Content Provider w/ Cursor - Gets Killed (how to n

问题:

I have a content provider in on apk which is providing Rest Based Search results for multiple client apps.

Basically, the client requests a cursor via content resolver, then fires an intent service request to trigger the search..

In the provider, the cursor is returned to a table, and each intent service request populates the corresponding table, and triggers a NotifyDataSetChanged.

Works really well.. The only issue I am having is that if the Provider is killed for some reason (tested by doing pkill -9 com.myprovider.name) the cursor on the client apk does not change, but the app is not notified that the provider went away, and would need to re-connected to the db.. So it will continue to fire off service intents, and the cursor never gets updated b/c it is no longer tied to the underlying db..

I went through our code to try and see if we were catching some exceptions, that maybe hiding the underlying issue, but I am not seeing it..

I tried explicitly doing a cursor.close() in the provider in finalize / onLowMemory / shutdown().. None appear to get triggered.

I noticed that this happens in the logcat

09-10 13:58:03.015: I/ActivityThread(4268): Removing dead content provider: com.myprovider.name (called from the calling app)

Any way to get this notification from the calling app?

回答1:

So after some research, I have a workable solution, but would if anyone has any other suggestions, they would be appreciated.

Due to the fact we are using a contentProvider to get a cursor, then just updating the back end data via IntentService. We grab the cursor when our user types the first character in of their search, if the cursor count = 0, then we show an empty list message, otherwise we display the list of items in that cursor..

** NOTE: Some of the cursor handling may need to be tweaked a bit, I did not see any crashes w/ our Adapter having a cursor ripped out and becoming null, but your mileage may vary.. ( This is more about using the contentProviderClient() )

** NOTE: Per the documentation, you MUST release the contentProviderClient() when not in use anymore.

Since a content provider should be returning a type, we can do the following..

So we define a member variable

private ContentProviderClient contentProviderClient = null;

Then when our user changes the search string we end up calling

public void setFilter( String searchFilter ) {
   searchedString = !TextUtils.isEmpty(filter) ? filter : "";

   boolean reload = false;               // Reloads content provider

   // contentProvider is null on first connection, assumed to be up on 
   // subsequent connections as we only close the cursor and 
   // contentProviderClient when we exit

   if (contentProviderClient != null) {
      try {
      // getType will throw an exception if the instance of the 
      // contentProvider went away (killed by user/memory collection etc)

         contentProviderClient.getType(searchFactoryUri);
      } catch (RemoteException e) {
         if( searchAdapter != null ) {
            Cursor cursor = searchAdapter.getCursor();
            cursor = null; 
            reload = true;
            contentProviderClient.release();
         }
      }
   }

   // This is for first search initialization or reloading cursor 
   // if the content provider went away for some unknown reason.

   if( this.searchAdapter == null || reload ){
      Cursor cursor = getActivity().getContentResolver().query(
            MY_URI,
            null,
            null,
            null,
            null);

   contentProviderClient = getActivity()
             .getContentResolver()
             .acquireContentProviderClient(MY_URI);

   cursor.setNotificationUri(getActivity.getContentResolver(), MY_URI);

   // DO what ever you need to after getting cursor, a cursor loader
   // would be a better implementation here, but simplifying it as 
   // I don't want to over-complicate the example.

   myList.setAdapter(searchAdapter);

   }
   getActivity().startService(MyUtil.getSearchIntent( MY_URI, searchedString );
}

@Override
public void onDestroy() {
   super.onDestroy();
   // Cleanup adapter, cursor, provider client
   if (searchAdapter != null) {
      searchAdapter.changeCursor(null); // Closes existing cursor 
   }
   if (contentProviderClient != null) {
     contentProviderClient.release();  // Release client
   }
}