отправлять данные на сервер в фоновом режиме каждые x секунд или минут

Сначала добавьте это в mainactivity:

AlarmManager alarmManager;
PendingIntent pendingIntent;
Calendar calendar;
Intent alarm;
final int SDK_INT = Build.VERSION.SDK_INT;

    calendar = Calendar.getInstance();
    calendar.setTimeInMillis(System.currentTimeMillis());

alarmManager = (AlarmManager)getSystemService(Context.ALARM_SERVICE);
alarm = new Intent(this, TestForecastService.class);
pendingIntent = PendingIntent.getService(this, 0, alarm, 0);

if (SDK_INT < Build.VERSION_CODES.KITKAT) {
    alarmManager.set(AlarmManager.RTC_WAKEUP,System.currentTimeMillis()+10000, pendingIntent);
    Log.d("lowerMF","hahah");
}
else if (Build.VERSION_CODES.KITKAT <= SDK_INT  && SDK_INT < Build.VERSION_CODES.M) {
    alarmManager.setExact(AlarmManager.RTC_WAKEUP,System.currentTimeMillis()+10000,pendingIntent);
    Log.d("kitkatMF","hahah");
}
else if (SDK_INT >= Build.VERSION_CODES.M) {
    alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP,System.currentTimeMillis()+10000,pendingIntent);
    Log.d("marshmallowMF","hahah");
}

Теперь TestForecastService: в котором вы можете определить свою работу:

public class TestForecastService extends IntentService {

    Context context;
    PowerManager powerManager;
    PowerManager.WakeLock wakeLock;
    final int SDK_INT = Build.VERSION.SDK_INT;
    AlarmManager alarmManager;
    PendingIntent pendingIntent;
    Intent alarm;

    public TestForecastService() {
        super("");
    }

    @Override
    protected void onHandleIntent(Intent intent) {
        powerManager = (PowerManager) getSystemService(POWER_SERVICE);
        wakeLock = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "FCFCFCFC");

        wakeLock.acquire();
        sendDATA(city);

    }

    private void sendDATA(String city) {
        try {

           ......DO YOUR DATA SENDING WORK.........

        } catch (Exception e) {
            Log.v("fserviceerror","erre");
        }

        reSETALARAM();
        wakeLock.release();
    }

    private void reSETALARAM() {
        alarmManager = (AlarmManager)getSystemService(Context.ALARM_SERVICE);
        alarm = new Intent(this,TestForecastService.class);
        pendingIntent = PendingIntent.getService(this, 0, alarm, 0);

        if (SDK_INT < Build.VERSION_CODES.KITKAT) {
            alarmManager.set(AlarmManager.RTC_WAKEUP,System.currentTimeMillis()+10000, pendingIntent);
            Log.d("lowerFS","hahah");
        }
        else if (Build.VERSION_CODES.KITKAT <= SDK_INT  && SDK_INT < Build.VERSION_CODES.M) {
            alarmManager.setExact(AlarmManager.RTC_WAKEUP,System.currentTimeMillis()+10000,pendingIntent);
            Log.d("kitkatFS","hahah");
        }
        else if (SDK_INT >= Build.VERSION_CODES.M) {
            alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP,System.currentTimeMillis()+10000,pendingIntent);
            Log.d("marshmallowFS","hahah");
        }
    }

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

Теперь создайте класс BrodcastReceiver, который запускает вашу службу при перезапуске устройства:

public class Auto extends BroadcastReceiver {

        final int SDK_INT = Build.VERSION.SDK_INT;

        @Override
        public void onReceive(Context ctx, Intent intent) {

                if (intent.getAction().equals("android.intent.action.BOOT_COMPLETED")){
                        AlarmManager alarmMgr = (AlarmManager) ctx.getSystemService(Context.ALARM_SERVICE);
                        Intent intent1 = new Intent(ctx, TestForecastService.class);
                        PendingIntent alarmIntent = PendingIntent.getService(ctx, 0, intent1, 0);

                        if (SDK_INT < Build.VERSION_CODES.KITKAT) {
                                alarmMgr.set(AlarmManager.RTC_WAKEUP,System.currentTimeMillis()+10000, alarmIntent);
                                Log.d("lowerFB","hahah");
                        }
                        else if (Build.VERSION_CODES.KITKAT <= SDK_INT  && SDK_INT < Build.VERSION_CODES.M) {
                                alarmMgr.setExact(AlarmManager.RTC_WAKEUP,System.currentTimeMillis()+10000,alarmIntent);
                                Log.d("kitkatFB","hahah");
                        }
                        else if (SDK_INT >= Build.VERSION_CODES.M) {
                                alarmMgr.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP,System.currentTimeMillis()+10000,alarmIntent);
                                Log.d("marshmallowFB","hahah");
                        }
                }
        }
    }

Наконец, добавьте это в файл манифеста:

    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
    <uses-permission android:name="com.android.alarm.permission.SET_ALARM"/>
    <uses-permission android:name="android.permission.WAKE_LOCK"/>

<service android:name=".TestForecastService" android:exported="true" android:enabled="true"/>
<receiver android:name=".Auto" android:exported="true" android:enabled="true" >
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED" />
            </intent-filter>
        </receiver>