Restful API service

Question

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 lt IRemoteServiceCallback gt  mCallbacks   new RemoteCallbackList lt IRemoteServiceCallback gt      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 lt String  String gt  values   new HashMap lt String  String gt             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  lt  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 lt String  String gt  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 lt IRemoteServiceCallback gt  mCallbacks   new RemoteCallbackList lt IRemoteServiceCallback gt         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

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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

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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   I wrote about a general approach here  http   ugiagonzalez com 2012 07 02 theres-life-after-asynctasks-in-android   I ll be putting specific sample code in upcoming posts  Hope it helps  feel free to contact me for sharing the approach and solving potential doubts or issues

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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

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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

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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

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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

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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

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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

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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

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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

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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

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