Develop Reference

Communication between Android Services and Activities

I want to develop an Android App with three activities and two services.
The first Service, named WebClientService, calls a REST API every 30 seconds, using an Handler, and has to notify the active Activity with the result.
It also has to notify a second Service, named DatabaseService, in order to update a local DB.
The Database Service will be called just once onCreate of the activity (in case of app crash and restart) and just once at onRestart (in this way we have data to show in case there were connectivity issues). The activities will then keep themselves updated thanks to the WebClientService that notifies the "alive" activity every 30 seconds.
Questions are:
What's the best way to notify for an update both the active activity and the background DatabaseService?
My idea is to use sendBroadcast() within WebClientService and a BroadcastReceiver in every activity and within the DatabaseService, is it the right approach?
Should I use the same approach for the communication between AllMeetingRoomActivity and DatabaseService or should I use a Bound Service?
Thanks
UPDATE:
DatabaseService won't be a background service anymore but just a shared instance of the db layer between WebClientService and the activities.
So question now is: is it a good approach to just write my 30 seconds updates to the local db and allow the activities to update themselves every few seconds simply reading from the local db?
Would that affect the performance too much?
Context:
Follows what I've implemented so far but using SettableFutures and thus needs to be re-implemented using Services and Broadcasts once I've clear how to make them communicate effectively:
public class MainActivity extends AppCompatActivity {
private TextView meetingsTextView;
private EditText mEdit, editSubject;
private final ConnectorInitializer clientInitializer = new ConnectorInitializer();
private AppConnector genericClient; // can use OutlookClient or a test client to talk with a mock server
#Override
protected void onCreate(Bundle savedInstanceState) {
// initializes client based on the settings in "config.json"
genericClient = clientInitializer.create(this);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
meetingsTextView = (TextView) findViewById(R.id.NowMeeting);
mEdit = (EditText)findViewById(R.id.editText);
editSubject = (EditText)findViewById(R.id.editSubject);
Futures.addCallback(genericClient.logon(this, scopes), new FutureCallback<Boolean>() {
#Override
public void onSuccess(Boolean result) {
Log.d("APP", "-- Logged in. --");
databaseConnector.synchronouslyGetBackupFromLocalDatabase() // FUTURE
// callback here
// onSuccess, onFailure
}
#Override
public void onFailure(#NonNull Throwable t) {
Log.e("\n ~~~~>> logon \n", t.getMessage());
meetingsTextView.setText(R.string.Login_Failed);
}
});
}
/** At the moment the UI is not updated automatically every 30 seconds
* but manually using a refresh button
*/
public void getBookings(#SuppressWarnings("UnusedParameters") View view){
Log.d("APP", "Retrieve button clicked: "+(DateTime.now())+". Calling async getCalendar.");
meetingsTextView.setText(R.string.retrieving_events);
try{
Futures.addCallback( genericClient.getCalendarEvents(), new FutureCallback<String>(){
#Override
public void onSuccess(final String resultCalendars) {
Log.d("APP", "Success. Result: "+resultCalendars);
runOnUiThread(new Runnable() {
#Override
public void run() {
Log.d("APP", "Calendars SUCCESSFULLY retrieved.");
String meetingsRetrieved = getString(R.string.calendar)+resultCalendars;
meetingsTextView.setText(meetingsRetrieved);
Toast.makeText(getApplicationContext(), "Success!", Toast.LENGTH_LONG).show();
}
});
databaseConnector.asyncUpdateLocalDbWithResults(); // FUTURE
// callback here
// onSuccess, onFailure
}
#Override
public void onFailure(#NonNull Throwable t) {
Log.e( "APP", "Calendar error. Cause: "+t.getLocalizedMessage() );
String retrieveError = "Retrieve error. \n\n\n"+t.getLocalizedMessage();
meetingsTextView.setText(retrieveError);
Toast.makeText(getApplicationContext(), "Fail!", Toast.LENGTH_LONG).show();
}
});
}catch(Exception ex){
Log.e("APP","Something went wrong in your code. Cause:"+ex);
}
}

