AdMob Rewarded Ad Implementation in Android Studio (Kotlin) – Step-by-Step Guide

1. What are AdMob Rewarded Ads?

Image by: iion

AdMob rewarded ads let users watch a full-screen video (or interactive ad) in exchange for a reward:

• Unlock a premium feature

• Enable “Pro” settings (like volume-button scrolling)

• Give in-app coins, hints, or extra lives

They’re perfect for non-intrusive monetization: user chooses to watch the ad instead of you forcing it.

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2. Prerequisites

• Android Studio installed

• A project using Kotlin

• Google Mobile Ads SDK added

• Your AdMob App ID and Rewarded Ad Unit ID (use test IDs during development)

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3. Add the Google Mobile Ads SDK

3.1. Add Gradle dependency

In your app-level build.gradle:

dependencies {
    implementation("com.google.android.gms:play-services-ads:24.8.0") // or latest
}

Sync the project.

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4. Add AdMob App ID in AndroidManifest.xml

Inside <application> tag:

<meta-data
    android:name="com.google.android.gms.ads.APPLICATION_ID"
    android:value="@string/admob_app_id" />

And in res/values/strings.xml:

<!-- AdMob Test IDs -->
<string name="admob_app_id">ca-app-pub-3940256099942544~3347511713</string>
<string name="admob_banner_ad_unit_id">ca-app-pub-3940256099942544/6300978111</string>
<string name="admob_native_ad_unit_id">ca-app-pub-3940256099942544/2247696110</string>
<string name="admob_interstitial_ad_unit_id">ca-app-pub-3940256099942544/1033173712</string>
<string name="admob_rewarded_ad_unit_id">ca-app-pub-3940256099942544/5224354917</string>
<string name="admob_app_open_ad_unit_id">ca-app-pub-3940256099942544/9257395921</string>

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5. Initialize Mobile Ads (Usually in Application or first Activity)

In onCreate() of your Application class or main Activity, once in app:

MobileAds.initialize(this) {}

If you don’t have a custom Application class, you can initialize in your main activity’s onCreate() once.

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6. Basic Rewarded Ad Flow (Concept)

• Load rewarded ad → loadRewardedAd()

• Show dialog → “Watch Ad to Unlock Feature”

• Show ad → rewardedAd.show()

• On reward callback → enable your feature

• Reload a new rewarded ad for next time

We’ll implement this pattern now.

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7. Implement Rewarded Ad in Kotlin

• Initialize at top of onCreate

private var rewardedAd: RewardedAd? = null

• Call it inside onCreate/onViewCreated

loadRewardedAd()

• Create functions

// Load Rewarded Ad
private fun loadRewardedAd() {
    val adRequest = AdRequest.Builder().build()

    RewardedAd.load(
        requireContext(),
        getString(R.string.admob_rewarded_ad_unit_id),
        adRequest,
        object : RewardedAdLoadCallback() {
            override fun onAdLoaded(ad: RewardedAd) {
                rewardedAd = ad
            }

            override fun onAdFailedToLoad(error: LoadAdError) {
                rewardedAd = null
            }
        }
    )
}
// Unlock with Ad dialog
private fun showPremiumFeatureDialog(onRewardEarned: () -> Unit) {
    MaterialAlertDialogBuilder(requireContext())
        .setTitle("Unlock Premium Feature")
        .setMessage("Watch a short ad to delete this comic")
        .setPositiveButton("  Watch Ad  ") { _, _ ->
            showLoadingAndRewardedAd(onRewardEarned)
        }
        .setNegativeButton("No Thanks", null)
        .show()
        .apply {
            getButton(AlertDialog.BUTTON_POSITIVE)?.apply {
                backgroundTintList = ColorStateList.valueOf(
                    ContextCompat.getColor(requireContext(), R.color.primary)
                )
                setTextColor(Color.WHITE)
            }
        }
}
// Show Rewarded Ad
private fun showLoadingAndRewardedAd(onRewardEarned: () -> Unit) {
    val loadingDialog = MaterialAlertDialogBuilder(requireContext())
        .setTitle("Loading Ad")
        .setMessage("Please wait...")
        .setCancelable(false)
        .create()

    loadingDialog.show()

    val ad = rewardedAd
    if (ad != null) {
        ad.fullScreenContentCallback = object : FullScreenContentCallback() {
            override fun onAdDismissedFullScreenContent() {
                loadingDialog.dismiss()
                rewardedAd = null
                loadRewardedAd() // reload for next time
            }

            override fun onAdFailedToShowFullScreenContent(error: AdError) {
                loadingDialog.dismiss()
                rewardedAd = null
            }
        }

        ad.show(requireActivity()) { _ ->
            loadingDialog.dismiss()
            onRewardEarned()
        }
    } else {
        loadingDialog.dismiss()
        MaterialAlertDialogBuilder(requireContext())
            .setTitle("Ad Not Ready")
            .setMessage("Please try again in a moment")
            .setPositiveButton("OK", null)
            .show()
    }
}

Note: for Activity change requireContext() to this@yourActivity or this

• Call showPremiumFeatureDialog() in Action

binding.btnAction.setOnClickListener {
    showPremiumFeatureDialog{
        // Reward Generated(Next Action)
    }
}

8. Imports

import com.google.android.gms.ads.AdRequest
import com.google.android.gms.ads.AdError
import com.google.android.gms.ads.FullScreenContentCallback
import com.google.android.gms.ads.LoadAdError
import com.google.android.gms.ads.rewarded.RewardedAd
import com.google.android.gms.ads.rewarded.RewardedAdLoadCallback

AdMob Rewarded Ad Implementation done.