Android: pass function reference to AsyncTask

Question

I\'m new to android and very used to web developing. in javascript when you want to perform an asynchronous task you pass a function as an argument (a callback):

<         


        

Answer 1

in Kotlin

Firstly, create class AsyncTaskHelper as below.

class AsyncTaskHelper() : AsyncTask, Void, Boolean>() {

    var taskListener: AsyncListener? = null

    override fun doInBackground(vararg params: Callable?): Boolean {
        params.forEach {
            it?.call()
        }
        return true
    }

    override fun onPreExecute() {
        super.onPreExecute()
    }

    override fun onPostExecute(result: Boolean?) {
        super.onPostExecute(result)
        taskListener?.onFinished(result as Any)
    }

}

interface AsyncListener {
    fun onFinished(obj: Any)
}

the code below you can use when you want to use async task.

    AsyncTaskHelper().let {
        it.execute(Callable {
                //this area is the process do you want to do it in background
                // dosomething()
                }
            }
            null
        })
        it.taskListener = object : AsyncListener{
            override fun onFinished(obj: Any) {
                // this area is for the process will want do after finish dosomething() from Callable callback


            }

        }

From the code above. if you want to separate your process to several task. you can do as this code below.

AsyncTaskHelper().let {
            it.execute(Callable {
                // task 1 do in background
                null
            },Callable{
                // task 2 do in background
                null
            },Callable{
                // task 3 do in background
                null
            })

            it.taskListener = object : AsyncListener {
                override fun onFinished(obj: Any) {
                    // when task1,task2,task3 has been finished . it will do in this area
                }

            }
        }