Best option ever:
Use LocalBroadcastManager. More reference here.
MyService.java:
private LocalBroadcastManager localBroadcastManager;
private final String SERVICE_RESULT = "com.service.result";
private final String SERVICE_MESSAGE = "com.service.message";
#Override
public void onCreate() {
super.onCreate();
// Other stuff
localBroadcastManager = LocalBroadcastManager.getInstance(this);
}
Add below method in service, whenever you want to update data from service to Activity, call method by passing Arguments.
private void sendResult(String message) {
Intent intent = new Intent(SERVICE_RESULT);
if(message != null)
intent.putExtra(SERVICE_MESSAGE, message);
localBroadcastManager.sendBroadcast(intent);
}
HomeActivity.java:
private BroadcastReceiver broadcastReceiver;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
super.setContentView(R.layout.activity_home);
broadcastReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
String s = intent.getStringExtra(MyService.SERVICE_MESSAGE);
// do something here.
}
};
}
#Override
protected void onStart() {
super.onStart();
LocalBroadcastManager.getInstance(this).registerReceiver((broadcastReceiver),
new IntentFilter(MyService.SERVICE_RESULT));
}
#Override
protected void onStop() {
LocalBroadcastManager.getInstance(this).unregisterReceiver(broadcastReceiver);
super.onStop();
}
Hope this will help you.

I think your approach is ok with BroadCastReceiver. However, BroadCastReceiver should be used for a global purpose (like communicating between 2 applications). If you intend to use BroadCastReceiver for your app only, I prefer using LocalBroadcastManager instead. Using LocalBroadcastManager is faster and more security when it can be caught only by your app.
There's another way to communicate between your activitys and your services is using EventBus. It will be much easier than using BroadCastReceiver (especially in passing data between them).
Update: About your update question:
is it a good approach to just write my 30 seconds updates to the local db and allow the activities to update themselves every few seconds simply reading from the local db? --> Of course NO. You should let your activities update themselves when they need. When you update your local db, you should know that is there any changes or not. If there is any change, use LocalBroadcastmanager to notify your activity to update.
Would that affect the performance too much? --> Yes, that do. The db connection will take time to execute and it will block your UI in some cases. in that case, you should use a thread with ExecutorService for each execute (insert, update...). One more thing to consider is updating that frequently will drain your phone battery very, very fast.

You can bind the services to the activities and update your UI.
Or you can use libraries like Otto or EventBus to create a publisher/subscriber dependency and notify your activities everytime your services publish an update of information.

Use event bus for this communication. EventBus allows publish-subscribe-style communication between components without requiring the components to explicitly register with one another (and thus be aware of each other). It is designed exclusively to replace traditional Java in-process event distribution using explicit registration.
There are a lot of them:
http://square.github.io/otto/
https://github.com/greenrobot/EventBus
This is an example of Otto usage:
Bus bus = new Bus();
bus.post(new AnswerAvailableEvent(42));
#Subscribe public void answerAvailable(AnswerAvailableEvent event) {
// TODO: React to the event somehow!
}
bus.register(this); // In order to receive events, a class instance needs to register with the bus.
To post from any thread (main or background), in you case a Service and receive events on the main thread:
public class MainThreadBus extends Bus {
private final Handler mHandler = new Handler(Looper.getMainLooper());
#Override
public void post(final Object event) {
if (Looper.myLooper() == Looper.getMainLooper()) {
super.post(event);
} else {
mHandler.post(new Runnable() {
#Override
public void run() {
MainThreadBus.super.post(event);
}
});
}
}

