Framework层：

    @Override

    public StackInfo getStackInfo(int stackId) {

        final int callingUid = Binder.getCallingUid();　// 拿到调用者身份

        if (callingUid != 0 && callingUid != Process.SYSTEM_UID) {

            // TODO

        }

        long ident = Binder.clearCallingIdentity(); // 转调用身份为android

        try {

            // TODO

        } finally {

            Binder.restoreCallingIdentity(ident);// 做完事之后，恢复调用者身份

        }

    }