Question

I’m trying to implement a service to handle the communication with the server for the following code. I don’t know much about the design architecture for these.

Here is my service class

public class BgService extends Service {
    private static final String TAG = BgService.class.getSimpleName();
    private Timer timer;
    SendJsonRequest sjr;

    private TimerTask updateTask = new TimerTask(){
        @Override
        public void run(){
            try{
                SendJsonRequest sjr = new SendJsonRequest();
                sjr.carMake();
                Log.i(TAG, "LOOK AT ME");
            }
            catch(Exception e){
                Log.w(TAG,e);
            }
        }
    };
    @Override
    public IBinder onBind(Intent intent) {
        // TODO Auto-generated method stub
        return null;
    }
    @Override
    public void onCreate(){
        super.onCreate();
        Log.i(TAG, "Service creating");
        timer = new Timer("Server listening timer");
        timer.schedule(updateTask, 1000L, 60*1000L);
    }

    @Override
    public void onDestroy(){
        super.onDestroy();
        Log.i(TAG, "Service Destroying");
        timer.cancel();
        timer = null;
    }
}

Here is my SendJsonRequest class

public class SendJsonRequest{
         private static final String TAG = "SendJsonRequest";
         private static String URL = "xxxxxxxxx";
         private static String infoRec;

         public static void createJsonObj(String path, Map x){
             infoRec = CreateJsonRequest.jsonRequest(URL+path, x );
             System.out.println(infoRec);
         }
         public static void carMake(){
             String path = "/CarMake";
             Map<String, Object> z = new HashMap<String,Object>();
             z.put("Name", "Ford");
             z.put("Model", "Mustang");
             createJsonObj(path, z);
         }

        }

Here is my CreateJsonObject class

public class CreateJsonRequest {
    public static String jsonRequest(String URL, Map<String,Object> params){
        try{
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(URL);

            JSONObject holder = new JSONObject();

            for (Map.Entry<String, Object> m : params.entrySet()){
                try {
                    holder.put(m.getKey(), m.getValue());
                }
                catch (JSONException e) {
                    Log.e("Hmmmm", "JSONException : "+e);
                }
            }   
            StringEntity se;
            se = new StringEntity(holder.toString());

            httpPost.setEntity(se);
            httpPost.setHeader("Accept", "text/json");
            httpPost.setHeader("Content-type", "text/json");

            HttpResponse response = (HttpResponse) httpClient.execute(httpPost);
            HttpEntity entity = response.getEntity();

            if(entity != null){
                InputStream is = entity.getContent();
                Header contentEncoding = response.getFirstHeader("Content-Encoding");

                String result= convertToString(is);
                is.close();

                System.out.println(result);
                return result;

            }
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
        return null;
    }

Sorry for the massive amount of code. How I implemented my service is obviously not correct, I just have no clue where to start to get a service handling the json requests to the server. Thanks in advance.

To be more clear, this did work on a button click, now I’m trying to get it to all run in the background with the service. So I guess my question is what goes where in the service?

My activity successfully starts the service, the service would work and print “look at me” to the logcat every minute. Then I added the try{ sjr.carMake()} and it catches an exception.

Answer 1

You can use a broadcast receiver. This is a way to have your code start at certain times indicated by Android OS – for example, you can have it start when Android finished booting up (this is where I run my services usually.

The best way is to use the AlarmManager class, and tell your service how often to run.

Tell us more about what you’re trying to do, and what the problem is, and we can give you a more concise answer…

UPDATE:

Have you created an entry in the manifest.xml file for the service?

UPDATE
Here is how I’m doing it in my application. This is your “hook” to the OS. It’s going to fire when it finishes booting (don’t forget to make in entry in the manifest for this!)

public class TmBroadcastReceiver extends BroadcastReceiver {
 @Override
     public void onReceive(final Context context, final Intent bootintent) {

         try{
             Log.i("Taskmotion-ROBOT", "Robot Broadcast signal received on Boot. Trying to start Alarm scheduler");
              Intent mServiceIntent = new Intent(context, ServiceAlarm.class);
              context.startService(mServiceIntent);

         }
         catch(Exception e)
         {
            Log.i("Taskmotion", "Failed to start service..."); 

         }
     }
}

This Broadcast receiver calls a service that implements the AlarmManager class. The alarm manager sets up a schedule to run my service at a specified interval. Note that the alarms are deleted when the phone is shut down – but then recreated again when process is repeated as the phone boots back up and runs the BroadcastReceiver again.

public class ServiceAlarm extends Service {
 private PendingIntent mAlarmSender;


 @Override
 public void onCreate() {

     try{
         Log.i("Taskmotion-ROBOT", "Setting Service Alarm Step 1");
         mAlarmSender = PendingIntent.getService(this.getApplicationContext(),
                 0, new Intent(this.getApplicationContext(), BackgroundService.class), 0);
     }
     catch(Exception e)
     {
         Log.i("Taskmotion-ROBOT", "Problem at 1 :" + e.toString());

     }

     long firstTime = SystemClock.elapsedRealtime();

     Log.i("Taskmotion-ROBOT", "Setting Service Alarm Step 2");
     // Schedule the alarm!
     AlarmManager am = (AlarmManager)getSystemService(ALARM_SERVICE);
     am.setRepeating(AlarmManager.ELAPSED_REALTIME,
                     firstTime, AlarmManager.INTERVAL_HOUR, mAlarmSender);

     this.stopSelf();


 }



@Override
public IBinder onBind(Intent arg0) {
    // TODO Auto-generated method stub
    return null;
}


}

I haven’t refactored this code yet, it was my first go at it. I see now that I’m looking at it again that I could probably do the scheduling inside the BroadcastReceiver, but for the sake of getting you something that works, I’ll continue.

As indicated by AlarmManager.INTERVAL_HOUR, my service will run once an hour. The service that I want to run is defined in the pendingIntent (BackgroundService.class). This is where you put your own service class.
I reworked your service class for you, and removed the timer (functionality replaced by the BroadcastReceiver & AlarmManager).

public class BgService extends Service {
    private static final String TAG = BgService.class.getSimpleName();
    SendJsonRequest sjr;


    @Override
    public IBinder onBind(Intent intent) {
        // TODO Auto-generated method stub
        return null;
    }
    @Override
    public void onCreate(){
        super.onCreate();
        Log.i(TAG, "Service creating");


//DO YOUR WORK WITH YOUR JSON CLASS HERE
//**************************************

//Make sure to call stopSelf() or your service will run in the background, chewing up
//battery life like rocky mountain oysters!
this.stopSelf();


    }

    @Override
    public void onDestroy(){
        super.onDestroy();
    }
}