Admob非页内广告仅在应用中显示一次

Question

我正在设计一款应用，用户点击按钮即可显示插页式广告。 关闭广告后，计数器会添加到一个广告，然后显示。 基本上，它是通知用户他们观看了多少广告。 但是计数器没有添加，广告也没有更新。 这是代码： -

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import com.google.android.gms.ads.AdListener;
import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.InterstitialAd;
import com.google.android.gms.ads.MobileAds;

public class MainActivity extends AppCompatActivity {

private InterstitialAd mInterstitialAd;
private Button watchButton;
int count=0;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    //TextView tv_data=(TextView)findViewById(R.id.disCount);
    MobileAds.initialize(this,
            "ca-app-pub-3940256099942544~3347511713");

    mInterstitialAd = new InterstitialAd(this);
    mInterstitialAd.setAdUnitId("ca-app-pub-3940256099942544/1033173712");
    mInterstitialAd.loadAd(new AdRequest.Builder().build());
    mInterstitialAd.setAdListener(new AdListener() {
        @Override
        public void onAdClosed() {
            mInterstitialAd.loadAd(new AdRequest.Builder().build());
            count++;
            TextView tv_data=findViewById(R.id.disCount);
            setContentView(R.layout.activity_main);
            tv_data.setText(Integer.toString(count));
            // Load the next interstitial.

        }

    });
    watchButton = findViewById(R.id.button_send);
    watchButton.setOnClickListener(new View.OnClickListener() {
        // Listen for when user presses button
        public void onClick(View v) {
            // If a interstitial is ready, show it
            if(mInterstitialAd.isLoaded()) {
                mInterstitialAd.show();

            }
            else
            {
                mInterstitialAd.loadAd(new AdRequest.Builder().build());
            }
            // Otherwise end this activity (go back to first activity)
        }
    });
}
}