BundleDeserializationCast

When a Serializable object is placed in an android.os.Bundle, certain types whose serialization is handled with custom logic are 'flattened' to their base types. Casting items retrieved from a bundle with bundle.getSerializable(...) back to their original types may therefore cause a ClassCastException.

See discussion here.

Casting the result of bundle.getSerializable(...) to any subtype of any of the following classes is forbidden¹:

• Map (except HashMap)
• List (except ArrayList or any Parcelable)
• SparseArray (except Parcelables)
• CharSequence (except String or any Parcelable)
• CharSequence[] (except String[])

Note that getSerializable happens to return HashMaps for any Map implementation or ArrayLists for any List implementation, however, this is not guaranteed by the API. Therefore, casting to ArrayList or HashMap is allowed, but it is safer to cast to the base List or Map.

An exception is made for most types if they also implement Parcelable, as they are handled such that their type is preserved.

In many cases, you may be able to cast your object to its base type without any ill effects if you don't require any features of a specific implementation.

In other cases, there may be an constructor that will create an instance of your type from an instance of the base type (but beware of null results causing IllegalArgumentExceptions!) For example:

TreeMap<K, V> myMap;
Map<K, V> deserialized = (Map<K, V>) myBundle.getSerializable("KEY");
myMap = deserialized == null ? null : new TreeMap<K, V>(deserialized);

If you really need a different workaround, wrapping your object (e.g. of type MyList) in an arbitrary wrapper class (e.g. MyListHolder) that implements just Serializable will serialize and deserialize it through the standard Serializable path and preserve your original type.