List reading empty when inside doInBackground of AsyncTask

Issue

I am trying to read a list of integers inside of the doInBackground of AsyncTask. When I pass the list into the constructor of AsyncTask, it is full. But, by the time I get to the doInBackground function, it is empty. Any ideas?

public class floatingActionButtonClickListener implements View.OnClickListener{

    @Override
    public void onClick(View v) {
        if(mAdapter.getDeleteModeStatus()){
            // Delete items from database
            ArrayList<Integer> IDsToDelete = mAdapter.getJournalIDsToDelete();
            new DeleteDatabase().execute(IDsToDelete);

            // Turn FAB back to regular button
            mFAB.setImageResource(R.drawable.baseline_add_white_48); // Turn FAB to delete button

            // Disable delete mode
            mAdapter.exitDeleteMode();

            // Load database
            new LoadDatabase().execute();
        }
        else{
            Intent intent = new Intent(getBaseContext(), AcitivtyJournal.class);
            int journalType = Constants.JOURNALTYPE_FULL;
            intent.putExtra(Constants.JOURNAL_TYPE, journalType);
            startActivity(intent);
        }
    }
}

private class DeleteDatabase extends AsyncTask <ArrayList<Integer>, Void, Void> {
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        mProgressBarHolder.setVisibility(View.VISIBLE);
    }

    @Override
    protected Void doInBackground(ArrayList<Integer>... arrayLists) {
        ArrayList<Integer> IDsToDelete = arrayLists[0];

        AppDatabase db = Room.databaseBuilder(getApplicationContext(), AppDatabase.class, "JournalEntries")
                .build();

        for(Integer idToDelete : IDsToDelete){
            db.mJournalEntriesDao().deleteCompleteJournalEntry(idToDelete);
        }

        return null;
    }

    @Override
    protected void onPostExecute(Void aVoid) {
        mProgressBarHolder.setVisibility(View.GONE);
    }
}

}

Solution

Figured it out. Posting for people in the future who may have similar questions.

Embarrasingly enough, the ArrayList<Integer> was coming empty because I was deleting it in the function mAdapter.exitDeleteMode(); after I call AsyncTask().execute().

I was not aware that when I send the list to the AsyncTask it was the exact address of the list and not just a new list (that is, until I posted the comment above, and then it clicked). I think I got that train of thinking from C++ or another language. I don't remember which.

Solution: The solution I came up with is to just move mAdapter.exitDeleteMode() into of onPostExecute()instead of having it in the onClick() method.

Another Potential Solution: I believe another solution that would work (but I did not test) would be to just insert a new ArrayList<Integer> () into the AsyncTask

Answered By - Rayaarito