我想在我的Android应用中被动地扫描BLE广告客户 但我找不到如何做到这一点。
根据蓝牙4.0核心规范，存在被动扫描模式
第6卷：核心系统包[低能量控制器容量]，
D部分：4.1被动扫描
https://www.bluetooth.org/DocMan/handlers/DownloadDoc.ashx?doc_id=282159
“设备可以使用被动扫描在该区域内找到广告设备。”
而且，android有决定扫描类型的参数。 （主动/被动）
http://androidxref.com/4.3_r2.1/xref/external/bluetooth/bluedroid/stack/btm/btm_ble_gap.c#555
“scan_type：主动扫描或被动扫描”
同时，iOS可以被动地扫描广告客户。 （遗憾的是，只有背景模式）
http://lists.apple.com/archives/bluetooth-dev/2012/May/msg00041.html
“当应用程序处于后台时，iOS会执行被动扫描。”
但我无法找到是否可以使用被动扫描模式。
问题：是否可以在Android上使用“PASSIVE SCAN”？如果可能，如何使用此功能？
答案 0 :(得分：14)
active和passive次扫描之间的区别在于active扫描请求广告客户SCAN_RESPONSE paket。这是通过在检测到广告后发送SCAN_REQUEST paket来完成的。两者的信息（有效载荷）将位于设备找到的回调的scanRecord参数中。
来自core spec：
设备可能会使用主动扫描来获取有关设备的 更多信息 这可能对填充用户界面很有用。主动扫描涉及更多 链接层广告信息。
因此，对于任何用例，没有必要区分这两种扫描类型。
但如果您想在后台收听广告，那么您需要自己创建一个Service - 没有内置功能（从Android 4.4开始）。
对于后台扫描，请参考此示例。但是扫描将在您的应用程序被系统杀死（或由用户停止）点结束。
通过AlarmManager启动PendingIntent（在您的应用中的任何位置，必须至少运行一次才能启动服务...）
AlarmManager alarmMgr = (AlarmManager) getActivity().getSystemService(Context.ALARM_SERVICE);
Intent intent = new Intent(getActivity(), BleScanService.class);
PendingIntent scanIntent = PendingIntent.getService(getActivity(), 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
alarmMgr.setRepeating(AlarmManager.RTC_WAKEUP, SystemClock.elapsedRealtime(), intervalMillis, scanIntent);
BleScanService
public class BleScanService extends Service implements LeScanCallback {
private final static String TAG = BleScanService.class.getSimpleName();
private final IBinder mBinder = new LocalBinder();
private BluetoothManager mBluetoothManager;
private BluetoothAdapter mBluetoothAdapter;
public class LocalBinder extends Binder {
public BleScanService getService() {
return BleScanService.this;
}
}
@Override
public IBinder onBind(Intent intent) {
return mBinder;
}
@Override
public boolean onUnbind(Intent intent) {
return super.onUnbind(intent);
}
@Override
public void onCreate() {
super.onCreate();
initialize();
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
long timeToScan = preferences.scanLength().get();
startScan(timeToScan);
return super.onStartCommand(intent, flags, startId);
}
/**
* Initializes a reference to the local bluetooth adapter.
*
* @return Return true if the initialization is successful.
*/
public boolean initialize() {
// For API level 18 and above, get a reference to BluetoothAdapter
// through
// BluetoothManager.
if (mBluetoothManager == null) {
mBluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
if (mBluetoothManager == null) {
Log.e(TAG, "Unable to initialize BluetoothManager.");
return false;
}
}
if (mBluetoothAdapter == null) {
mBluetoothAdapter = mBluetoothManager.getAdapter();
if (mBluetoothAdapter == null) {
Log.e(TAG, "Unable to obtain a BluetoothAdapter.");
return false;
}
}
Log.d(TAG, "Initialzed scanner.");
return true;
}
/**
* Checks if bluetooth is correctly set up.
*
* @return
*/
protected boolean isInitialized() {
return mBluetoothManager != null && mBluetoothAdapter != null && mBluetoothAdapter.isEnabled();
}
/**
* Checks if ble is ready and bluetooth is correctly setup.
*
* @return
*/
protected boolean isReady() {
return isInitialized() && isBleReady();
}
/**
* Checks if the device is ble ready.
*
* @return
*/
protected boolean isBleReady() {
return getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE);
}
@Override
public void onLeScan(BluetoothDevice device, int rssi, byte[] scanRecord) {
Log.d(TAG, "Found ble device " + device.getName() + " " + device.getAddress());
broadcastOnDeviceFound(device, scanRecord);
}
/**
* Broadcasts a message with the given device.
*
* @param device
* @param scanRecord
*/
protected void broadcastOnDeviceFound(final BluetoothDevice device, byte[] scanRecord) {
assert device != null : "Device should not be null.";
Intent intent = new Intent(BleServiceConstants.ACTION_DEVICE_DISCOVERED);
intent.putExtra(BleServiceConstants.EXTRA_DEVICE_DISCOVERED_DEVICE, device);
intent.putExtra(BleServiceConstants.EXTRA_DEVICE_DISCOVERED_SCAN_RECORD, scanRecord);
sendBroadcast(intent);
}
/**
* Starts the bluetooth low energy scan It scans at least the
* delayStopTimeInMillis.
*
* @param delayStopTimeInMillis
* the duration of the scan
* @return <code>true</code> if the scan is successfully started.
*/
public boolean startScan(long delayStopTimeInMillis) {
if (!isReady())
return false;
if (preferences.shouldScan().get()) {
if (delayStopTimeInMillis <= 0) {
Log.w(TAG, "Did not start scanning with automatic stop delay time of " + delayStopTimeInMillis);
return false;
}
Log.d(TAG, "Auto-Stop scan after " + delayStopTimeInMillis + " ms");
getMainHandler().postDelayed(new Runnable() {
@Override
public void run() {
Log.d(TAG, "Stopped scan.");
stopScan();
}
}, delayStopTimeInMillis);
}
return startScan();
}
/**
* @return an handler with the main (ui) looper.
*/
private Handler getMainHandler() {
return new Handler(getMainLooper());
}
/**
* Starts the bluetooth low energy scan. It scans without time limit.
*
* @return <code>true</code> if the scan is successfully started.
*/
public boolean startScan() {
if (!isReady())
return false;
if (preferences.shouldScan().get()) {
if (mBluetoothAdapter != null) {
Log.d(TAG, "Started scan.");
return mBluetoothAdapter.startLeScan(this);
} else {
Log.d(TAG, "BluetoothAdapter is null.");
return false;
}
}
return false;
}
/**
* Stops the bluetooth low energy scan.
*/
public void stopScan() {
if (!isReady())
return;
if (mBluetoothAdapter != null)
mBluetoothAdapter.stopLeScan(this);
else {
Log.d(TAG, "BluetoothAdapter is null.");
}
}
@Override
public void onDestroy() {
preferences.edit().shouldScan().put(false).apply();
super.onDestroy();
}
}
常量只是用于分发意图操作和额外名称的字符串。还有另一个首选项存储，存储扫描阶段应该是多长时间......您可以根据需要轻松替换它。
然后你必须使用与上述动作名称匹配的意图过滤器（BleServiceConstants.ACTION_DEVICE_DISCOVERED）注册广播接收器
public class DeviceWatcher extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
BluetoothDevice device = intent.getParcelableExtra(BleServiceConstants.EXTRA_DEVICE_DISCOVERED_DEVICE);
// do anything with this information
}
}