how to deal with the Generic in Kotlin from java code

Question

code in java:

public interface MvpPresenter<V extends MvpView> {
  public void attachView(V view);
  public void detachView(boolean retainInstance);
}

when I write in kotlin:

interface MvpPresenter<out MvpView> {
    fun attachView(view: MvpView)
    fun detachView(retainInstance: Boolean)
}

fun attachView(view: V) compile error!
So How can I deal with ? extend T in kotlin???

how to deal with upper bound but can use as java code? – user3163839 May 15 '18 at 10:03 — user3163839, May 15 '18 at 10:03

Sweeper · Answer 1 · 2018-05-15T09:57:55.780

0

You use <V: MvpView>!

Also change the declaration of attachView to:

fun attachView(view: V)

That's defining an upper bound for the generic type V.

So How can I deal with ? extend T in kotlin???

That seems to be somewhat unrelated because you are now talking about generic wildcards. In kotlin, <? extends MvpView> would be <out MvpView>

edited May 15 '18 at 09:57

answered May 15 '18 at 09:46

Sweeper

but if I use in, I make a new class LoginView : MvpView, the LoginView is not include in MvpView – user3163839 May 15 '18 at 09:51
@user3163839 I realised that was wrong and edited. Did you not see it? – Sweeper May 15 '18 at 09:55
Thanks a lot, I will try again – user3163839 May 15 '18 at 09:56
I am sorry ,I mean how to deal with upper bound but can use as java code? – user3163839 May 15 '18 at 10:04
@user3163839 can it not be used as Java code with my solution? What error does it produce? – Sweeper May 15 '18 at 10:05
class BaseActivity
> : AppCompatActivity()
– user3163839 May 15 '18 at 10:21

1 Answers1