Purpose of Service Intent-Filter inside Manifest.xml

Question

from android developers : \"Components(service) advertise their capabilities — the kinds of intents they can respond to — through intent filters.

I just cant underst

Answer 1

If you want to use a service to perform different actions, then declaring an intent filter will help your service match against different actions you want to perform.

The example will explain better.
Suppose you have following declaration in manifest file:

<service
    android:name="MyService" >
    <intent-filter>
        <action android:name="com.x.y.DOWNLOAD_DATA" />
        <action android:name="com.x.y.UPLOAD_DATA" />
    </intent-filter>
</service>

Then in your IntentService you could filter for these actions like this:

public class MyService extends IntentService {

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

    @Override
    protected void onHandleIntent(Intent intent) {
        if(intent.getAction().equals("com.x.y.DOWNLOAD_DATA"){
            //download data here
        }else if(intent.getAction().equals("com.x.y.UPLOAD_DATA"){
            // upload data here
        }
    }
}

Basically, it allows you to use the same service for different actions, instead of creating two separate services for example.

However, having intent filters declared for a service is not regarded as a good practice, and this is what the docs had to say:

Caution: To ensure your app is secure, always use an explicit intent when starting a Service and do not declare intent filters for your services. Using an implicit intent to start a service is a security hazard because you cannot be certain what service will respond to the intent, and the user cannot see which service starts.

Answer 2

You can use intent filters for explicitly calling your service or get your service to be implicitly called where components from any application installed on the user's device can potentially start your service

If you plan on using your service only locally (other applications do not use it), then you don't need to (and should not) supply any intent filters

It is clearly specified in the documentation Declaring a service in the manifest