title: show Interstitial Ad on back button pressed?
body: <p><strong>This is my manifest file:</strong></p>
  
  <pre><code>&lt;activity
          android:screenOrientation="portrait"
          android:name="com.google.android.gms.ads.AdActivity"
          android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize"
          android:theme="@android:style/Theme.Translucent" /&gt;
  </code></pre>
  
  <p><strong>This is my activity:</strong></p>
  
  <pre><code> @Override
  public void onBackPressed() {
      InterstitialAd interstitialAd= new InterstitialAd(this);
      interstitialAd.setAdUnitId(getString(R.string.interstitial_full_screen));
      AdRequest adRequest = new AdRequest.Builder().build();
      interstitialAd.loadAd(adRequest);
  
      interstitialAd.setAdListener(new AdListener() {
          @Override
          public void onAdLoaded() {
  
              if (interstitialAd.isLoaded()) {
                  interstitialAd.show();
              }
  
          }
  
          @Override
          public void onAdClosed() {
              super.onAdClosed();
              finish();
  
          }
      });
  
  }
  </code></pre>
  
  <p>I am getting an ad screen only 2-3 times while pressing the back button.So,how can I solve it, on every back button press.</p>