MvpLceActivity can't see Dagger2 injections

[jemshit]

I have MyModule.java which provides a Presenter for Activity:

    @Provides
    public MyPresenter getMyPresenter(){
        return new MyPresenter();
    }

There is MyComponent.java which has:

public interface MyComponent {
    void inject(MyActivity act);

    MyPresenter getMyPresenter();
}

Now i am trying to inject that Presenter in MyActivity and use it:

public class MyActivity extends MvpLceActivity... {
@Inject MyPresenter myPresenter;
...
private void injectDependencies(){
    ....
}

 @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        injectDependencies();
        ....
}
@NonNull @Override
    public MyPresenter createPresenter() {
        return myPresenter;
}
...
}

It shows error:

java.lang.NullPointerException: Presenter is null! Do you return null in createPresenter()?

[sockeqwe]

You have to call injectDependencies() before super.onCreate() because the super.onCreate() will call createPresenter() internally.

Also, there is already a field called presenter if you extend from a Mosby base class like MvpLceActivity. So in your MyActivity class you have two variables pointing at the same presenter instance myPresenter and ´presenter. The later one comes as protected field fromMvpLceActivity`.

I would recommend you to take a slightly different approach regarding dependency injection with dagger2. I would recommend to change your code to something like this:

public class MyActivity extends MvpLceActivity... {
  private MyComponent component;
  ...

  private void injectDependencies(){
     myComponent = DaggerMyComponent.create();    
    ....
  }

 @Override
  public void onCreate(Bundle savedInstanceState) {
        injectDependencies();
        super.onCreate(savedInstanceState);
        ....
  }

  @NonNull @Override
  public MyPresenter createPresenter() {
        return component.getPresenter();
  }
  ...
}

[jemshit]

👍

[epetrenko]

@sockeqwe, @jemshit

Let me share a solution, which I use for the case if dagger-android extension is used.

We can use Provider<T> injection. Code will look like the following:

public class MyActivity extends MvpLceActivity... {
  @Inject Provider<MyPresenter> myPresenterProvider;
  ...

 @Override
  public void onCreate(Bundle savedInstanceState) {
        AndroidInjection.inject(this);
        super.onCreate(savedInstanceState);
        ....
  }

  @NonNull @Override
  public MyPresenter createPresenter() {
        return myPresenterProvider.get();
  }
  ...
}

Here we do injection in Activity by calling just AndroidInjection.inject(this) and don't need to have component instances.