Model receive context on Android MVP

Question

I have a sqlite database, to use precise context, however, sending the context to the presenter and then pro model would be a violation of MVP, because it is part of the view, is part of Android. How I would use context without violating MVP?

In case, pass to the presenter would be like this:

interface Model {
    String getUser();
    String getPassword();
}

interface View {
    void showToast(String message);
    void emptyUsuarioEditText();
    void emptyPasswordEditText();
    Context getContext();
}

interface Presenter {
    void login(String user, String password);
    Context getContext();
}

Answer 1

Actually, you don’t need a Context proper. What you need is a reference to a class that extends SQLiteOpenHelper.

Let’s say, a class Database:

public class Database extends SQLiteOpenHelper {
...
}

This class, in turn, needs a Context.

There are several different ways you pass a reference to this Database for your model. You can create a method static in your class Application that returns to you an instance of the class Database.

public class MyApplication extends Application {
    private static MyApplication sInstance;

    @Override
    public void onCreate() {
        super.onCreate();
        sInstance = this;
    }

    public static Database getDatabase() {
        return new Database(getContext());
    }

    public static Context getContext() {
       return sInstance.getApplicationContext();
    }
}

So just do it in your Model (or Presenter and send it to the Model):

MyApplication.getDatabase();

Although it works I don’t really like this approach. I don’t think it’s right to do it in the Application class.

So you could have a class, say: Injection. Where you perform "DI in hand".

public final class Injection {

    private Injection() {
        throw new IllegalStateException(Injection.class.getSimpleName() + " cannot be instantiated!");
    }

    public static Database provideDatabase() {
        return new Database(MyApplication.getContext());
    }
}

Another alternative is if you use Dagger, for example, let it do the class automatic dependency injection Database in his Model.