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kotlinkotlin-android-extensions
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Reputation: 1456

Kotlin Activity cannot be extended. This type is final, so it cannot be inherited

I have created a Kotlin Activity, but I am not able to extend the activity. I am getting this message: This type is final, so it cannot be inherited from. How to remove final from Kotlin's activity, so it can be extended?

Upvotes: 74

Views: 34707

Answers (4)

Fortran
Fortran

Reputation: 2336

class Base

Simple add open for super/parent class:

open class Base

Upvotes: 1

Waqar UlHaq
Waqar UlHaq

Reputation: 6422

In Kotlin, the classes are final by default that's why classes are not extendable.

The open annotation on a class is the opposite of Java's final: it allows others to inherit from this class. By default, all classes in Kotlin are final. Kotlin - Inheritance

open class Base(p: Int)

class Derived(p: Int) : Base(p)

Upvotes: 26

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Reputation: 1456

By default the Kotlin activity is final, so we cannot extend the class. To overcome that we have to make the activity open so that, it can be extendable.

as like open class BaseCompatActivity : AppCompatActivity() { }

Upvotes: 28

Girish Arora
Girish Arora

Reputation: 996

As per Kotlin documentation, open annotation on a class is the opposite of Java's final. It allows others to inherit from this class. By default, all classes in Kotlin are final.

open class Base {
    open fun v() {}
    fun nv() {}
}

class Derived() : Base() {
    override fun v() {}
}

Refer :https://kotlinlang.org/docs/reference/classes.html

Upvotes: 92

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