > 0) {
byte[] uuidBytes = extractBytes(scanRecord, currentPos,
uuidLength);
serviceUuids.add(MyBluetoothUuid.parseUuidFrom(uuidBytes));
dataLength -= uuidLength;
currentPos += uuidLength;
}
return currentPos;
}

// Helper method to extract bytes from byte array.
private static byte[] extractBytes(byte[] scanRecord, int start, int length) {
byte[] bytes = new byte[length];
System.arraycopy(scanRecord, start, bytes, 0, length);
return bytes;
}
}

这样采用它的核心解析广播的功能就得到了所有的信息。

小结

碰到问题时，仔细去找解决方法一定会解决的