BroadcastReceiver - Can't get button to change background

I have an Activity and a Service.
In my Activity, a button interacts with the Service to start/stop GPS logging.
My Service has 3 state indicators: One for being connected to Google Play Services, one for actively logging GPS, and one for processing what was logged.
When connected to Google Play Services the Service flow is this:
Ready -> Logging -> Processing -> Ready
The Service will broadcast these states as follows:
private void UpdateStatusBroadcast() {
//Save status variables to intent
Intent intent = new Intent(this.getString(R.string.BroadcastStatusIntent));
intent.putExtra(getString(R.string.BroadcastIsConnected), mIsConnected);
intent.putExtra(getString(R.string.BroadcastIsTripActive), mIsTripActive);
intent.putExtra(getString(R.string.BroadcastIsProcessing), mIsProcessing);
//Send the broadcast
LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
}
My Activity receives the states as follows:
private class StatusReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
mIsConnected = intent.getBooleanExtra(getString(R.string.BroadcastIsConnected), false);
mIsTripActive = intent.getBooleanExtra(getString(R.string.BroadcastIsTripActive), false);
mIsProcessing = intent.getBooleanExtra(getString(R.string.BroadcastIsProcessing), false);
HandleConnectionStatus();
HandleTripStatus();
}
}
Then comes my problem. In HandleTripStatus(), posted below, i change the text and background of a button to reflect what the Service is currently doing. This works fine for the first and the third case. I never see the second background drawn however, in spite of receiving the correct boolean values.
private void HandleTripStatus() {
Button tripButton = (Button) findViewById(R.id.TripButton);
Button liveMapButton = (Button) findViewById(R.id.LiveMapButton);
if (mIsTripActive) {
tripButton.setText(R.string.TripButtonTitleStop);
tripButton.setBackground(ContextCompat.getDrawable(mContext, R.drawable.trip_button_stop_shape));
liveMapButton.setEnabled(true);
} else if (mIsProcessing) {
tripButton.setText(R.string.TripButtonTitleStopping);
tripButton.setBackground(ContextCompat.getDrawable(mContext, R.drawable.trip_button_stopping_shape));
liveMapButton.setEnabled(false);
} else {
tripButton.setText(R.string.TripButtonTitleStart);
tripButton.setBackground(ContextCompat.getDrawable(mContext, R.drawable.trip_button_start_shape));
liveMapButton.setEnabled(false);
}
}
To debug the issue i verified the following:
Text and background resource is correctly defined (i.e. trying to use
it instead of the first and third case works)
The if-else conditions runs when expected (i.e. the "else if" condition actually runs when I expect it to. Verified by breakpoint.)
No other if-else condition is used in the process. (i.e, only the correct condition is run.)
Some other code that could possibly be relevant:
This is how the Activity requests that the GPS logging should stop (Leading to the processing step before finishing)
private void EndTrip() {
//Create message to TripService with intent to run case for END_TRIP
Message message = Message.obtain(null, TripService.END_TRIP, 0, 0);
//Send the Message to the Service
try {
mMessenger.send(message);
Toast.makeText(mContext, R.string.TripStopToast, Toast.LENGTH_SHORT).show();
} catch (RemoteException e) {
Log.e("Debug", "Failed to contact TripService");
}
}
This is the structure of what happens in the Service after receiving the message from the Activity.
private void EndTrip() {
//Stop retrieving location updates
//Broadcast the updated status and begin processing the trip
mIsTripActive = false;
mIsProcessing = true;
UpdateStatusBroadcast();
//Processing the collected data
//Finish up
mIsProcessing = false;
UpdateStatusBroadcast();
stopForeground(true);
}
I am all out of ideas. What can the cause be? Why does the button background not change in the else-if?

After too many hours of trial and error, I found the cause to be thread-related.
What I learned:
My service doing its work (Processing) would hang up the UI thread until done
This was quite simply because the service was running on the UI thread
Android does not automatically run services in a thread seperate from the rest of your application.
It is possible to run your service on a different thread. To do this, add the following to your AndroidManifest, inside your service:
android:process=":WhateverNameYouLikeForYourThread"
Note that this of course broke the broadcasts i relied on. This was however easy to fix; The consequence is that I can no longer use LocalBroadcastManager
By example - Instead of
LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
i now use
sendBroadcast(intent);
instead. This does however mean that the broadcasts are less private.

What happens to Threads started in Android Service when Android restarts the Service?

