HandlerReferenceActivity.kt

package com.codehangouts.sampleapp.memoryleak.kotlin.thread.handlers

import android.os.Bundle
import android.os.Handler
import android.os.Message
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity

import com.example.myapplication.R

import java.lang.ref.WeakReference

class HandlerReferenceActivity : AppCompatActivity() {

    private val title: TextView? = null

    private val innerHandler = InnerHandler(this)

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        /*
         * Commented lines is responsible for memory leaks as it holds implicit
         *  reference of Activity.
         * */
        /*new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                title.setText(getString(R.string.title_dashboard));
            }
        }, 2000);*/
        /*
           Instead create static class for handler and runnable both.
         */
        innerHandler.postDelayed(handlerRunnable, 2000)
    }

    private class InnerHandler(activity: HandlerReferenceActivity) : Handler() {
        /*
         * Fix for reference - Use weak reference instead of directly holding
         * the activity reference.
         * */
        private val weakReferenceActivity: WeakReference<HandlerReferenceActivity>

        init {
            weakReferenceActivity = WeakReference(activity)
        }

        override fun handleMessage(msg: Message) {
            val activity = weakReferenceActivity.get()
            if (activity != null) {
                activity.title!!.text = activity.getString(R.string.title_dashboard)
            }
        }
    }

    companion object {

        private val handlerRunnable = Runnable { /* ... */ }
    }
}