Implementing Java Interface - Kotlin

Question

Just getting started with Kotlin and and I have read the official documentation, I am having issues implementing an interface from a library in kotlin.

Here is the interface in java :

public interface ResultCallBack {
    void detailsRetrieved(Obj var1, AnotherInterface var2);

    void anotherDataRetrieved(int var1, AnotherInterface var2);
}

the method I am calling from kotlin is like this :

 public static void startLibActivity(Context context, ResultCallBack callback) {
        sLuhnCallback = callback;
        context.startActivity(new Intent(context, Library.class));
    }

how do i call startLibActivity from kotlin and implement ResultCallBack as well

I think I am stuck with this trial :

Library.startLibActivity(activity, {})

I have tried many possibilities within {} , still having issues with the right implementation.

What did you tried?

talex
– talex

2017-07-10 16:17:34 +00:00
Commented Jul 10, 2017 at 16:17 — talex
– talex, Commented Jul 10, 2017 at 16:17
What does your Kotlin code look like?

Makoto
– Makoto

2017-07-10 16:19:11 +00:00
Commented Jul 10, 2017 at 16:19 — Makoto
– Makoto, Commented Jul 10, 2017 at 16:19
@Makoto I just updated the question

Belvi Nosakhare
– Belvi Nosakhare

2017-07-10 16:22:29 +00:00
Commented Jul 10, 2017 at 16:22 — Belvi Nosakhare
– Belvi Nosakhare, Commented Jul 10, 2017 at 16:22

holi-java · Accepted Answer · 2017-07-10 16:28:59Z

9

Since your java interface is not a SAM Functional Interface, so you can't using lambda expression {} in Kotlin directly.

You can implement a Java interface in Kotlin, for example:

class KotlinResultCallBack : ResultCallBack {
    override fun detailsRetrieved(var1: Obj?, var2: AnotherInterface?) = TODO()

    override fun anotherDataRetrieved(var1: Int, var2: AnotherInterface?) = TODO()
}

Then you can call the startLibActivity method as below:

startLibActivity(context, KotlinResultCallBack())

You can also use an object expression to create an anonymous class instance which implements a Java interface, for example:

startLibActivity(context, object : ResultCallBack {
    override fun detailsRetrieved(var1: Obj?, var2: AnotherInterface?) = TODO()

    override fun anotherDataRetrieved(var1: Int, var2: AnotherInterface?) = TODO()
})

edited Jul 10, 2017 at 16:28

answered Jul 10, 2017 at 16:22

holi-java

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2 Comments

Belvi Nosakhare Over a year ago

thanks. This works ! Will accept the answer in 5 mins

holi-java Over a year ago

@belvi Not at all.

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