将 Object 从 Activity 传递到 Service，Object 无法实现 Serializable 或 Parcable

Question

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?

Answer 1

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 it like 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) {
            mServiceBinder = null;
        }

        @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);