Unit defined in com.unity3d.ads.IUnityAdsInitializationListener

Question

Class 'MainActivity' is not abstract and does not implement abstract member public abstract fun onInitializationComplete(): Unit defined in com.unity3d.ads.IUnityAdsInitializationListener

class MainActivity : AppCompatActivity(), IUnityAdsInitializationListener {

private lateinit var webView: WebView
private lateinit var passwordLayout: TextInputLayout
private lateinit var passwordEditText: TextInputEditText
private lateinit var buttonLogin: Button
private lateinit var swipeRefreshLayout: SwipeRefreshLayout
private var isAtTop = true
private lateinit var passwordList: List<String>

private val unityGameID = "1234567"
private val testMode = true
private val adUnitId = "rewardedVideo"

private val loadListener = object : IUnityAdsLoadListener {
    override fun onUnityAdsAdLoaded(placementId: String) {
        UnityAds.show(this@MainActivity, adUnitId, UnityAdsShowOptions(), showListener)
    }

    override fun onUnityAdsFailedToLoad(placementId: String, error: UnityAdsLoadError, message: String) {
        Log.e("UnityAdsExample", "Unity Ads failed to load ad for $placementId with error: [$error] $message")
    }
}

private val showListener = object : IUnityAdsShowListener {
    override fun onUnityAdsShowFailure(placementId: String, error: UnityAdsShowError, message: String) {
        Log.e("UnityAdsExample", "Unity Ads failed to show ad for $placementId with error: [$error] $message")
    }

    override fun onUnityAdsShowStart(placementId: String) {
        Log.v("UnityAdsExample", "onUnityAdsShowStart: $placementId")
    }

    override fun onUnityAdsShowClick(placementId: String) {
        Log.v("UnityAdsExample", "onUnityAdsShowClick: $placementId")
    }

    override fun onUnityAdsShowComplete(placementId: String, state: UnityAdsShowCompletionState) {
        Log.v("UnityAdsExample", "onUnityAdsShowComplete: $placementId")
        if (state == UnityAdsShowCompletionState.COMPLETED) {
            // Reward the user for watching the ad to completion
            // Implement your reward logic here
        } else {
            // Do not reward the user for skipping the ad
        }
    }
}