Periodically Update Data from Server in Background

Update data from server at regular time intervals in background process using AlarmManager, BroadcastReceiver, Service and Notification Manager.

First Activate AlarmManager. Write below code in Activity class

public class MainActivity extends ListActivity {
 
  private static final long REPEAT_TIME = 1000 * 30;
 
        @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); setRecurringAlarm(this); }
        
        private void setRecurringAlarm(Context context) {

            Calendar updateTime = Calendar.getInstance();
            updateTime.setTimeZone(TimeZone.getDefault());
            updateTime.set(Calendar.HOUR_OF_DAY, 12);
            updateTime.set(Calendar.MINUTE, 30);
            Intent downloader = new Intent(context, MyStartServiceReceiver.class);
            downloader.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

            PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0, downloader,       PendingIntent.FLAG_CANCEL_CURRENT);

            AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);

            alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, updateTime.getTimeInMillis(), AlarmManager.INTERVAL_FIFTEEN_MINUTES, pendingIntent);
            
            Log.d("MyActivity", "Set alarmManager.setRepeating to: " + updateTime.getTime().toLocaleString());
       
      }

}


First create BroadcastReceiver Class

public class MyStartServiceReceiver extends BroadcastReceiver { 

     @Override
     public void onReceive(Context context, Intent intent) {
            Intent dailyUpdater = new Intent(context, MyService.class); 

            context.startService(dailyUpdater);

            Log.d("AlarmReceiver", "Called context.startService from AlarmReceiver.onReceive");
    } 

}

When application is closed or is in background, periodically fetch data from server and show notification on status bar.

Create Service

public class MyService extends IntentService {

    public MyService() {

       super("MyServiceName");

    }

    @Override

    protected void onHandleIntent(Intent intent) {

        Log.d("MyService", "About to execute MyTask");

        new MyTask().execute();

        this.sendNotification(this);

    }

    private class MyTask extends AsyncTask<String, Void, Boolean> {

        @Override 

         protected Boolean doInBackground(String... strings) {

                Log.d("MyService - MyTask", "Calling doInBackground within MyTask");

               return false;

        } 

 }        

private void sendNotification(Context context) {

        Intent notificationIntent = new Intent(context, MainActivity.class);

        PendingIntent contentIntent = PendingIntent.getActivity(context, 0, notificationIntent, 0);

        NotificationManager notificationMgr = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);

        Notification notification =  new Notification(android.R.drawable.star_on, "Refresh", System.currentTimeMillis());

        notification.flags |= Notification.FLAG_AUTO_CANCEL;

        notification.setLatestEventInfo(context, "Title","Content", contentIntent);

        notificationMgr.notify(0, notification);

     }

}

Don't forget write below lines in AndroidManifest.xml File 

<service android:name="MyService" ></service> 

<receiver android:name="MyStartServiceReceiver" ></receiver>

Fetching Data from Server And Setting Custom Spinner

Create Country model with required fields and set getter and setter properties.

public class Country {

private String countryCode;
private String countryName; 

public String getCountryCode() {
      return countryCode;
}
public void setCountryCode(String string) {
      this.countryCode = string;
}
public String getCountryName() {
      return countryName;
}
public void setCountryName(String countryName) {
      this.countryName = countryName;
}

          }

Fetching Country Details from Server

First create class that deal with webserver, do URL connection and get JSON response, then parse JSON response using JSON object and save it in arrayList  of Country class.

public class WSCountry {

     Context mContext;

      WebServiceUtil webserviceutil;

public WSCountry(Context context) {

mContext = context;

              }

public ArrayList<Country> CountryCode() {
ArrayList<Country> arrCountries = new ArrayList<Country>();

String parsedString = "";
try {
URL url = new URL("your url");

URLConnection conn = url.openConnection();

                             HttpURLConnection httpConn = (HttpURLConnection) conn;  

                                httpConn.setAllowUserInteraction(false);  

                                httpConn.setInstanceFollowRedirects(true); httpConn.setRequestMethod("GET"); httpConn.connect();

InputStream is = httpConn.getInputStream();

parsedString = convertinputStreamToString(is);

