Develop Reference

Memory leak - Service + thread

I would like to know if I am doing the right thing. I am clearly getting memory leaks, but I can not pin down where - I have submitted a simplified version of where I think the problem lies . . . is there a potential for leak in the following code?
public class MainActivity extends Activity {
filterService mServer;
private void startService() {
Intent mIntent = new Intent(getApplicationContext(), filterService.class);
startService(mIntent);
bindService(mIntent, mConnection, BIND_AUTO_CREATE);
}
private void stopService() {
stopService(new Intent(getApplicationContext(), filterService.class));
unbindService(mConnection);
mConnection = null;
}
ServiceConnection mConnection = new ServiceConnection() {
public void onServiceDisconnected(ComponentName name) {
mServer = null;
}
public void onServiceConnected(ComponentName name, IBinder service) {
LocalBinder mLocalBinder = (LocalBinder)service;
mServer = mLocalBinder.getServerInstance();
}
};
public void onDestroy() {
super.onDestroy();
stopService();
}
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
startService();
}
}
Any comments would be most valuable - thank you.

Better unbind from your service in 'onStop()', because 'onDestroy()' may not be called.
If you use 'startService()' to make your service do whatever it is supposed to do and return with 'START_STICKY' from the 'onStartCommand()' method of the service, then it will not be destroyed.
See the documentation about bound services (The Basics):
When the last client unbinds from the service, the system destroys the service (unless the service was also started by startService()).
This way, you can keep your service alive even though the activity is stopped/ destroyed. As soon as it is finished, it can call 'stopSelf()'.
Another source for memory leaks could be a Handler used for communication with the bound service, but I can't judge that from your code.

bindService() gives NullPointerException and onServiceConnected() never called

Let me start by saying I've been searching for a long time, found a lot of similar questions (on SO) but I can't find anything to solve this yet:
I have a Service (jobcrawler) that is started by calling startservice().
Within this service, I am starting a long-running thread, which at some point is calling a class (webservice) whose init looks like this:
public webservice(Context context) {
this.context = context;
this.db = new DatabaseHandler(this.context);
this.access_token = db.getAuthKey();
}
After some network calls, the class(webservice) receives data in a method called recieveData().
Inside recieveData I am attempting to bind to the service as follows:
if (!isBound) {
// not bound yet, then bind to the service.
Intent intent = new Intent(this, jobcrawler.class);
bindService(intent, myConnection, Context.BIND_AUTO_CREATE);
}
Now, I'm getting nullpointerexemption on the line where I call bindservice. Note, that I'm not actually attempting to do anything with the service yet. I'm just trying to bind to it.
any help would be appreciated... if I had hair I'd be pulling it out! lol
Here's some additional code that I think is relevant.
myConnection:
private ServiceConnection myConnection = new ServiceConnection() {
public void onServiceConnected(ComponentName className,IBinder service) {
Log.e("webservice", "service is connected");
MyLocalBinder binder = (MyLocalBinder) service;
myService = binder.getService();
isBound = true;
}
public void onServiceDisconnected(ComponentName arg0) {
Log.e("webservice", "service is disconnected");
isBound = false;
}
};
binder from service called MyLocalBinder:
public class MyLocalBinder extends Binder {
public jobcrawler getService() {
Log.e("Job Crawler", "returning self");
return jobcrawler.this;
}
}
service's onbind method:
private final IBinder myBinder = new MyLocalBinder();
#Override
public IBinder onBind(Intent arg0) {
Log.d("JobCrawler Service", "Service is bound");
return myBinder;
}
oh and this is where I load the class from the thread inside the service, just in case I should be using a different context or something:
private webservice ws= new webservice(getBaseContext());

I know it's a bit late, but I ran upon the same problem and maybe some googlers will be happy :)
So for me the following worked:
Call the bindService method in reference to your context:
context.bindService(intent, serviceConnection, Context.BIND_AUTO_CREATE)

Android: Getting a variable from my running service

My activity starts a Service, and when I close my app, the service continues to run.
OK, that's right. But when I open my application again, in the activity, I need to know the value of a public variable defined on the running Service(class) that I've started previously.
How can I do that?
Thanks

