When reading an object from a parcel in Android, when we not want to use the default ClassLoader?

Question

When implementing the Parcelable interface, the CREATOR implementation typically uses a constructor that takes in a Parcel e.g.

public Foo(Parcel parcel)

In this parcel, we might have code like

mMyField = parcel.readParcelable(MyFoo.class.getClassLoader())

As far as I can tell, it's usually ok to just use the default class loader and pass in null instead since parcel.writeParcelable(mMyField) already stores the class name in the parcel.

So my question is, when would I need to use MyFoo.class.getClassLoader() instead of passing in null?

Answer 1

Since a Parcel stores info about its class, but not the class itself, that class will be loaded from a name, like java/util/ArrayList. If your class is nt on the classpath or the .class file is on a remote server even you will need to use a different ClassLoader that can access it, for example URLClassLoader.