How to use ExecutorService with Android Room?

Question

I am using ExecutorService with Android Room to avoid multiple in insetAsyncTasks. I was using Debanjan example from this post: link but I modified it a bit.

Problem is that I don't get any exception but nothing is inserted.

DaoAsyncProcessor:

public abstract class DaoAsyncProcessor<T> {

public interface DaoProcessCallback<T>{
    void  onResult(T result);
}

private DaoProcessCallback daoProcessCallback;

public DaoAsyncProcessor(DaoProcessCallback daoProcessCallback) {
    this.daoProcessCallback = daoProcessCallback;
}

protected abstract T doAsync();

public void start(){
    new DaoProcessAsyncTask().execute();
}

private class DaoProcessAsyncTask extends AsyncTask<Void, Void, T> {

    @Override
    protected T doInBackground(Void... params) {
        return doAsync();
    }

    @Override
    protected void onPostExecute(T t) {
        if(daoProcessCallback != null)
            daoProcessCallback.onResult(t);
    }
}
}

Repository:

public void createUpdate(final Projects item){
    EncertDatabase.databaseWriteExecutor.execute(() ->{
        if(item!=null){
            if(item.getId()==null){
                encertDAO.insert(item);
            }
            else {
                encertDAO.update(item);
            }
        }else {
            Log.e("Krkec", "Item was null");
        }

    });
}

Database:

public abstract class EncertDatabase extends RoomDatabase {
private static  volatile EncertDatabase INSTANCE;
public  abstract EncertDAO encertDAO();

private static final int NUMBER_OF_THREADS = 4;
public static final ExecutorService databaseWriteExecutor =
        Executors.newFixedThreadPool(NUMBER_OF_THREADS);

public static  EncertDatabase getDatabase(final Context context){
    if(INSTANCE== null){
        synchronized (EncertDatabase.class){
            if (INSTANCE ==null){
                INSTANCE = Room.databaseBuilder(context.getApplicationContext(), EncertDatabase.class,"encertDatabase").fallbackToDestructiveMigration().build();
            }
        }
    }
    return INSTANCE;
}
}

What am I doing wrong?

Answer 1

assign executor service instance to db builder instance using setQueryExecutor

Answer 2

INSTANCE = Room.databaseBuilder(context.getApplicationContext(), EncertDatabase.class,"encertDatabase").setQueryExecutor(databaseWriteExecutor).fallbackToDestructiveMigration().build();

when you want to make queries use:

INSTANCE.getQueryExecutor().execute(()->{//your query here}); }

for some reason directly using Executor Service does not work.