到目前为止，您不能使用

As of now, you can't use SAM conversion for interfaces defined in Kotlin. There are a couple things you can do to solve your problem though.

1. 如果您使用Java定义接口，则SAM转换将开始工作，并且您的当前代码将无需任何其他更改即可工作.

1. If you define your interface in Java, SAM conversion will start working, and your current code will work without any other changes.

如果要使用接口作为fetch_data方法的参数，并且希望使用Kotlin编写该接口，则必须传入实现该接口的object有点冗长，类似于Java的解决方案:

If you want to use an interface as the parameter of the fetch_data method, and you want it to be written in Kotlin, you'll have to pass in an object that implements it, which is a slightly verbose, Java-like solution:

jmManager.fetch_data(object: OnTaskCompleted {
    override fun onTaskCompleted(theJsonArray: JSONArray) {
        // ...
    }
})

fun fetch_data(callback: (JSONArray) -> Unit) { 
    // ...
    listener?.onTaskCompleted(response)
    callback(response)
    // ...
}