PL286/system/tools/aidl/docs/constants.md

Defining constants as part of an interface

AIDL has been enhanced to support defining integer and string constants as part of an interface.

Integer constants

interface IMyInterface {
    const int CONST_A = 1;
    const int CONST_B = 2;
    const int CONST_C = 3;
    ...
}

These map to appropriate 32 bit integer class constants in Java and C++ (e.g. IMyInterface.CONST_A and IMyInterface::CONST_A respectively).

String constants

interface IMyInterface {
    const String CONST_A = "foo";
    const String CONST_B = "bar";
    ...
}

These map to class level String constants in Java, and static getter functions that return a const android::String16& in C++.

The constants are limited to contain printable ASCII characters < 0x10 and without backspaces (i.e. no '' character).