How can i initialize Room database from Presenter (MVP)

Question

I'm trying to implement Room database in my project, but i have a problem. I am using MVC pattern and in presenter, I want to initialize room database. But to do that, I need a context, which presenter should not have. What I am doing wrong?

My Room DB:

@Database(entities = {SportEvent.class},version = 1)
public abstract class RecommendedEventsDB extends RoomDatabase {

    private static RecommendedEventsDB INSTANCE;

public abstract SportEventDao sportEventDao();

//singleton instance of database
public static RecommendedEventsDB getRecommendedEventsDB(Context context){
    if(INSTANCE == null) {
        INSTANCE = Room.databaseBuilder(context.getApplicationContext(),
                RecommendedEventsDB.class, "recommended_Events")
                .allowMainThreadQueries() //need to be deleted, for testing purpose only!!!
                .build();
    }
    return INSTANCE;
    }
}

And in Presenter i would like to initiate DB:

RecommendedEventsDB db = RecommendedEventsDB.getRecommendedEventsDB(context);

but i have not context...

Can you help me please?

Answer 1

There was a talk about Fragment s (Google I/O 2016) according to which

Fragments are part of the ? in MV?

(at about 9:30 min.) And Fragment s do have a Context as long as they are attached to an Activity .

An interesting point of view.

But if one insists on having an Android -free Presenter, then one can use an interface (or two):

A Presenter needs an interface - let's call it ViewInterface - to communicate with the Fragment or Activity or View to which it belongs. Without this ViewInterface , nothing can happen in the "real world".

The database (as a means of physically storing data and accessing stored data) is very much part of this "real world", so it is only fitting that the Presenter asks its ViewInterface to make someone or something instantiate the data storage facility and please come back with another interface so the Presenter can cause all the CRUD operations to happen. Let's call this one DatabaseInterface .

So basically, you have two interface s. The first one could be implemented by a Fragment or View

interface ViewInterface{
    // ...        


    DatabaseInterface getDatabaseInterface();
}

The second one can be implemented by another class which will then manage the database operations

interface DatabaseInterface{
    void insertNewCustomer(Customer customer);
    void deleteCustomer(long customerDbId);
    List<Customer> findAllCustomers();
    // ...

}