How can I restart a service in android programatically?

Question

In Android I have an application with different activities and a service. The activities are for direct user interaction, in which the user can change data, update data, entry data, whatever.

The application also has a (background) service running, using the data the user has entered (stock data). The service regulary checks the stock prices (e.g. every 12 hours) and gives the user a notification, if some conditions match.

However, as an user I want to be able to change settings of this service. I start the application, and can enter an update interval in one of the application's activity which is stored in a SharedPreference. I am able to change the value, for example, to have the service check the stock data every 3 hours instead.

Do I then have to 'restart' the service? As I understand 'services' in an operating system, the service runs until stopped by some event. But if the service is not stopped, the service does not 'notice' that the update interval has changed! So, in my activity from my main application I need some way to 'restart' the service, so it checks the stock prices in 3 hours, and not in 12 hours!

Any idea how to accomplish this? A google search did not really help. Maybe I looked for the wrong keywords...?

Answer 1

The standard way to make activities communicate with a service is through an interface using AIDL. In AIDL you define calls to the service, and callbacks from the service. With that, the service behaves like just another class that you can call methods of. There's documentation here.

Answer 2

A simple solution to this since your service runs in the same process as your application would be to register an OnSharedPreferenceChangeListener in your service's onCreate method to the same SharedPreferences that the activity is updating.

Then every time a preference changes onSharedPreferenceChanged(...) will be called in your service. You can check when the update interval preference in particular changes and update your service accordingly without ever having to restart it.

Answer 3

You can send to your service data and actions with Intents. Simply inside your Service class create a BroadcastReceiver and register it with the service life cycle. Now you can update the values from the service. An example:

Your Service

public class CustomService extends Service {

    private BroadcastReceiver mReceiver;

    @Override
    public void onCreate() {
        mReceiver = new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
              // get the action from the intent
            }
        }
        registerReceiver(wifiChangedState, new IntentFilter("CUSTOM");
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        return START_NOT_STICKY;
    }

    @Override
    public void onDestroy() {
        unregisterReceiver(mReceiver);
    }

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

Now you can create your custom Intent to send actions from an Activity that the BroadcastReceiver can receive and apply.

Answer 4

You can create a Service with a custom Binder

    public class CustomService extends Service {

        public IBinder onBind(Intent intent) {
            return new CustomBinder(this);
        }

        public void doSomething(){
            //Do somthing with service
        }

    }

    public class CustomBinder extends Binder {

        private CustomService mCustomService;

        public MyBinder(CustomService service) {
            mCustomService = service;
        }

        public CustomService getCustomService() {
            return mCustomService;
        }
    }

At this point you can bind to CustomService through ServiceConnection (I cannot link ServiceConnection because of my reputation...) implements all functions you need in service.

    Intent customServiceIntent = new Intent(context, CustomService.class);
    context.bindService(
            customServiceIntent, 
            mServiceConnection, 
            Context.BIND_AUTO_CREATE | Context.BIND_NOT_FOREGROUND
    );

    private ServiceConnection mServiceConnection = new ServiceConnection() {
        public void onServiceConnected(ComponentName name, IBinder service) {
            CustomBinder binder = (CustomBinder) service;
            binder.getCustomService().doSomething();
        }
        public void onServiceDisconnected(ComponentName name) {
            /* Do something when service disconnect */
        }
    };

This method is not applicable with services over processes. (multiples applications) take a look at AIDL files to achieve that.

To make sure "work" was execute in time you can use AlarmManager to start your service.

    /* define when intent will be send */
    long wakeUpTimeInMillis = Calendar.getInstance().getTimeInMillis() + 1000 * 30 ; // now + 30second 

    AlarmManager alarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
    Intent intent = new Intent(context, CustomService.class);
    PendingIntent pending = PendingIntent.getBroadcast(context, 0, intent, PendingIntent.FLAG_NO_CREATE);
    alarmManager.set(AlarmManager.RTC_WAKEUP, wakeUpTimeInMillis, pending);

You can add some additionnal parametters to intent and catch it by overriding onStartCommand(Intent intent, int flags, int startId) in CustomService