active和passivescan的区别在于activescans 向广告商请求一个SCAN_RESPONSEpaket。这是通过SCAN_REQUEST在检测到广告后发送一个 paket 来完成的。两者的信息（有效负载）都将在scanRecord设备找到回调的参数中。
从核心规格：
设备可以使用主动扫描来获取有关可能对填充用户界面有用的设备的更多信息。主动扫描涉及更多的链路层广告消息。
因此，对于任何用例，这两种扫描类型之间都没有必要区分。
但是，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，以这个例子为例。但是扫描将在您的应用程序被系统杀死（或被用户停止）时结束。
通过 AlarmManager 启动 PendingIntent（在您的应用程序中的任何位置，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);
BleScan服务
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();
}
}
常量只是分配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多长时间......您可以根据需要轻松替换它。
然后您必须使用与上述动作名称匹配的意图过滤器注册广播接收器（BleServiceConstants.ACTION_DEVICE_DISCOVERED）
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
}
}