InnerAsyncTaskReferenceActivity.kt

package com.codehangouts.sampleapp.memoryleak.kotlin.innerasynctask

import android.os.AsyncTask
import android.os.Bundle
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity

import com.example.myapplication.R

import java.lang.ref.WeakReference

class InnerAsyncTaskReferenceActivity : AppCompatActivity() {

    /*
     * Following mistakes should be avoided in this scenario.
     * Mistake  1. Try to avoid referencing a class inside an activity because normal inner class holds implicit reference of parent class.
     * If at we need to do it,make it private static class which does not hold any implicit reference.
     * Mistake  2. Never use a direct reference of a view, reference of Activity itself or context from activity inside an Asynctask.
     * Mistake 3. Specially in case of AsycTask Inner class : We should always cancel the asyncTask inside onDestroy of  Activity because the asyncTask will still be running even if the activity
     * is destroyed preventing activity to be garbage collected.
     *
     * */
    private val textView: TextView? = null
    private var backgroundOperation: BackgroundOperation? = null

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)
        setContentView(R.layout.inner_async_task_activity)

        /*
         * Initiate & execute AsyncTask here!
         * */
        backgroundOperation = BackgroundOperation(textView)
        backgroundOperation!!.execute()
    }


    private inner class BackgroundOperation internal constructor(textView: TextView) : AsyncTask<Void, Void, String>() {

        //private View view;
        private val viewWeakReference: WeakReference<TextView>

        init {
            //this.view = view; // Problem 2
            // Instead use WeakReference
            this.viewWeakReference = WeakReference(textView)
        }

        override fun doInBackground(vararg voids: Void): String {

            try {
                Thread.sleep(5000)
            } catch (e: InterruptedException) {
                e.printStackTrace()
            }

            return "The task is completed!"
        }

        override fun onPostExecute(value: String) {
            super.onPostExecute(value)
            //textView.setText(s);
            val view = viewWeakReference.get()
            if (view != null) {
                view.text = value
            }
        }
    }

    override fun onDestroy() {
        super.onDestroy()
        /*
         * Always cancel AsyncTask when activity is destroyed.
         */
        if (backgroundOperation != null) {
            backgroundOperation!!.cancel(true)
        }
    }
}