If you are binding your Activity to the Service, you should have an implementation of the Binder interface in your Service, e.g.
public class ServiceBinder extends Binder {
public MyService getService() {
return MyService.this;
}
}
In your Activity, create a new ServiceConnection class which will be used to give you access to your Service:
private ServiceConnection mConnection = new ServiceConnection() {
public void onServiceConnected(ComponentName className, IBinder service) {
mMyService = ((MyService.ServiceBinder)service).getService();
}
public void onServiceDisconnected(ComponentName className) {
mMyService = null;
}
};
Here the member variable mMyService will give you access to all public members of your Service class.
To create the connection, implement doBindService and doUnbindService in your Activity:
void doBindService() {
bindService(new Intent(this, MyService.class), mConnection, Context.BIND_AUTO_CREATE);
}
void doUnbindService() {
// Detach our existing connection.
unbindService(mConnection);
}
Hope this helps!

If you don't call unbindService, your activity still have connection to service and you can simply check the variable through the service's method.

You could use messenger.
As per android website
A messenger is reference to a Handler, which others can use to send messages to it. This allows for the implementation of message-based communication across processes, by creating a Messenger pointing to a Handler in one process, and handing that Messenger to another process.

getApplicationContext() ... forcing close?

I'm implementing service binding into my application. However when i start my activity which binds to the service, the application force closes. Ive pin pointed that its due to the getApplicationContext() ... Heres my code and where it is called and used...
All help is appreciated.
Thanks
private LocalService mBoundService;
private boolean mIsBound;
Context context = getApplicationContext();
private ServiceConnection mConnection = new ServiceConnection() {
public void onServiceConnected(ComponentName className, IBinder service) {
// This is called when the connection with the service has been
// established, giving us the service object we can use to
// interact with the service. Because we have bound to a explicit
// service that we know is running in our own process, we can
// cast its IBinder to a concrete class and directly access it.
mBoundService = ((LocalService.LocalBinder)service).getService();
// Tell the user about this for our demo.
Context context = getApplicationContext();
Toast.makeText(context, "serviceconnected",
Toast.LENGTH_SHORT).show();
}
public void onServiceDisconnected(ComponentName className) {
// This is called when the connection with the service has been
// unexpectedly disconnected -- that is, its process crashed.
// Because it is running in our same process, we should never
// see this happen.
mBoundService = null;
Toast.makeText(context, "serviceDisconnected",
Toast.LENGTH_SHORT).show();
}
};
void doBindService() {
// Establish a connection with the service. We use an explicit
// class name because we want a specific service implementation that
// we know will be running in our own process (and thus won't be
// supporting component replacement by other applications).
bindService(new Intent(context,
LocalService.class), mConnection, Context.BIND_AUTO_CREATE);
mIsBound = true;
}
void doUnbindService() {
if (mIsBound) {
// Detach our existing connection.
unbindService(mConnection);
mIsBound = false;
}
}
#Override
protected void onDestroy() {
super.onDestroy();
doUnbindService();
}

in order to bind service with activity,instead of using getApplicationContext(), you should use getBaseContext() or this keyword

Wait on startService before bindService

It is my understanding that if I want a service to run even if nothing is bounded to it, then it must first be started with startService(Intent i).
My question is WHAT IF I want to bind to the service immediately after I start it, would the following code guarantee the service is created with startService()?
Static method within the service class:
public static void actStart(Context ctx) {
Intent i = new Intent(ctx, BGService.class);
i.setAction(ACTION_START);
ctx.startService(i);
}
The binding activity:
BGService.actionStart(getApplicationContext());
bindService(new Intent(this, BGService.class), serviceConnection, Context.BIND_AUTO_CREATE);

I am not sure what you are trying to do here, but "Context.BIND_AUTO_CREATE" creates the service then binds to the service even if it hasn't been started.
Now if you want to access it immediately after binding, you can use the onServiceConnected() method of the serviceConnection:
new ServiceConnection() {
#Override
public void onServiceConnected(ComponentName className,
IBinder service) {
//put your code here...
} ...

To add to Bugdayci's answer, a complete example is as follows:
ServiceConnection myConnection = new ServiceConnection() {
#Override
public void onServiceConnected(ComponentName className,
IBinder service) {
... your code that needs to execute on service connection
}
#Override
public void onServiceDisconnected(ComponentName name) {
... your code that needs to execute on service disconnection
}
};
Intent intent = new Intent(this, TheServiceClassName.class);
bindService(intent, myConnection, Context.BIND_AUTO_CREATE);
...
Without the bindService at the end, the onServiceConnected() code will not execute.