Does Android Beacon Library really support background scanning?

问题

I am using Android Beacon Library for BLE scanning with example. It works fine in foreground for both monitoring and ranging. However, for background, it only works for the cases of pressing "Home" in app and screen off. It is not work when I kill the app from task switcher. In the example, I cannot find anything like Service to make things working in background.

Questions:

1. Does Android Beacon Library support background scanning if the app is killed in task switcher?
2. If so, how to do this? Any example?

回答1:

I worked with android iBeaon library in that for background scanning I created a service and in service I defined both monitoring and ranging. I start the service when application is distroy and its work for me. Create new service like this.

public class Beaconservice extends Service implements IBeaconConsumer {
private ArrayList<IBeacon> arrayL = new ArrayList<IBeacon>();
private BeaconServiceUtility beaconUtill = null;
private IBeaconManager iBeaconManager = IBeaconManager.getInstanceForApplication(this);
private Handler hand;
private Runnable runn;
private int count = 30;



@Override
public void onIBeaconServiceConnect() {
    iBeaconManager.setRangeNotifier(new RangeNotifier() {
        @Override
        public void didRangeBeaconsInRegion(Collection<IBeacon> iBeacons, Region region) {
            arrayL.clear();
            arrayL.addAll((ArrayList<IBeacon>) iBeacons);
            if(count>0){
                count=0;    
            }
        }
    });

    iBeaconManager.setMonitorNotifier(new MonitorNotifier() {
        @Override
        public void didEnterRegion(Region region) {
            Log.e("BeaconDetactorService", "didEnterRegion");
            // logStatus("I just saw an iBeacon for the first time!");
        }

        @Override
        public void didExitRegion(Region region) {
            Log.e("BeaconDetactorService", "didExitRegion");
            // logStatus("I no longer see an iBeacon");
        }

        @Override
        public void didDetermineStateForRegion(int state, Region region) {
            Log.e("BeaconDetactorService", "didDetermineStateForRegion");
            // logStatus("I have just switched from seeing/not seeing iBeacons: " + state);
        }

    });

    try {
        iBeaconManager.startRangingBeaconsInRegion(new Region("myRangingUniqueId", null, null, null));
    } catch (RemoteException e) {
        e.printStackTrace();
    }

    try {
        iBeaconManager.startMonitoringBeaconsInRegion(new Region("myMonitoringUniqueId", null, null, null));
    } catch (RemoteException e) {
        e.printStackTrace();
    }

}


@Override
public IBinder onBind(Intent arg0) {
    return null;
}
@Override
public void onCreate() {
    beaconUtill = new BeaconServiceUtility(this);
    Log.e("UUID","start service");

    hand = new Handler();
    runn = new Runnable() {

        @Override
        public void run() {
            count ++;
            hand.postDelayed(runn, 1000);
        }
    };

    hand.post(runn);
    super.onCreate();

}
@Override
@Deprecated
public void onStart(Intent intent, int startId) {
    beaconUtill.onStart(iBeaconManager, this);
    beaconUtill = new BeaconServiceUtility(this);
    super.onStart(intent, startId);
}
@Override
public void onDestroy() {
    beaconUtill.onStop(iBeaconManager, this);
    super.onDestroy();
}
}

In AndroidManifest.xml

 <service android:name="com.beacone.keyfinder.app.Beaconservice" >
 </service>

回答2:

Yes, the Android Beacon Library will continue detecting beacons after the app is killed, but it can take time for scanning to resume. See here for details: http://altbeacon.github.io/android-beacon-library/resume-after-terminate.html

The library uses an AlarmManager to accomplish this, and the scanning can take up to five minutes to resume.

The reference app you link to actually has an example of how to set this up using the RegionBootstrap class. A more descriptive example is in the code examples under the Starting an App in the Background section here: http://altbeacon.github.io/android-beacon-library/samples.html

回答3:

1. No, nor does any other app. Killing a task via Task Switcher means killing the process of that app, and since your background scan relies on a service, that service is killed too since services don't start their own process.

2. You can probably have an AlarmManager that periodically checks if your service is running and starts it automatically if it's not, but I'd imagine that would hit the battery big time if you set the interval too low.

来源：https://stackoverflow.com/questions/33513416/does-android-beacon-library-really-support-background-scanning