Question

Can someone just explain to me what is runQueryOnBackgroundThread as I already read through some sources but still not understand with it?

@Override
public Cursor runQueryOnBackgroundThread(CharSequence constraint){
    FilterQueryProvider filter = getFilterQueryProvider();
    if (filter != null){
        return filter.runQuery(constraint);
    }

    Uri uri = Uri.withAppendedPath(
                ContactsContract.CommonDataKinds.Phone.CONTENT_FILTER_URI, Uri.encode(constraint.toString()));

    return content.query(uri, CONTACT_PROJECTION, null, null, null);
}

Answer 1

A handle of my Activity in the Adapter and the runQuery call in the filter makes a call to startManagingCursor on the Activity whenever the runQuery is called. This is not ideal because a background thread is calling startManagingCursor and also there could be a lot of cursors remaining open until the Activity is destroyed.

I added the following to my Adapter which has a handle on the Activity it is used within

@Override 
public void changeCursor(Cursor newCursor) { 
Cursor oldCursor = getCursor(); 
super.changeCursor(newCursor); 
if(oldCursor != null && oldCursor != newCursor) { 
    // adapter has already dealt with closing the cursor 
    activity.stopManagingCursor(oldCursor); 
} 
activity.startManagingCursor(newCursor); 
} 

This makes sure that the current cursor used by the adapter is also managed by the activity. When the cursor is closed by the adapter management by the activity is removed. The last cursor held by the adapter will be closed by the activity by way of it still be managed by the activity.