I have a Service like this (this is not the actual Service, it's just for describing my problem).
public class UploadService {
private BlockingQueue<UploadData> queue = null;
private UploadInfoReceiver receiver = null;
public void onStart(...) {
queue = new LinkedBlockingQueue<UploadData>();
(new Processor()).start();
// creating and reigtering receiver
}
public void onDestroy() {
queue.add(new ServiceDestroyedData());
// unregistering the receiver
}
private class Processor extends Thread() {
public void run() {
while (true) {
UploadData data = queue.take();
if (data instanceof ServiceDestroyedData) {
return;
}
// processing data
}
}
}
private class UploadInfoReceiver extends BroadcastReceiver {
public void onReceive(Context context, Intent intent) {
queue.add(new UploadData(/* getting data from intent */));
}
}
}
And my problem is that if I do something like this in my App:
if (!isUploadServiceRunning()) {
// start the Service
}
Then it starts the Service, but when I move my App to the background and open task manager (android 4.2.2), and kill the app, Android restart my Service, and I can see that it creates a whole new instance of it, and I can see that onDestroy never gets called for the previous Service instance. And I also can see that the instance of the previous Processor Thread is no longer running. How can this be? If onDestroy never gets called how does Android know that it should stop my Thread?
Thanks for your answers.

Android will kill off anything that it finds that is attached to your apps classloader when you select force stop from the menu. Think kill -9 on Linux. There will be no nice callbacks to any onDestroy methods, the system will just end everything.
Now for your service:
while(true) should really NEVER be used. It will instantly kill the battery and will not do any work 99% of the time anyway.
You area already using a receiver, you can just put your while logic into there and once the upload is done call the next upload and so on. There is absolutely no need for the loop.

get notified when requestSync function completed

im trying to start the calendar sync programatically using this code
Bundle bundle = new Bundle();
bundle.putBoolean(ContentResolver.SYNC_EXTRAS_EXPEDITED, true);
bundle.putBoolean(ContentResolver.SYNC_EXTRAS_FORCE, true);
bundle.putBoolean(ContentResolver.SYNC_EXTRAS_MANUAL, true);
bundle.putBoolean(ContentResolver.SYNC_EXTRAS_IGNORE_SETTINGS, true);
ContentResolver.requestSync(accounts[0], "com.android.calendar", bundle);
i want a way so i can know when sync complete so i can read data from the calendar
i tried doing this
while (ContentResolver.isSyncActive(accounts[0], "com.android.calendar")) {
System.out.println("looping: " + i);
}
readLocalCalendar();
readLocalEvents();
but the system exit the loop before the sync ends and i can still see the sync sign at the status bar, so any help so i can read calendar events after sync completle done ??
thanks

Another option would be to register a broadcast receiver to tell you when the sync is finished like this:
public class UpdateableActivity extends Activity {
public static final String ACTION_FINISHED_SYNC = "your.package.ACTION_FINISHED_SYNC";
private static IntentFilter syncIntentFilter = new IntentFilter(ACTION_FINISHED_SYNC);
private BroadcastReceiver syncBroadcastReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
// update your views
}
};
#Override
protected void onResume() {
super.onResume();
// register for sync
registerReceiver(syncBroadcastReceiver, syncIntentFilter);
// do your resuming magic
}
#Override
protected void onPause() {
unregisterReceiver(syncBroadcastReceiver);
super.onPause();
}
}
Inside your SyncAdapter use this when done:
getContext().sendBroadcast(new Intent(UpdateableActivity.ACTION_FINISHED_SYNC));
You can also use this for when starting or updating the status of the sync ;)
Update: Updated the code to avoid leaks and making sure the activity is still active (onResume/onPause)

using the addStatusChangeListener actually worked for me .
here's a reference .
don't forget to add the needed permissions .

Use ContentResolver.addStatusChangeListener (int mask, SyncStatusObserver callback) to get notified of changes in sync status. docs
Please do not loop forever, its really bad design. Using the above method everything is asynchronous so you don't waste any cpu cycles.
You could also use ContentResolver.registerContentObserver (Uri uri, boolean notifyForDescendents, ContentObserver observer) docs to get notified in changes on a specific URI (like the calendar's URI)

try an AsyncTask :
private class CustomTask extends AsyncTask<Void, Void, Void>{
#Override
protected Void doInBackground(Void... params) {
// TODO sync your calendar
}
protected void onProgressUpdate(Void... progress) {
//TODO display a spinner or something else to show progress
}
protected void onPostExecute(Void t){
//TODO what you want when doInBackground has finished
}
}
Good luck !

