Serialize and De-serialize PublisherInterstitialAd object - serialization

Question

Is it possible to serialize and de-serialize PublisherInterstitialAd object of Google DFP ads, so as to save and retrieve the object in SharedPreferences?
When I tried doing using Gson library, I got StackOverflowError. Please do suggest how best this can be done and where I would be going wrong in my current approach.
Thank you.
These are the methods am using for saving and retrieving the Ad object in SharedPreferences, where publisherInterstitialAd is the object in question.
public void saveInterstitialAd(PublisherInterstitialAd publisherInterstitialAd) {
Gson gson = new Gson();
String json = gson.toJson(publisherInterstitialAd);
mEditor.putString("InterstitialAd", json);
mEditor.commit();
}
public PublisherInterstitialAd getInterstitialAd(){
Gson gson = new Gson();
String json = mSharedPrefs.getString("InterstitialAd", "");
if(json.equals(""))
return null;
return gson.fromJson(json, PublisherInterstitialAd.class);
}
and this is the stack trace am getting:
UncaughtException
java.lang.StackOverflowError
at java.lang.Class.isArray(Class.java:1118)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:96)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:551)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:544)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:551)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:544)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:551)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:544)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:551)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:544)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:551)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:544)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:551)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:544)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:551)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:544)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:551)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:544)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:551)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:544)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:551)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:544)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:551)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:544)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:551)
at com.google.gson.internal.$Gson$Types.canonicalize($Gson$Types.java:109)
at com.google.gson.internal.$Gson$Types$WildcardTypeImpl.($Gson$Types.java:544)
at com.google.gson.internal.$Gson$Types.canonical

Answer 1

I think Google would argue that you shouldn't store ads long-term. They must be aware that their Ad objects aren't serializable or Parcelable, so that leads me to believe it is intentional.
That having been said, if you really must, you can always store the objects on your Application object (I really recommend against this, though, as that is a serious anti-pattern full of pitfalls). I'd recommend instead just asking for the interstitial in any activity that you might ultimately show it in (if, for example, your goal is to show an interstitial after an Activity is complete, maybe load the interstitial when the Activity is first created, then show it before you finish the activity, after the user has committed whatever action you wanted them to).