rapidclock's answer is fine. Personally I prefer using an IntentService because they're so wonderful. Also Google recommends it:
https://www.youtube.com/watch?v=xHXn3Kg2IQE&t=1852s
here's my IntentService:
// https://mcmap.net/q/867176/-android-volley-timeout-exception-when-using-requestfuture-get
//http://afzaln.com/volley/com/android/volley/toolbox/RequestFuture.html
//https://mcmap.net/q/905928/-android-synchronizing-methods-across-processes/36737001#36737001
// https://mcmap.net/q/159513/-can-i-do-a-synchronous-request-with-volley
package org.peacekeeper.service;
import android.app.IntentService;
import android.content.Intent;
import android.os.*;
import com.android.volley.RequestQueue;
import org.json.JSONObject;
import org.peacekeeper.app.R;
import org.peacekeeper.service.pkRequest.pkURL;
import org.peacekeeper.util.*;
import org.slf4j.*;
import java.util.concurrent.*;
/**
Asynchronously handles an intent using a worker thread. Receives a ResultReceiver object and a
location through an intent. Tries to fetch the address for the location using a Geocoder, and
sends the result to the ResultReceiver.
*/
public class RESTIntentService extends IntentService{
//begin static
//Intent putextra ID's
static public final String
RECEIVER = "RESTIntentServiceRCVR",
JSONResult = "JSONResult",
REQUEST = "RESTIntentServiceRequest";
protected final static pkUtility mUtility = pkUtility.getInstance();
protected final static RequestQueue mRequestQueue = mUtility.getRequestQueue();
private final static long TIMEOUT = 5;
//end static
private static final Logger mLog = LoggerFactory.getLogger( RESTIntentService.class );
//The receiver where results are forwarded from this service.
private ResultReceiver mReceiver;
//This constructor is required, and calls the super IntentService(String) constructor with the name for a worker thread.
public RESTIntentService(){ super( "RESTIntentService" ); }
@Override protected void onHandleIntent( Intent intent ){
String errorMessage = "";
mReceiver = intent.getParcelableExtra( RECEIVER );
if ( mReceiver == null ){// Check if receiver was properly registered.
mLog.error( "No RESTIntentService receiver received. There is nowhere to send the results." );
return;
}
// Get the pkRequest passed to this service through an extra.
pkRequest.pkURL URL = pkURL.valueOf( intent.getStringExtra( REQUEST ) );
mLog.debug( "RESTIntentService URL: " + URL.toString() );
// Make sure that the location data was really sent over through an extra. If it wasn't,
// send an error message and return.
if ( URL == null ){
errorMessage = getString( R.string.no_pkRequest_provided );
mLog.error( errorMessage );
deliverResultToReceiver( Constants.FAILURE_RESULT, errorMessage );
return;
}
//Request retval = null;
JSONObject response = null;
pkRequest request = new pkRequest( URL );
mLog.debug( "onHandleIntent:\n" + request.toString() );
request.submit();
try{
//while (!request.mFuture.isDone()) {;}
// TODO THIS BLOCKS the service but not the main UI thread. Consider wrapping in an asynch task:
// see https://mcmap.net/q/867176/-android-volley-timeout-exception-when-using-requestfuture-get
response = request.mFuture.get( TIMEOUT, TimeUnit.SECONDS );
mLog.debug( "onHandleIntent:\n" + response.toString() );
}catch ( InterruptedException | ExecutionException | TimeoutException x ){
errorMessage = getString( R.string.failed_future_request );
mLog.error( errorMessage, x );
x.printStackTrace();
}
if ( errorMessage.isEmpty() ){
deliverResultToReceiver( Constants.SUCCESS_RESULT,
response.toString() );
}
else{ deliverResultToReceiver( Constants.FAILURE_RESULT, errorMessage ); }
}//onHandleIntent()
// Sends a resultCode and message to the receiver.
private void deliverResultToReceiver( int resultCode, String message ){
Bundle bundle = new Bundle();
bundle.putString( JSONResult, message );
mReceiver.send( resultCode, bundle );
}
}//class RESTIntentService
The downside to using an IntentService is that IT (but not the main UI thread) will be blocked by the future.get(...). (see comment in code re: future.get block) So if you're blasting REST calls at it then you might consider still using it AND wrapping your calls in an async as recommended by rapidclock.
