Making the code in an Activity into a Service difficulties

Question

How can I modify this Activity to a Service, I want to be able to call this service from another Activity and for it to be able to work in background even when the user isn't actually in the app. When I tried to convert it into a Service I had problems with onResume(), onStart(), onStop() and finish(). How can I fix that? This is the code as an Activity:

public class MainActivity extends Activity implements ConnectionCallbacks,
    OnConnectionFailedListener, LocationListener {

// LogCat tag
private static final String TAG = MainActivity.class.getSimpleName();

private final static int PLAY_SERVICES_RESOLUTION_REQUEST = 1000;

private Location mLastLocation;

// Google client to interact with Google API
private GoogleApiClient mGoogleApiClient;

// boolean flag to toggle periodic location updates
private boolean mRequestingLocationUpdates = false;

private LocationRequest mLocationRequest;

// Location updates intervals in sec
private static int UPDATE_INTERVAL = 10000; // 10 sec
private static int FATEST_INTERVAL = 5000; // 5 sec
private static int DISPLACEMENT = 10; // 10 meters

// UI elements
private TextView lblLocation;
private Button btnShowLocation, btnStartLocationUpdates;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    lblLocation = (TextView) findViewById(R.id.lblLocation);
    btnShowLocation = (Button) findViewById(R.id.btnShowLocation);
    btnStartLocationUpdates = (Button) findViewById(R.id.btnLocationUpdates);

    // First we need to check availability of play services
    if (checkPlayServices()) {

        // Building the GoogleApi client
        buildGoogleApiClient();

        createLocationRequest();
    }

    // Show location button click listener
    btnShowLocation.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            displayLocation();
        }
    });

    // Toggling the periodic location updates
    btnStartLocationUpdates.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            togglePeriodicLocationUpdates();
        }
    });

}

@Override
protected void onStart() {
    super.onStart();
    if (mGoogleApiClient != null) {
        mGoogleApiClient.connect();
    }
}

@Override
protected void onResume() {
    super.onResume();

    checkPlayServices();

    // Resuming the periodic location updates
    if (mGoogleApiClient.isConnected() && mRequestingLocationUpdates) {
        startLocationUpdates();
    }
}

@Override
protected void onStop() {
    super.onStop();
    if (mGoogleApiClient.isConnected()) {
        mGoogleApiClient.disconnect();
    }
}

@Override
protected void onPause() {
    super.onPause();
    stopLocationUpdates();
}

/**
 * Method to display the location on UI
 * */
private void displayLocation() {

    mLastLocation = LocationServices.FusedLocationApi
            .getLastLocation(mGoogleApiClient);

    if (mLastLocation != null) {
        double latitude = mLastLocation.getLatitude();
        double longitude = mLastLocation.getLongitude();

        lblLocation.setText(latitude + ", " + longitude);

    } else {

        lblLocation
                .setText("(Couldn't get the location. Make sure location is enabled on the device)");
    }
}

/**
 * Method to toggle periodic location updates
 * */
private void togglePeriodicLocationUpdates() {
    if (!mRequestingLocationUpdates) {
        // Changing the button text
        btnStartLocationUpdates
                .setText(getString(R.string.btn_stop_location_updates));

        mRequestingLocationUpdates = true;

        // Starting the location updates
        startLocationUpdates();

        Log.d(TAG, "Periodic location updates started!");

    } else {
        // Changing the button text
        btnStartLocationUpdates
                .setText(getString(R.string.btn_start_location_updates));

        mRequestingLocationUpdates = false;

        // Stopping the location updates
        stopLocationUpdates();

        Log.d(TAG, "Periodic location updates stopped!");
    }
}

/**
 * Creating google api client object
 * */
protected synchronized void buildGoogleApiClient() {
    mGoogleApiClient = new GoogleApiClient.Builder(this)
            .addConnectionCallbacks(this)
            .addOnConnectionFailedListener(this)
            .addApi(LocationServices.API).build();
}

/**
 * Creating location request object
 * */
protected void createLocationRequest() {
    mLocationRequest = new LocationRequest();
    mLocationRequest.setInterval(UPDATE_INTERVAL);
    mLocationRequest.setFastestInterval(FATEST_INTERVAL);
    mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
    mLocationRequest.setSmallestDisplacement(DISPLACEMENT);
}

/**
 * Method to verify google play services on the device
 * */
private boolean checkPlayServices() {
    int resultCode = GooglePlayServicesUtil
            .isGooglePlayServicesAvailable(this);
    if (resultCode != ConnectionResult.SUCCESS) {
        if (GooglePlayServicesUtil.isUserRecoverableError(resultCode)) {
            GooglePlayServicesUtil.getErrorDialog(resultCode, this,
                    PLAY_SERVICES_RESOLUTION_REQUEST).show();
        } else {
            Toast.makeText(getApplicationContext(),
                    "This device is not supported.", Toast.LENGTH_LONG)
                    .show();
            finish();
        }
        return false;
    }
    return true;
}

/**
 * Starting the location updates
 * */
protected void startLocationUpdates() {

    LocationServices.FusedLocationApi.requestLocationUpdates(
            mGoogleApiClient, mLocationRequest, this);

}

/**
 * Stopping location updates
 */
protected void stopLocationUpdates() {
    LocationServices.FusedLocationApi.removeLocationUpdates(
            mGoogleApiClient, this);
}

/**
 * Google api callback methods
 */
@Override
public void onConnectionFailed(ConnectionResult result) {
    Log.i(TAG, "Connection failed: ConnectionResult.getErrorCode() = "
            + result.getErrorCode());
}

@Override
public void onConnected(Bundle arg0) {

    // Once connected with google api, get the location
    displayLocation();

    if (mRequestingLocationUpdates) {
        startLocationUpdates();
    }
}

@Override
public void onConnectionSuspended(int arg0) {
    mGoogleApiClient.connect();
}

@Override
public void onLocationChanged(Location location) {
    // Assign the new location
    mLastLocation = location;

    Toast.makeText(getApplicationContext(), "Location changed!",
            Toast.LENGTH_SHORT).show();

    // Displaying the new location on UI
    displayLocation();
}

Answer 1

You need to read up on Services. They have a different lifecycle. Finish doesn't exist. OnPause, OnResume, etc don't exist. The lifecycle is explained at http://developer.android.com/reference/android/app/Service.html. Start reading there.