CODEWITHSUNDEEP
androidkotlin
Zorgan
Zorgan

Reputation: 9123

Why does the class in Intent have the "::class.java" suffix?

An intent in Kotlin:

val intent = Intent(this, OtherActivity::class.java)

why can't it just be:

val intent = Intent(this, OtherActivity)

?

Upvotes: 2

Views: 1055

Answers (4)

Zoe - Save the data dump
Zoe - Save the data dump

Reputation: 28228

Using ::class, Kotlin supplies a KClass, which can be used for various things. However, there are still Java packages which use Class instead, and among those is Intent. A KClass is not a Class, which means Kotlin needs to have a way to access the regular Java Class.

The Intent class is originally written in Java, which means it uses a Class. OtherActivity::class returns a KClass, and a KClass can't be passed as a Class.

SomeClass::class.java exists for interop purposes. You can also use a Class instead of KClass in your Kotlin code; you won't get warnings about that like you'd get about for an instance Object over Any. But you still periodically need a Class with Java interop.

Why specifically they went with ::class.java is not something anyone can answer, aside the developers of the language itself.

Upvotes: 2

Eric Martori
Eric Martori

Reputation: 2975

if you are okay with a little bit of namespace polution and this is a real concern in your team you can allways declare the following top level function:

inline fun <reified T> Intent(context: Context){
    return Intent(context, T::class.java)
}

Which you would call doing the following:

val intent = Intent<MyActivity>(this)

Or if you want you can declare it as an extension function on Context:

inline fun <reified T> Context.Intent(){
    return Intent(this, T::class.java)
}

An use it directly like this:

val intent = Intent<MyActivity>()

Upvotes: 1

Leo Aso
Leo Aso

Reputation: 12463

The second argument of that Intent constructor requires the class of the Activity you want to create. While it would be convenient to get the class just by using the class name OtherActivity, Java (and Kotlin) syntax does not support this.

Instead, Java provides the .class syntax (OtherActivity.class) and Kotlin provides::class for the Kotlin class, and ::class.java (OtherActivity::class.java) for the Java class, which is what the Intent constructor needs.

Upvotes: 5

jden
jden

Reputation: 2288

Because Intent is a java class and expects an Android Context and a Java Class (The activity) as the arguments.

Upvotes: 1

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