How to start Second Activity when ad is closed? (Kotlin)

Question

In my app, the user starts in the MainActivity. When the button (btn) is clicked, an interstitial ad pops up. I want it to go to the SecondActivity when the ad is closed, but it just goes back to MainActivity. I've pasted my code below

class MainActivity : AppCompatActivity() {
private var mInterstitialAd: InterstitialAd? = null
val i:Intent = Intent(this, SecoundActivity::class.java)


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

    MobileAds.initialize(this) {}
    var adRequest = AdRequest.Builder().build()

    InterstitialAd.load(this, "ca-app-pub-3940256099942544/1033173712", adRequest, object : InterstitialAdLoadCallback() {
        override fun onAdFailedToLoad(adError: LoadAdError) {
            mInterstitialAd = null
        }

        override fun onAdLoaded(interstitialAd: InterstitialAd) {

            mInterstitialAd?.fullScreenContentCallback = object:FullScreenContentCallback() {
                override fun onAdDismissedFullScreenContent() {
                    startActivity(i)
                }
            }
            mInterstitialAd = interstitialAd
        }
    })

    btn.setOnClickListener {
        if (mInterstitialAd != null) {
            mInterstitialAd?.show(this)

        }
    }
}

}

Any way to solve this. Thanks

Answer 1

Since your mInterstitialAd is nullable, your FullScreenContentCallback is never going to be initialized, because mInterstitialAd is null when you're trying to invoke it. It will be executed before onAdLoaded will be called.

Put the full screen content callback in the onAdLoaded callback like this

    override fun onAdLoaded(interstitialAd: InterstitialAd) {
        interstitialAd.fullScreenContentCallback = object:FullScreenContentCallback() {
            override fun onAdDismissedFullScreenContent() {
                startActivity(i)
            }
        }
        mInterstitialAd = interstitialAd  
    }
 

Also it is best practice to put variable initialization to the top of the class instead of the bottom

private var mInterstitialAd: InterstitialAd? = null
private val i = Intent(this, SecondActivity::class.java)