To use the above IntentService put this in the main UI (or whereever):
protected void startRESTService( final pkRequest.pkURL aURL ){
// Start the service. If the service isn't already running, it is instantiated and started
// (creating a process for it if needed); if it is running then it remains running. The
// service kills itself automatically once all intents are processed.
startService(
new Intent( this, RESTIntentService.class )
.putExtra( RESTIntentService.RECEIVER, mRESTResultReceiver )
.putExtra( RESTIntentService.REQUEST, aURL.name() )
);
}//startRESTService()
//Receiver for data sent from RESTIntentService.
class RESTResultReceiver extends ResultReceiver{
public RESTResultReceiver( Handler handler ){ super( handler ); }
//Receives data sent from RESTIntentService and updates the UI in MainActivity.
@Override protected void onReceiveResult( int resultCode, Bundle resultData ){
String snippet = resultData.getString( RESTIntentService.JSONResult );
mLog.debug( "RESTResultReceiver:\t" + snippet );
}//onReceiveResult
}//class RESTResultReceiver
oh alright...here's my activity (please don't ding me for being overly detailed...I love love love STACKOVERFLOW but no good deed goes unpunished....):
//https://mcmap.net/q/169184/-how-can-i-show-current-location-on-a-google-map-on-android-marshmallow/34582595#34582595
package org.peacekeeper.app;
import android.Manifest;
import android.content.*;
import android.content.pm.PackageManager;
import android.location.Location;
import android.os.*;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.*;
import android.widget.Toast;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.location.*;
import com.google.android.gms.maps.*;
import com.google.android.gms.maps.GoogleMap.*;
import com.google.android.gms.maps.model.*;
import com.google.android.gms.maps.model.Marker;
import org.json.JSONObject;
import org.peacekeeper.rest.LinkedRequest;
import org.peacekeeper.service.*;
import org.peacekeeper.service.pkRequest.pkURL;
import org.peacekeeper.util.pkUtility;
import org.slf4j.*;
import ch.qos.logback.classic.LoggerContext;
import ch.qos.logback.classic.util.ContextInitializer;
import ch.qos.logback.core.joran.spi.JoranException;
public class actGeocoder extends AppCompatActivity
implements OnMapReadyCallback,
GoogleApiClient.ConnectionCallbacks,
GoogleApiClient.OnConnectionFailedListener,
LocationListener,
OnMapLongClickListener,
OnMarkerClickListener{
//begin static
private static final LoggerContext mLoggerContext =
(LoggerContext) LoggerFactory.getILoggerFactory();
private static final ContextInitializer mContextInitializer =
new ContextInitializer( mLoggerContext );
private static final Logger mLog = LoggerFactory.getLogger( actGeocoder.class );
private static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;
//end static
private GoogleMap mGoogleMap;
private SupportMapFragment mapFrag;
private LocationRequest mLocationRequest;
private GoogleApiClient mGoogleApiClient;
private MarkerOptions mMarkerOptions;
private Marker mMarker;
private AddressResultReceiver mResultReceiver = new AddressResultReceiver( new Handler() );
private RESTResultReceiver mRESTResultReceiver = new RESTResultReceiver( new Handler() );
private pkUtility mUtility;
public void newPeaceKeeperStatus(){
startRESTService( pkRequest.pkURL.status );
}
@Override protected void onCreate( Bundle savedInstanceState ){
super.onCreate( savedInstanceState );
mUtility = pkUtility.getInstance( this );
newPeaceKeeperStatus();
setContentView( R.layout.geocoder );
getSupportActionBar().setTitle( R.string.RegisterYourLocn );
buildGoogleApiClient();
mapFrag = (SupportMapFragment) getSupportFragmentManager().findFragmentById( R.id.geocoder );
mapFrag.getMapAsync( this );
}//onCreate
@Override public void onResume(){
super.onResume();
mGoogleApiClient.connect();
}
@Override protected void onRestart(){
super.onRestart();
// Reload Logback log: https://mcmap.net/q/408218/-setting-logback-appender-path-programmatically/3810936#3810936
mLoggerContext.reset();
//I prefer autoConfig() over JoranConfigurator.doConfigure() so I don't need to find the file myself.
