What is the cleanest way to create a GUIless application?

Good Morning.

I have a question about how to create an application without GUI. It should start when the user pushes the icon. Reading other posts, seems that the natural way of doing this would be a Service.

Since the app has no GUI, it makes no sense to add any Activity. For this reason, the Service has to be unbinded. So, if there is no component calling startService, and no external component is sending an intent, ¿how does the service start?

Is there any attribute in the manifest to achieve this? Or maybe extending Application and using onCreate to start the service?

Thanks.

UPDATES: -There's no way to start a Service in the sam开发者_JAVA百科e app without an Intent. Other options would be autostart or Broadcast receivers, but these don't fit my requirements. -Tried a test app without Activities, and the icon isn't even showing in the launcher. Don't know the reason of this, maybe related to the manifest not having a LAUNCHER activity.

The list of applications shown in the Android launcher is basically the list of all activities in the system that have a LAUNCHER intent filter:

<intent-filter>
    <action android:name="android.intent.action.MAIN" />
    <category android:name="android.intent.category.LAUNCHER" />
</intent-filter>

If you put this intent filter on a <service>, it will not work (just tried). Thus, the only way to do what you want to do is through an Activity. I think the cleanest way is something like this:

public void onCreate(Bundle savedInstanceState) {
    Intent service = new Intent(this, MyService.class);
    startService(service);
    Toast.makeText(this, "Service started.", Toast.LENGTH_SHORT).show();
    finish();
}

The user will not see anything except a small message at the bottom of the screen saying "Service started." that will automatically disappear in a couple of seconds. It's clean and user-friendly.

The service is started either when somebody calls startService() or when somebody calls bindService(). Note that if service is only started via bindService() it will be automatically stopped when Activity either explicitly unbinds from it or is destroyed (and it was the only binder).

You can declare BOOT_COMPLETED_ACTION broadcast receiver in your AndroidManifest.xml and start your service on system boot. But you service will only start on next device reboot. And there are some issues with applications without activities and this broadcast event in Android 3.1. More info can be found here.

In general, its good to have at least one activity in your application, even if your primary component is service. This activity will start the service when user launches it, and also may expose some ability to configure the service behavior.

Example of activity that starts service:

public class ServiceStarterActivity extends Activity
{       
    @Override
    public void onCreate(Bundle savedInstanceState) 
    {       
        super.onCreate(savedInstanceState);       

        startService(new Intent(this, ServiceA.class));
        finish();
    }    
}