active和passive扫描之间的区别在于active扫描请求广告商提供SCAN_RESPONSE邮包.这是通过在检测到广告后发送SCAN_REQUEST小包来完成的.两者的信息(有效载荷)都将在找到的设备的scanRecord参数中回调.

The difference between active and passive scan is that active scans requests a SCAN_RESPONSE paket from the advertiser. This is done by sending a SCAN_REQUEST paket after an advertisements has been detected. The information (payload) of both will be in the scanRecord parameter of the device found callback.

来自核心规范:

设备可以使用主动扫描来获取有关设备的 更多信息 这对于填充用户界面可能很有用.主动扫描涉及更多 链接层广告消息.

A device may use active scanning to obtain more information about devices that may be useful to populate a user interface. Active scanning involves more link layer advertising messages.

因此，对于任何用例，都无需在这两种扫描类型之间进行区别.

So, for any usecase it will not be necessary to differ between those two scanning types.

但是，如果您想在后台收听广告，则需要通过创建Service来自己完成操作-没有内置功能(自Android 4.4起).

But if you want to listen for advertisements in the background then you need to do this yourself by creating a Service - there is no built in functionality (as of Android 4.4).

以背景扫描为例.但是扫描将在您的应用被系统杀死(或被用户停止)时结束.

For background scanning take this example. But the scan will end atthe point your app is killed by the system(or stopped by the user).

通过AlarmManager启动PendingIntent(在应用程序中的任何位置，必须至少运行一次以启动服务...)

Starting a PendingIntent through AlarmManager (anywhere in your app, that has to be run at least once to start the service...)

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

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();
    }
}

常量只是用于分配意图操作和附加名称的字符串.还有另一个首选项存储，用于存储扫描阶段应该持续多长时间...您可以根据需要轻松替换它.

The constants are just Strings to distribute the intent action and extra names. There is another preferences store that stores the how long the scanning phase should be...You can easily replace it ba your needs.

然后，您必须使用与上述动作名称(BleServiceConstants.ACTION_DEVICE_DISCOVERED)匹配的意图过滤器注册广播接收者

Then you have to registera broadcast reciever with an intent filter that matches the above action name (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

  }
}