Android：发出从RecyclerView删除最后一个项目的问题

Question

I am using the RecyclerView in the following manner to show a list of Places items that are updated in SQLite DB .

The items are deleted fine and updated as i swipe them . But when I swipe to delete the last item , it comes back in the view . When i close the app and reopen the app , the item is deleted though .

But when item is swiped to delete , in that instance of app running , the item is not deleted from view even after swiping multiple times .

@Override
public void onSwiped(RecyclerView.ViewHolder viewHolder, int swipeDir) {
     int swipedPosition = viewHolder.getAdapterPosition();
     PlaceListAdapter adapter = (PlaceListAdapter) mRecyclerView.getAdapter();

     int pos = viewHolder.getAdapterPosition();
     // Build appropriate uri with String row id appended
     String stringId = places.get(pos).getId();

     Log.d("testhro", stringId);

     Uri uri = PlaceContract.PlaceEntry.CONTENT_URI;
     uri = uri.buildUpon().appendPath(stringId).build();

     Log.d("testhhd", uri.toString());
     // COMPLETED (2) Delete a single row of data using a ContentResolver
     getContentResolver().delete(uri, null, null);
     mAdapter.notifyDataSetChanged();
     refreshPlacesData();

}

refreshPlacesData()

 private void refreshPlacesData() {
        Uri uri = PlaceContract.PlaceEntry.CONTENT_URI;
        Cursor data = getContentResolver().query(
                uri,
                null,
                null,
                null,
                null);

        if (data == null || data.getCount() == 0) return;

        Log.d("countIs", String.valueOf(data.getCount()));

        List<String> guids = new ArrayList<String>();
        while (data.moveToNext()) {
            guids.add(data.getString(data.getColumnIndex(PlaceContract.PlaceEntry.COLUMN_PLACE_ID)));
        }
        PendingResult<PlaceBuffer> placeResult = Places.GeoDataApi.getPlaceById(mClient,
                guids.toArray(new String[guids.size()]));
        placeResult.setResultCallback(new ResultCallback<PlaceBuffer>() {
            @Override
            public void onResult(@NonNull PlaceBuffer places) {
                mAdapter.swapPlaces(places);
                MainActivity.this.places = places;
                mGeofencing.updateGeofencesList(places);
                if (mIsEnabled) mGeofencing.registerAllGeofences();
            }
        });
    }

Am I missing something? Thanks.

EDIT : i tried updating adapter instead of mAdapter , but still no change

EDIT 2

public void swapPlaces(PlaceBuffer newPlaces) {
        mPlaces = newPlaces;
        if (mPlaces != null) {
            // Force the RecyclerView to refresh
            this.notifyDataSetChanged();

        }
    }

Note : I also verified the loggers :

D/countIsZero: true (inside refreshPlacesData())

Answer 1

You should refresh your View after changing dataset.

   MainActivity.this.places = places; // Data set changed
   PlaceListAdapter adapter = (PlaceListAdapter) mRecyclerView.getAdapter();
   adapter.notifyDataSetChanged();

or you should change order of

   mAdapter.notifyDataSetChanged(); // Notify later
   refreshPlacesData(); // Refresh first

Firstly change dataset and then notify adapter.

Answer 2

Solved..

As i was deleting the last item , the data count would become 0 , in which case i was currently just returning.

So instead of that , following is my addition inside refreshPlacesData() :

  if (data.getCount() == 0) {
            Log.d("countIsZero","true");
            mAdapter.swapPlaces(null);
            return;
        }

and

 public void swapPlaces(PlaceBuffer newPlaces) {
        mPlaces = newPlaces;

        if(mPlaces==null)
        {
            Log.d("mPlaceNull","true");
            this.notifyDataSetChanged();
            return;
        }

Weirdly , only thing happening here is this.notifyDataSetChanged(); being called on adapter object , but if i use it this way and skip calling of swapPlaces() , it does not work ie

if (data.getCount() == 0) {
            Log.d("countIsZero","true");
            mAdapter.notifyDataSetChanged();
            return;
        }

doesn't work.