Hi guys, I have a question to use AsyncTask in Kotlin. I want to post a data to server and I created a class which override AsyncTask.

open class PostTask() : AsyncTask<String, Void, Void>() {
        override fun doInBackground(vararg params: String?): Void {
            NetworkModule().getRetrofitClient(URL_TEST).create(PostService::class.java)
                    .postData(params[0])
    }
}

Android studio shows [TYPE_MISMATCH] error for

params[0]

, and if I change

String?

to

String

, the parameter’s type of doInBackground, [NO_RETURN_IN_FUNCTION_WITH_BLOCK_BODY] error is happened. 1. How to compare type

Type?

and

Type

? 2. How to write return statement, if return type was

Void

?

Unit

type in Koltin corresponds to

void

type in Java, try this:

open class PostTask() : AsyncTask<String, Unit, Unit>() {
    override fun doInBackground(vararg params: String) {
        NetworkModule().getRetrofitClient(URL_TEST).create(PostService::class.java)
                .postData(params[0])
    }
}

Thank a lot, clear every errors