How to detect headphone plug event in "offline" mode [closed]

Question

I know how to detect headphone plug in event if my application is running. You have to register broadcast receiver for ACTION_HEADSET_PLUG. But you can't capture this action using Manifest declaration for broadcast receiver. Therefore the only option to capture headphone plug in event is background service. But it drains battery and so on.

I checked out some music players and figured out that they capture that event without any additional services. How do they do that? Any ideas?

Answer 1

I've had an app in the store for three years that monitors both the wired headset and bluetooth state and nobody has ever complained about battery drain. But that is because I am successfully using a single service and broadcast receiver for detecting events from both. Here's the two key classes:

public class HeadsetStateBroadcastReceiver extends BroadcastReceiver {

    public static final String[] HEADPHONE_ACTIONS = {
        Intent.ACTION_HEADSET_PLUG,
        "android.bluetooth.headset.action.STATE_CHANGED",
        "android.bluetooth.headset.profile.action.CONNECTION_STATE_CHANGED"
    };

    @Override
    public void onReceive(final Context context, final Intent intent) {

        boolean broadcast = false;

        // Wired headset monitoring
        if (intent.getAction().equals(HEADPHONE_ACTIONS[0]) {
            final int state = intent.getIntExtra("state", 0);
            AudioPreferences.setWiredHeadphoneState(context, state > 0);
            broadcast = true;
        }

        // Bluetooth monitoring
        // Works up to and including Honeycomb
        if (intent.getAction().equals(HEADPHONE_ACTIONS[1])) {
            int state = intent.getIntExtra("android.bluetooth.headset.extra.STATE", 0);
            AudioPreferences.setBluetoothHeadsetState(context, state == 2);
            broadcast = true;
        }

        // Works for Ice Cream Sandwich
        if (intent.getAction().equals(HEADPHONE_ACTIONS[2])) {
            int state = intent.getIntExtra("android.bluetooth.profile.extra.STATE", 0);
            AudioPreferences.setBluetoothHeadsetState(context, state == 2);
            broadcast = true;
        }

        // Used to inform interested activities that the headset state has changed
        if (broadcast) {
            LocalBroadcastManager.getInstance(context).sendBroadcast(new Intent("headsetStateChange"));
        }

    }

}

Here is the service I use to register the broadcast receiver:

public class HeadsetMonitoringService extends Service {

    HeadsetStateBroadcastReceiver headsetStateReceiver;

    @Override
    public void onCreate() {

        headsetStateReceiver = new HeadsetStateBroadcastReceiver();
        final IntentFilter filter = new IntentFilter();
        for (String action: HeadsetStateBroadcastReceiver.HEADPHONE_ACTIONS) {
            filter.addAction(action);
        }

        registerReceiver(headsetStateReceiver, filter);

    }

    @Override
    public int onStartCommand(final Intent intent, final int flags, final int startId) {
        return START_STICKY;
    }

    @Override
    public void onDestroy() {
        unregisterReceiver(headsetStateReceiver);
    }

    @Override
    public IBinder onBind(final Intent intent) {
        return null;
    }

}

And here is my manifest entry:

    <service
        android:name=".services.HeadsetMonitoringService"
        android:enabled="true"
        android:exported="false" >
        <intent-filter>
            <action android:name="initialiseHeadsetService" />
        </intent-filter>
    </service>

How it works is as follows:

I use an on boot broadcast receiver to send a start service message to the HeadsetMonitoringService (you don't have to do it this way, you could just do this when your application starts instead). The HeadsetMonitoringService in turn registers an instance of a broadcast listener that listens to all the headset events I am interested in - they are held in the HEADPHONE_ACTIONS array. Because the service is sticky it hangs around - and therefore so does the broadcast listener. But because both the service and the broadcast listener are event driven they do not consume any power until a headset state change occurs. Additionally, because the service is sticky, it will be restarted by the OS if it dies unexpectedly.
Whenever I receive a headset state change event I also fire a local broadcast so that interested activities can check the new state and take action if required.

For completeness, I should point out that I use another class (not shown here), AudioPreferences, to store as preferences both the Bluetooth and wired headset state, which can then be accessed whenever I need to know the headset state.

Your application will need the android.permission.BLUETOOTH permission if you are interested in the state of a Bluetooth headset. If not, just take out the Bluetooth related actions from the HEADPHONE_ACTIONS array and delete the associated if blocks from the onReceive method.