threaded service with better lifetime management

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Please excuse the long report - but it is probably necessary to explain such a 
large patch (which I've attached as a hg 'bundle' against the current trunk)

I noticed some strangeness in how TalkMyPhone (and hence GTalkSMS) works with 
its service, particularly related to the lifetime management and how other 
parts of the program interact with it.  To give a few practical examples:

* The UI thread is blocked while the xmpp connection is established or torn 
down.  In extreme cases, Android will notice this and offer to force-close the 
"hung" process.

* It is possible to see exceptions raised by the various calls to 
unbindService() due to the service never having been previously bound in that 
context (let me know if you want a specific example to see this)

* Similarly to above, the ActivityManager log will sometimes write a 
stack-trace with an error messaging saying our activity leaked a 
ServiceConnection.

I decided to have a go at fixing that :)  I made some significant structural 
changes which I'll outline below:

* The service is implemented with a thread+queue system along the lines of 
'IntentService' (but alas, IntentService itself wasn't flexible enough to use 
directly).  All interaction with the XmppManager now happens on a worker 
thread.  Nothing on the main thread blocks at all meaning the UI is noticeably 
snappier.

* All communication with the worker thread is done using Intent objects.  The 
'instance/getInstance()' statics have gone (yay!) - everyone who used to use 
that now uses Intents.

* All communication from the worker thread to the rest of the system is done 
using broadcast receivers.  Eg, the XmppListener class has been removed and 
replaced with generic broadcasts when connection-status changes, a message is 
received or presence changes.  The service no longer needs to delegate to other 
listeners - android manages all that for free.

* I removed the CallReceiver class and arrange to hook up telephony 
notifications only when our service is running, preventing the GTalkSMS process 
from starting every time a call is received just to notice we are not connected 
and to do nothing.

* The above all enables the service lifetime issues to be made much cleaner.  
stopService() and onDestroy() are never explicitly called - android can kill 
the process when it is necessary.  The service isn't 'destroyed' (although it 
is 'stopped') when it is disconnected, meaning activities can bind to the 
service in the "usual" way without fear the service went away just because the 
connection died.

* The XmppManager state of "QUIT" has been removed as it is no longer 
necessary.  A new state of WAITING_TO_CONNECT has been added which indicates an 
automatic connection attempt is pending (due to either lack of network 
capability or a retry cycle).  The service remains in the foreground while in 
this state to avoid premature stopping of the service.

Another side-effect of this set of changes is that if the XmppManager does 
hang, it doesn't cause the entire app to hang - just the worker thread gets 
stuck.  A side-effect of this though is that android will no longer offer the 
"force close" dialog as the app's main thread is still working perfectly.  This 
is still a better result when taking the widget into consideration, where a 
hang is much more noticeable.

The attached patch set is very large, but I think very worthwhile.  I 
understand it may take a little time to go through all the changes - please ask 
me if you need any clarification.  I'm also happy to remerge the patches should 
other changes be made on the trunk while this is being reviewed.  FWIW, I have 
tested it quite thoroughly.

Original issue reported on code.google.com by skippy.hammond@gmail.com on 29 Dec 2010 at 6:45

Attachments:

• service-changes.bundle

[GoogleCodeExporter]

Original comment by Florent....@gmail.com on 29 Dec 2010 at 8:35

• Changed state: Started
• Added labels: Priority-High, Type-Enhancement
• Removed labels: Priority-Medium, Type-Defect

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Original comment by Florent....@gmail.com on 29 Dec 2010 at 11:02

• Changed state: Fixed

[GoogleCodeExporter]

Original comment by fschm...@gmail.com on 25 Aug 2011 at 7:51

• Changed state: Deployed