try{ mContextInitializer.autoConfig(); }
catch ( JoranException X ){ X.printStackTrace(); }
}//onRestart()
@Override protected void onStop(){
mGoogleApiClient.disconnect();
mLoggerContext.stop();//flush log
super.onStop();
}
@Override public void onDestroy(){
mLog.trace( "onDestroy():\t" );
mLoggerContext.stop();//flush log
super.onDestroy();
}
@Override public void onRequestPermissionsResult( int requestCode, String permissions[], int[] grantResults ){
switch ( requestCode ){
case MY_PERMISSIONS_REQUEST_LOCATION:{
// If request is cancelled, the result arrays are empty.
if ( grantResults.length > 0
&& grantResults[ 0 ] == PackageManager.PERMISSION_GRANTED ){
// permission was granted, yay! Do the location-related task you need to do.
if ( ContextCompat.checkSelfPermission( this,
Manifest.permission.ACCESS_FINE_LOCATION )
== PackageManager.PERMISSION_GRANTED ){
if ( mGoogleApiClient == null ){ buildGoogleApiClient(); }
mGoogleMap.setMyLocationEnabled( true );
}
}
// permission denied. Disable the functionality that depends on this permission.
else{ Toast.makeText( this, "permission denied", Toast.LENGTH_LONG ).show(); }
return;
}
}//switch
}
protected synchronized void buildGoogleApiClient(){
mGoogleApiClient = new GoogleApiClient.Builder( this )
.addConnectionCallbacks( this )
.addOnConnectionFailedListener( this )
.addApi( LocationServices.API )
.build();
mGoogleApiClient.connect();
}
//https://mcmap.net/q/905929/-android-google-maps-onmapready-store-googlemap
@Override public void onMapReady( GoogleMap googleMap ){
//Initialize Google Play Services
if ( Build.VERSION.SDK_INT >= Build.VERSION_CODES.M ){
if ( ContextCompat.checkSelfPermission( this,
Manifest.permission.ACCESS_FINE_LOCATION )
!= PackageManager.PERMISSION_GRANTED ){
//Location Permission already granted
checkLocationPermission();
return; //Request Location Permission
}
}
mGoogleMap = googleMap;
mGoogleMap.setMapType( GoogleMap.MAP_TYPE_NORMAL );
mGoogleMap.setOnMapLongClickListener( this );
mGoogleMap.setOnMarkerClickListener(this);
mMarkerOptions = new MarkerOptions()
.title( "Tap this marker again to register your location" )
.icon( BitmapDescriptorFactory.defaultMarker( BitmapDescriptorFactory.HUE_MAGENTA) );
}
private void checkLocationPermission(){
if ( ContextCompat.checkSelfPermission( this, Manifest.permission.ACCESS_FINE_LOCATION )
!= PackageManager.PERMISSION_GRANTED ){
// Should we show an explanation?
if ( ActivityCompat.shouldShowRequestPermissionRationale( this,
Manifest.permission.ACCESS_FINE_LOCATION ) ){
// Show an explanation to the user *asynchronously* -- don't block this thread waiting for the user's response!
// After the user sees the explanation, try again to request the permission.
new AlertDialog.Builder( this )
.setTitle( "Location Permission Needed" )
.setMessage(
"This app needs the Location permission, please accept to use location functionality" )
.setPositiveButton( "OK", new DialogInterface.OnClickListener(){
@Override public void onClick( DialogInterface dialogInterface, int i ){
//Prompt the user once explanation has been shown
ActivityCompat.requestPermissions( actGeocoder.this,
new String[]{ Manifest.permission.ACCESS_FINE_LOCATION },
MY_PERMISSIONS_REQUEST_LOCATION );
}
} )
.create()
.show(); }
else{ // No explanation needed, we can request the permission.
