Why we need declare parcelable object in AIDL file?
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If we have a class that would like to send from one process to another through an IPC interface, we have to create a class that support parcelable protocol (implements Parcelable).

**In addition, we have to create an .aidl file which declares that parcelable class.
Since this .aidl file will not generate a .java file as usual,I wonder the reason why we need to do it.**