Restful API service

I'm looking to make a service which I can use to make calls to a web-based REST API.
Basically I want to start a service on app init then I want to be able to ask that service to request a url and return the results. In the meantime I want to be able to display a progress window or something similar.
I've created a service currently which uses IDL, I've read somewhere that you only really need this for cross app communication, so think these needs stripping out but unsure how to do callbacks without it. Also when I hit the post(Config.getURL("login"), values) the app seems to pause for a while (seems weird - thought the idea behind a service was that it runs on a different thread!)
Currently I have a service with post and get http methods inside, a couple of AIDL files (for two way communication), a ServiceManager which deals with starting, stopping, binding etc to the service and I'm dynamically creating a Handler with specific code for the callbacks as needed.
I don't want anyone to give me a complete code base to work on, but some pointers would be greatly appreciated.
Code in (mostly) full:
public class RestfulAPIService extends Service {
final RemoteCallbackList<IRemoteServiceCallback> mCallbacks = new RemoteCallbackList<IRemoteServiceCallback>();
public void onStart(Intent intent, int startId) {
super.onStart(intent, startId);
}
public IBinder onBind(Intent intent) {
return binder;
}
public void onCreate() {
super.onCreate();
}
public void onDestroy() {
super.onDestroy();
mCallbacks.kill();
}
private final IRestfulService.Stub binder = new IRestfulService.Stub() {
public void doLogin(String username, String password) {
Message msg = new Message();
Bundle data = new Bundle();
HashMap<String, String> values = new HashMap<String, String>();
values.put("username", username);
values.put("password", password);
String result = post(Config.getURL("login"), values);
data.putString("response", result);
msg.setData(data);
msg.what = Config.ACTION_LOGIN;
mHandler.sendMessage(msg);
}
public void registerCallback(IRemoteServiceCallback cb) {
if (cb != null)
mCallbacks.register(cb);
}
};
private final Handler mHandler = new Handler() {
public void handleMessage(Message msg) {
// Broadcast to all clients the new value.
final int N = mCallbacks.beginBroadcast();
for (int i = 0; i < N; i++) {
try {
switch (msg.what) {
case Config.ACTION_LOGIN:
mCallbacks.getBroadcastItem(i).userLogIn( msg.getData().getString("response"));
break;
default:
super.handleMessage(msg);
return;
}
} catch (RemoteException e) {
}
}
mCallbacks.finishBroadcast();
}
public String post(String url, HashMap<String, String> namePairs) {...}
public String get(String url) {...}
};
A couple of AIDL files:
package com.something.android
oneway interface IRemoteServiceCallback {
void userLogIn(String result);
}
and
package com.something.android
import com.something.android.IRemoteServiceCallback;
interface IRestfulService {
void doLogin(in String username, in String password);
void registerCallback(IRemoteServiceCallback cb);
}
and the service manager:
public class ServiceManager {
final RemoteCallbackList<IRemoteServiceCallback> mCallbacks = new RemoteCallbackList<IRemoteServiceCallback>();
public IRestfulService restfulService;
private RestfulServiceConnection conn;
private boolean started = false;
private Context context;
public ServiceManager(Context context) {
this.context = context;
}
public void startService() {
if (started) {
Toast.makeText(context, "Service already started", Toast.LENGTH_SHORT).show();
} else {
Intent i = new Intent();
i.setClassName("com.something.android", "com.something.android.RestfulAPIService");
context.startService(i);
started = true;
}
}
public void stopService() {
if (!started) {
Toast.makeText(context, "Service not yet started", Toast.LENGTH_SHORT).show();
} else {
Intent i = new Intent();
i.setClassName("com.something.android", "com.something.android.RestfulAPIService");
context.stopService(i);
started = false;
}
}
public void bindService() {
if (conn == null) {
conn = new RestfulServiceConnection();
Intent i = new Intent();
i.setClassName("com.something.android", "com.something.android.RestfulAPIService");
context.bindService(i, conn, Context.BIND_AUTO_CREATE);
} else {
Toast.makeText(context, "Cannot bind - service already bound", Toast.LENGTH_SHORT).show();
}
}
protected void destroy() {
releaseService();
}
private void releaseService() {
if (conn != null) {
context.unbindService(conn);
conn = null;
Log.d(LOG_TAG, "unbindService()");
} else {
Toast.makeText(context, "Cannot unbind - service not bound", Toast.LENGTH_SHORT).show();
}
}
class RestfulServiceConnection implements ServiceConnection {
public void onServiceConnected(ComponentName className, IBinder boundService) {
restfulService = IRestfulService.Stub.asInterface((IBinder) boundService);
try {
restfulService.registerCallback(mCallback);
} catch (RemoteException e) {}
}
public void onServiceDisconnected(ComponentName className) {
restfulService = null;
}
};
private IRemoteServiceCallback mCallback = new IRemoteServiceCallback.Stub() {
public void userLogIn(String result) throws RemoteException {
mHandler.sendMessage(mHandler.obtainMessage(Config.ACTION_LOGIN, result));
}
};
private Handler mHandler;
public void setHandler(Handler handler) {
mHandler = handler;
}
}
Service init and bind:
// this I'm calling on app onCreate
servicemanager = new ServiceManager(this);
servicemanager.startService();
servicemanager.bindService();
application = (ApplicationState)this.getApplication();
application.setServiceManager(servicemanager);
service function call:
// this lot i'm calling as required - in this example for login
progressDialog = new ProgressDialog(Login.this);
progressDialog.setMessage("Logging you in...");
progressDialog.show();
application = (ApplicationState) getApplication();
servicemanager = application.getServiceManager();
servicemanager.setHandler(mHandler);
try {
servicemanager.restfulService.doLogin(args[0], args[1]);
} catch (RemoteException e) {
e.printStackTrace();
}
...later in the same file...
Handler mHandler = new Handler() {
public void handleMessage(Message msg) {
switch (msg.what) {
case Config.ACTION_LOGIN:
if (progressDialog.isShowing()) {
progressDialog.dismiss();
}
try {
...process login results...
}
} catch (JSONException e) {
Log.e("JSON", "There was an error parsing the JSON", e);
}
break;
default:
super.handleMessage(msg);
}
}
};

