On Exit button press how to show Rewarded Video Ads

After buy from codecanyon I configure the app and everything was fine. Now I wast to show Rewarded ads when use click on the exit button.

Add the below line of code to add this function.

override fun onBackPressed() {
    if (mBinding.drawerLayout.isDrawerOpen(GravityCompat.START)) run {
    mBinding.drawerLayout.closeDrawer(GravityCompat.START)
} else if (mBinding.drawerLayout.isDrawerOpen(GravityCompat.END)) run {
    mBinding.drawerLayout.closeDrawer(GravityCompat.END)
} else if (mBinding.webView.canGoBack()) {
    mBinding.webView.goBack()
} else {
    if (isDoubleBackToExit) {
        super.onBackPressed()
    }

    try {
        if(mRewardedVideoAd != null){
            if(isApplicationAlive)
                mRewardedVideoAd!!.show(this@HomeActivity) {
                    fun onUserEarnedReward(rewardItem: RewardItem) {
                        val rewardAmount = rewardItem.amount
                        val rewardType = rewardItem.type
                        Log.d(TAG, "Reward type: $rewardType")
                        Log.d(TAG, "Reward amount: $rewardAmount")
                    }
                }
        }
    }catch (ex: java.lang.Exception){
        ex.printStackTrace()
    }

    isDoubleBackToExit = true
    UtilMethods.showSnackbar(mBinding.rootContainer, getString(R.string.massage_exit))

    Handler().postDelayed({ run {
        isDoubleBackToExit = false
    }
    }, 2000)

  }
}