Local Services

Local services vs. Remote Services

• Local services are used by components in the same process (or VM?)

• Remote services are accessible to other processes.

– The interface for remote services is more complicated than for local services

• Examples

– Audio player

• The GUI is an activity

• The player is a local service that keeps on running although the GUI is no longer running (e.g., the GUI is not in focus or was closed)

– Map tracker: something that marks your path on a map

• The gui is an activity

• Recording the locations is in a local service, so that the path is kept p to date even though the activity is no longer running

– Fancy location provider: something that is better than the GPS based location provider built into the android

• This should be a remote service so that different applications can use it. If it was a local service, then each app would have to have its own copy

Local service (video)

• There are two parts, the service and the activity that uses the service

• Start a new project called FunWithLocalServices as usual

• Add a new class MyService, but derive it from android.app.Service

MyService

Add:

@Override

public void onCreate() {

super.onCreate();

Log.d("MyService","Created");

}

Add:

@Override

public void onDestroy() {

super.onDestroy();

Log.d("MyService","Destroyed");

}

In manifest, add <service android:name=".MyService"></service>

FunWithLocalServices

In onCreate add:

Log.d(“FunWithLocalServices","Starting Service");

startService(new Intent(this, MyService.class));

MyService (video)

Add:

int val = 0; // this could be anything, a function whatever

We want to provide access to MyServices member variables and functions. A binder will do this:

private final Binder binder = new LocalBinder();

public class LocalBinder extends Binder {

MyService getService() {

Log.d("MyService","localbinder");

return MyService.this;

}

}

Make onBind() return binder

Save

FunWithLocalServices

Add variable:

private MyService myService = null;

And

private ServiceConnection connectionToMyService = new ServiceConnection() {

@Override

public void onServiceConnected(ComponentName className, IBinder rawBinder) {

myService = ((MyService.LocalBinder)rawBinder).getService();

}

@Override

public void onServiceDisconnected(ComponentName name) {

myService = null;

}

};

In onCreate add:

bindService(new Intent(this, MyService.class), connectionToMyService, BIND_AUTO_CREATE);

At the end of onDestroy add:

unbindService(connectionToMyService);

FunWithLocalServices continued

The myService variable provides access to MyServices. Let’s use it

Add button and button listener:

Button button = (Button)findViewById(R.id.Button01);

button.setOnClickListener(new View.OnClickListener() {

public void onClick(View v) {

Log.d("MyLocalSERVICE","val="+myService.cnt); }

});

Note: we cannot get access to myService in onCreate (which is where Bind is called). So we use the button press.