I have an assignment for Android Development in Java, with the Google Maps api.

I have the Maps Activity and a separate location service that tracks the device's location, and i want to add a google maps tracker when the location of the device changes. I can do that if i pass the GoogleMap mMap object into the locationListener class i created:

public class LocationListener implements android.location.LocationListener
{
    private Location        cur_location;
    private LocationManager locationManager;
    private GoogleMap       mMap;
    
    @SuppressLint("MissingPermission")
    public LocationListener(LocationManager locationManager , GoogleMap mMap)
    {
        this.locationManager = locationManager;
        this.mMap            = mMap;
        this.cur_location    = getLastKnownLocation();
        
    }
    
    @SuppressLint("MissingPermission")
    private Location getLastKnownLocation() {
        List<String> providers = locationManager.getProviders(true);
        Location bestLocation = null;
        for (String provider : providers) {
            Location l = locationManager.getLastKnownLocation(provider);
            if (l == null) {
                continue;
            }
            if (bestLocation == null || l.getAccuracy() < bestLocation.getAccuracy()) {
                // Found best last known location: %s", l);
                bestLocation = l;
            }
        }
        return bestLocation;
    }
    
    @Override
    public void onLocationChanged(@NonNull Location location)
    {
        Log.e("LocationListener" , location.toString());
        cur_location = location;
        mMap.addMarker(new MarkerOptions().position(new LatLng(location.getLatitude() , location.getLongitude())).title("Marker"));
    }
    
    public Location getCur_location()
    {
        return cur_location;
    }
    
}

problem is that the LocationListener is initialised in the Service but the Location from the function getCur_location() needs to be accessed in the Activity therefore i need to pass the GoogleMap mMap object from the Activity to the Service.

The only way i know how to do that is through the Intent Extras , but the GoogleMap class doesn't implement Serializable nor Parcable.

Is there another way to pass an Object from an Activity to a Service ?

CodePudding user response：

I am assuming that the LocationListener is used within a Service class which you do not include in your question. You can achieve passing an object to the service if the service is a bound service. Check this documentation

Before proceeding explaining how, I want to note that something sounds wrong in this and needs deeper thought on how else you could avoid it

Within your service create a variable to hold the map object and then create an inner class extending the Binder and create an object of itlike below

    private GoogleMap mMap = null;
    private LocalBinder mBinder = new LocalBinder();
    public class LocalBinder extends Binder {
        public void setMap(GoogleMap map) {
            mMap = map;
        }
    }

Then make sure you clear the mMap when the service is not bound anymore

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

    @Override
    public void onRebind(Intent intent) {
        super.onRebind(intent);
    }

    @Override
    public boolean onUnbind(Intent intent) {
        mMap = null;
        return true;
    }

Now all you have to do is in your activity create a serviceConnection and bind to the service.

   private MyService.LocalBinder mServiceBinder = null;

   private final ServiceConnection mServiceConnection = new ServiceConnection() {

        @Override
        public void onServiceDisconnected(ComponentName name) {

        }

        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            mServiceBinder = (MyService.LocalBinder) service);
            // Now you can use the mServiceBinder to call setMap to pass your object to the service
        }
    };

You can bind anywhere you need (eg inside your onCreate) using the following code

Intent intent = new Intent(this, MyService.class);
boolean bound = getApplicationContext().bindService(intent, mServiceConnection, Context.BIND_AUTO_CREATE);