I'm trying to implement a pattern of accessing data source, independently
if it's local or remote, using a content provider.
So, inside the content provider, for example in the query method:
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {...}
I want to, check if data is stored locally, if not, then call the
webservice, on response save and return it. Typical request process with a
local cache.
Now to get the data from the webservice, I wanted to use a service. Because
I want that once started, it will receive and process the response, even if
the user exits the app / the system kills it, etc.
Note: I don't need to use anything synchronous here, since I'm already
running the query to the content provider asynchronouly
(AsyncQueryHandler). So I think I have to use Service instead of e.g.
IntentService.
The idea with the service is to have a method to call the webservice:
public WebserviceResponse callWebservice(params) {...}
And in ContentProvider.query():
WebserviceResponse response = myService.callWebservice(params);
But the problem is that I can't find how to ensure that the service is
already bound before the first query. If I bind it in
ContentProvider.onCreate:
@Override
public boolean onCreate() {
final Context context = getContext();
dbHelper = new DatabaseHelper(context);
context.bindService(new Intent(context, MyService.class), mConnection,
Context.BIND_AUTO_CREATE);
return true;
}
Where mConnection is:
private ServiceConnection mConnection = new ServiceConnection() {
public void onServiceConnected(ComponentName className, IBinder binder) {
myService = ((MyService.MyBinder) binder).getService();
}
public void onServiceDisconnected(ComponentName className) {
myService = null;
}
};
And I do a query using this content provider in my activity's onCreate(),
the service is not bound yet and I get an exception when I try to use it.
A way around I can think of, is to call the webservice directly - without a
service - from the content provider. This will be synchronous and I can
process the response without problems there. But it has mentioned
disadvantage that the call can be interrupted and the data not processed.
It's not the end of the world - the next time the user opens the app, the
webservice would be called again. But I still would like to not have it
that way.
A second possibility I can think of, is to invert this logic and do the
access to the content provider in a (asynchronous) service. But here I have
a different problem, which is that, afair, the async service
(IntentService) communicates with the caller though with IPC and this is
not supposed to pass large amounts of data. So I would have again to wrap
this in some other logic which after service is finished checks a flag and
retrieves data, this time directly from the content provider. This would
also mean to start a second async query.
I already came up with an architecture that works, but it's quite complex.
It:
1. Does async query to the content provider
2. If there's no data, starts an IntentService to get it from remote.
3. After the service finishes it returns a flag, and then, does again async
query to get the data which was saved by the webservice.
I would like to simplify it, that's why I'm asking this.
So is there any way that I can use the service in the content provider, or
any other approach, or advice you would recommend?
--
You received this message because you are subscribed to the Google
Groups "Android Developers" group.
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to
[email protected]
For more options, visit this group at
http://groups.google.com/group/android-developers?hl=en
---
You received this message because you are subscribed to the Google Groups
"Android Developers" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/groups/opt_out.