If your service is going to be part of you application then you are making it way more complex than it needs to be. Since you have a simple use case of getting some data from a RESTful Web Service, you should look into ResultReceiver and IntentService.
This Service + ResultReceiver pattern works by starting or binding to the service with startService() when you want to do some action. You can specify the operation to perform and pass in your ResultReceiver (the activity) through the extras in the Intent.
In the service you implement onHandleIntent to do the operation that is specified in the Intent. When the operation is completed you use the passed in ResultReceiver to send a message back to the Activity at which point onReceiveResult will be called.
So for example, you want to pull some data from your Web Service.
You create the intent and call startService.
The operation in the service starts and it sends the activity a message saying it started
The activity processes the message and shows a progress.
The service finishes the operation and sends some data back to your activity.
Your activity processes the data and puts in in a list view
The service sends you a message saying that it is done, and it kills itself.
The activity gets the finish message and hides the progress dialog.
I know you mentioned you didn't want a code base but the open source Google I/O 2010 app uses a service in this way I am describing.
Updated to add sample code:
The activity.
public class HomeActivity extends Activity implements MyResultReceiver.Receiver {
public MyResultReceiver mReceiver;
public void onCreate(Bundle savedInstanceState) {
mReceiver = new MyResultReceiver(new Handler());
mReceiver.setReceiver(this);
...
final Intent intent = new Intent(Intent.ACTION_SYNC, null, this, QueryService.class);
intent.putExtra("receiver", mReceiver);
intent.putExtra("command", "query");
startService(intent);
}
public void onPause() {
mReceiver.setReceiver(null); // clear receiver so no leaks.
}
public void onReceiveResult(int resultCode, Bundle resultData) {
switch (resultCode) {
case RUNNING:
//show progress
break;
case FINISHED:
List results = resultData.getParcelableList("results");
// do something interesting
// hide progress
break;
case ERROR:
// handle the error;
break;
}
}
The Service:
public class QueryService extends IntentService {
protected void onHandleIntent(Intent intent) {
final ResultReceiver receiver = intent.getParcelableExtra("receiver");
String command = intent.getStringExtra("command");
Bundle b = new Bundle();
if(command.equals("query") {
receiver.send(STATUS_RUNNING, Bundle.EMPTY);
try {
// get some data or something
b.putParcelableArrayList("results", results);
receiver.send(STATUS_FINISHED, b)
} catch(Exception e) {
b.putString(Intent.EXTRA_TEXT, e.toString());
receiver.send(STATUS_ERROR, b);
}
}
}
}
ResultReceiver extension - edited about to implement MyResultReceiver.Receiver
public class MyResultReceiver implements ResultReceiver {
private Receiver mReceiver;
public MyResultReceiver(Handler handler) {
super(handler);
}
public void setReceiver(Receiver receiver) {
mReceiver = receiver;
}
public interface Receiver {
public void onReceiveResult(int resultCode, Bundle resultData);
}
#Override
protected void onReceiveResult(int resultCode, Bundle resultData) {
if (mReceiver != null) {
mReceiver.onReceiveResult(resultCode, resultData);
}
}
}