ActivityCompat.requestPermissions( this,
new String[]{ Manifest.permission.ACCESS_FINE_LOCATION },
MY_PERMISSIONS_REQUEST_LOCATION );
}
}
}
@Override public void onConnected( Bundle bundle ){
mLocationRequest = new LocationRequest()
.setInterval( 1000 )
.setFastestInterval( 1000 )
.setPriority( LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY );
if ( ContextCompat.checkSelfPermission( this, Manifest.permission.ACCESS_FINE_LOCATION )
== PackageManager.PERMISSION_GRANTED ){
LocationServices.FusedLocationApi.
requestLocationUpdates( mGoogleApiClient, mLocationRequest, this );
}
}
private final static float ZOOM = 18;
@Override public void onLocationChanged( Location location ){//this is called only once on startup.
//stop location updates since only current location is needed
LocationServices.FusedLocationApi
.removeLocationUpdates( mGoogleApiClient, this );
LatLng latLng = new LatLng( location.getLatitude(), location.getLongitude() );
mGoogleMap.moveCamera( CameraUpdateFactory.newLatLngZoom( latLng, ZOOM ) );
onMapLongClick(latLng);
}
@Override public void onMapLongClick( final LatLng latLng ){
startIntentService( latLng );
if ( mMarker != null ) mMarker.remove();
mMarkerOptions.position( latLng );
mMarker = mGoogleMap.addMarker( mMarkerOptions );
}//onMapLongClick
@Override public boolean onMarkerClick( Marker marker) {
startActivity(
new Intent(this, actRegistration.class)
.putExtra( FetchAddressIntentService.LOCATION, marker.getSnippet() )
.putExtra( FetchAddressIntentService.LATLNG, marker.getPosition() )
);
return true;
}//onMarkerClick
protected void startIntentService( final LatLng latLng ){
// Start the service. If the service isn't already running, it is instantiated and started
// (creating a process for it if needed); if it is running then it remains running. The
// service kills itself automatically once all intents are processed.
startService(
new Intent( this, FetchAddressIntentService.class )
.putExtra( FetchAddressIntentService.RECEIVER, mResultReceiver )
.putExtra( FetchAddressIntentService.LATLNG, latLng )
);
}//startIntentService()
protected void startRESTService( final pkRequest.pkURL aURL ){
// Start the service. If the service isn't already running, it is instantiated and started
// (creating a process for it if needed); if it is running then it remains running. The
// service kills itself automatically once all intents are processed.
startService(
new Intent( this, RESTIntentService.class )
.putExtra( RESTIntentService.RECEIVER, mRESTResultReceiver )
.putExtra( RESTIntentService.REQUEST, aURL.name() )
);
}//startRESTService()
//Receiver for data sent from FetchAddressIntentService.
class AddressResultReceiver extends ResultReceiver{
public AddressResultReceiver( Handler handler ){ super( handler ); }
//Receives data sent from FetchAddressIntentService and updates the UI in MainActivity.
@Override protected void onReceiveResult( int resultCode, Bundle resultData ){
mMarker.setSnippet( resultData.getString( FetchAddressIntentService.LOCATION ) );
mMarker.showInfoWindow();
}//onReceiveResult
}//class AddressResultReceiver
//Receiver for data sent from RESTIntentService.
class RESTResultReceiver extends ResultReceiver{
public RESTResultReceiver( Handler handler ){ super( handler ); }
//Receives data sent from RESTIntentService and updates the UI in MainActivity.
@Override protected void onReceiveResult( int resultCode, Bundle resultData ){
String snippet = resultData.getString( RESTIntentService.JSONResult );
mLog.debug( "RESTResultReceiver:\t" + snippet );
}//onReceiveResult
}//class RESTResultReceiver
@Override public void onConnectionSuspended( int i ){ mLog.info("onConnectionSuspended: " + i );}
@Override public void onConnectionFailed( ConnectionResult connectionResult ){
mLog.error( R.string.GoogleApiClientConnFailed + ":\t" + connectionResult.getErrorMessage() );
Toast.makeText(this, R.string.GoogleApiClientConnFailed, Toast.LENGTH_LONG).show();
}
}//class actGeocoder