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

arrCountries = ParseJson(parsedString); 
return arrCountries; }

public static ArrayList<Country> ParseJson(String jsonstring) {
ArrayList<Country> arrCountries = new ArrayList<Country>();
String status;

String message = "";

                      try {
JSONObject json = new JSONObject(jsonstring); 
status = json.getString("result"); if (status.equalsIgnoreCase("success")) {

                         // [{"countryCode":"00","countryName":"World Wide"},                                               {"countryCode":"kr","countryName":"Korea, Republic of"},{"countryCode":"us","countryName":"United States"}]

JSONArray nameArray = json.names();

JSONArray valArray = json.toJSONArray(nameArray);

                      JSONArray valArray1 = valArray.getJSONArray(1);

valArray1.toString().replace("[", "");

valArray1.toString().replace("]", "");

int len = valArray1.length();

for (int i = 0; i < valArray1.length(); i++) {
Country country = new Country();

JSONObject arr = valArray1.getJSONObject(i);
country.setCountryCode(arr.getString("countryCode"));

country.setCountryName(arr.getString("countryName"));

                     arrCountries.add(country);

}

                }

} catch (JSONException e) {

                               Log.e("JSON", "There was an error parsing the JSON", e); 
}
return arrCountries;
}

public static String convertinputStreamToString(InputStream ists) throws IOException {         

       if (ists != null) {

               StringBuilder sb = new StringBuilder();
               String line;
               try {
                     BufferedReader r1 = new BufferedReader(new InputStreamReader( ists, "UTF-8")); 

                     while ((line = r1.readLine()) != null) 

                                sb.append(line).append("\n");

                } finally {
                        ists.close();
                }
                return sb.toString();
      } else {
                return "";
      }
} 

}

Create Custom Spinner Adapter class.

private class MyAdapter implements SpinnerAdapter {  

          ArrayList<Country> data;

public MyAdapter(ArrayList<Country> data) {  

this.data = data;   

}

@Override

public int getCount() { return data.size(); }

@Override

public Object getItem(int position) { return data.get(position); }

@Override

public long getItemId(int position) { return position; }

@Override

public int getItemViewType(int position) {

        return android.R.layout.simple_spinner_dropdown_item;

} 

@Override  

public View getView(int position, View convertView, ViewGroup parent) {  

TextView v = new TextView(getApplicationContext()); v.setTextColor(Color.BLACK); v.setText(data.get(position).getCountryName()); return v;  

}  

@Override  

public int getViewTypeCount() { return 1; }  

@Override  

public boolean hasStableIds() { return false; }  

@Override  

public boolean isEmpty() { return false; }  

@Override  

public void registerDataSetObserver(DataSetObserver observer) {  

// TODO Auto-generated method stub  

}

@Override  

public void unregisterDataSetObserver(DataSetObserver observer) {  

// TODO Auto-generated method stub  

} 

@Override  

public View getDropDownView(int position, View convertView, ViewGroup parent) {  

return this.getView(position, convertView, parent);  

} }

Create AsyncTask to fetch country details in background and Setting the Spinner adapter in postExecute class.

private class CountryService extends AsyncTask<Void, Void, Void> { 

@Override  

protected void onPreExecute() {  

      super.onPreExecute();  

      try {

         progressDialog = ProgressDialog.show(SignUpActivity.this, "", "Fetching       Countries", true, false);  

       } catch (Exception e) {  

            e.printStackTrace();  

} 

}

@Override   

protected Void doInBackground(Void... params) { 

try {  

       arrayCountries = objwscountry.CountryCode();  

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

 return null;  

}

@Override  

protected void onPostExecute(Void result) {  

super.onPostExecute(result);
progressDialog.dismiss(); 

MyAdapter adapter = new MyAdapter(arrayCountries); spinCountry.setAdapter(adapter);  

spinCountry.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {   

public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {  

       Country country = (Country) parent.getItemAtPosition(pos);  

       countryCode = country.getCountryCode();  

} 

public void onNothingSelected(AdapterView parent) { // Do nothing. }  

});  

} }