Developing Android REST client applications has been an awesome resource for me. The speaker does not show any code, he just goes over design considerations and techniques in putting together a rock solid Rest Api in android. If your a podcast kinda person or not, I'd recommend giving this one at least one listen but, personally I've listened to it like 4 or five times thus far and I'm probably going to listen to it again.
Developing Android REST client applications
Author: Virgil Dobjanschi
Description:
This session will present architectural considerations for developing RESTful applications on the Android platform. It focuses on design patterns, platform integration and performance issues specific to the Android platform.
And there are so many considerations I really hadn't made in the first version of my api that I've had to refactor

Also when I hit
the post(Config.getURL("login"),
values) the app seems to pause for a
while (seems weird - thought the idea
behind a service was that it runs on a
different thread!)
No you have to create a thread yourself, a Local service runs in the UI thread by default.

I know #Martyn does not want full code, but I think this annotation its good for this question:
10 Open Source Android Apps which every Android developer must look into
Foursquared for Android is open-source, and have an interesting code pattern interacting with the foursquare REST API.

I would highly recommend the REST client Retrofit.
I have found this well written blog post extremely helpful, it also contains simple example code.
The author uses Retrofit to make the network calls and Otto to implement a data bus pattern:
http://www.mdswanson.com/blog/2014/04/07/durable-android-rest-clients.html

Just wanted to point you all in the direction of an standalone class I rolled that incorporates all of the functionality.
http://github.com/StlTenny/RestService
It executes the request as non-blocking, and returns the results in an easy to implement handler. Even comes with an example implementation.

Lets say I want to start the service on an event - onItemClicked() of a button. The Receiver mechanism would not work in that case because :-
a) I passed the Receiver to the service (as in Intent extra) from onItemClicked()
b) Activity moves to the background. In onPause() I set the receiver reference within the ResultReceiver to null to avoid leaking the Activity.
c) Activity gets destroyed.
d) Activity gets created again. However at this point the Service will not be able to make a callback to the Activity as that receiver reference is lost.
The mechanism of a limited broadcast or a PendingIntent seems to be more usefull in such scenarios- refer to Notify activity from service

Note that the solution from Robby Pond is somehow lacking: in this way you only allow todo one api call at a time since the IntentService only handles one intent at a time. Often you want to perform parallel api calls. If you want todo this you have to extend Service instead of IntentService and create your own thread.

Also when I hit the post(Config.getURL("login"), values) the app seems to pause for a while (seems weird - thought the idea behind a service was that it runs on a different thread!)
In this case its better to use asynctask, which runs on a different thread and return result back to the ui thread on completion.

Robby provides a great answer, though I can see you still looking for more information. I implemented REST api calls the easy BUT wrong way. It wasn't until watching this Google I/O video that I understood where I went wrong. It's not as simple as putting together an AsyncTask with a HttpUrlConnection get/put call.

There is another approach here which basically helps you to forget about the whole management of the requests. It is based on an async queue method and a callable/callback based response.
The main advantage is that by using this method you'll be able to make the whole process (request, get and parse response, sabe to db) completely transparent for you. Once you get the response code the work is already done. After that you just need to make a call to your db and you are done.
It helps as well with the problematic of what happens when your activity is not active.
What will happen here is that you'll have all your data saved in your local database but the response won't be processed by your activity, that's the ideal way.