What is the advantage of binding to a Service to get its variables, as opposed to using SharedPrefs, or getting the variables directly?

Question

I've got a service meant to sometimes run in the background - started with startService(). What is the advantage of binding to this service so as to get/set its variables, instead of - controversial, I know, but still - just accessing its public variables directly (e.g. myVar = mainService.itsVar), or using SharedPrefs to set and get the values? Especially, what is the fastest, in terms of performance, based on the fact that the get interval would be roughly 3 seconds?

kfir · Accepted Answer · 2021-09-14T07:16:10.787

Advantage - You can access variables and run methods directly. Disadvantage - allot of cross thread headache, not to mention unresolved crashes on google developer console.

How to do it correctly, I will give example of a foreground service, if it can be background then change only how to start it:

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    mContext.startForegroundService(startIntent)
 } else {
    mContext.startService(startIntent);
 }

In the service you need to implement all binding methods:

private IBinder mBinder = new MyBinder();

public MainService() {
}

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

@Override
public void onRebind(Intent intent) {
    super.onRebind(intent);
}

@Override
public boolean onUnbind(Intent intent) {
    return true;
}

public class MyBinder extends Binder {
    public MainService getService() {
        return com.xxx.xxx.MainService.this;
    }
}

In the activity you need to listen to connection:

private ServiceConnection mServiceConnection = new ServiceConnection() {

    @Override
    public void onServiceDisconnected(ComponentName name) {
        mBoundService = null;

    }

    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
        Log.d(TAG, "connecting");
        MainService.MyBinder myBinder = (MainService.MyBinder) service;
        mBoundService = myBinder.getService();
        mShouldUnbind.set(true);
    }
};

If other activity or alarm can start your service you will need to check every second or so if the service was started by other and bind to it. Important - service run on the same thread like the main/GUI thread - so if you have time consumption actions like camera or uploading - you will need to start a background thread. back communication can be made by calling the GUI/main thread. on foreground service like mine - you need also to manage notifications otherwise the o.s. will kill the service after 5 seconds.

Code example:

if (mShouldUnbind.get() && mBoundService != null)
            val = mBoundService.getTimestamp();

Edit I: advantage: I have a camera foreground service - I can set zoom values directly from the GUI thread since I have a handle to the service. the camera is running on the background thread in the service, but, since the preview is being drawn 30 times pro seconds - the zoom is set without any lag. you will never manage to do it in any other way.

thanks Kfir, and hello again! +1 but I am letting the question unanswered as I am after a deeper explanation of advantages vs. drawbacks from a variables perspective between the 3 options (e.g. what's the point of accessing the variables "directly"?). — Razvan_TK9692, Sep 13 '21 at 21:11
hello again, since you helped me so much - wanted to give share back some knowledge. and I saw you have this old question waiting for answers. no stress about approving the answer. just wanted to share back from my experience. I will anyhow add some more info to the answer — kfir, Sep 14 '21 at 07:08
I find it's a great example of the relevance of binding to a service to SET its variables; more generally, I realise it has to do with threading optimisation, by the looks of it. I was originally interested in the differences involved for the purpose of GETTING variables - I'll look into it a bit more and see whether threading optimisation done in this way could apply to my own use cases. At the time I did bind to the service, and got the variables the right way, but always felt it was a bit over the top. apparently not. thanks — Razvan_TK9692, Sep 16 '21 at 19:09

score 0 · Answer 2 · answered Mar 17 '20 at 11:53

0

there is a difference between bounded service and Unbound service, bounded services are bounded to an activity which binds it and will work only till bounded activity is alive. while a unbounded service will work till the completion even after activity is destroyed, see the below link

Can anybody explain what is difference between unbound and bound service in android

answered Mar 17 '20 at 11:53

Fahad Alotaibi

416
3
9

thanks Fahad. I have edited my question, to mention that I have an unbound service to begin with (started with startService()). I would like to know the fastest way to get the variables of that service, from an activity: binding to it, or via SharedPrefs, or accessing public variables directly. Basically, what is the use of binding to an unbound service? – Razvan_TK9692 Mar 18 '20 at 15:25

What is the advantage of binding to a Service to get its variables, as opposed to using SharedPrefs, or getting the variables directly?

2 Answers2