AIDL 编译报can be an out parameter, so you must declare it as in, out or inout原因探究

最新推荐文章于 2024-12-24 15:47:54 发布

原创最新推荐文章于 2024-12-24 15:47:54 发布 · 9.4k 阅读

3 ·

CC 4.0 BY-SA版权

文章标签：

#parameters #server #output #input #interface #google

Android 专栏收录该内容

11 篇文章

订阅专栏

在AIDL中遇到错误提示'parameter can be an out parameter, so you must declare it as in, out or inout'。文章通过一个问题及解答解释了AIDL与Java的区别，强调了AIDL中参数的方向性——in, out, inout，用于确定对象在客户端到服务器之间传递时数据的复制。明确参数类型可以避免此类错误：in表示输入，out表示输出，inout表示输入输出。" 125572541,11480998,CTF挑战：利用easy_eval进行代码执行,"['网络安全', 'PHP安全', '代码执行', 'CTF挑战', '漏洞利用']

从Google Group上copy下面这个问题及其回答，它解释了其中的原因。

问题：

Gavin Bong wrote:

I'm getting this error when running "ant aidl".

/data/projects2008/android/iteration1/lib/src/org/android/ common/IAdUnitAvailability.aidl:5 parameter 1: 'Advert ad' can be an out parameter, so you must declare it as in, out or inout.

IAdUnitAvailability.aidl

I have an interface method with signature:

void gimmeAds( Advert ad );

What am I missing ?

回答如下：

AIDL isn't Java. It's real close, but it's not Java.

One thing AIDL has that Java doesn't is the notion of "direction" for parameters, which determine what data needs to be copied "on the wire" as objects get passed from the client to the server and back again.

If the Advert ad parameter is purely input -- meaning it's data passed from client to server -- you need to declare it in the AIDL as:

void gimmeAds(in Advert ad);

If the Advert ad parameter is purely output -- meaning it's data is passed from server to client -- use:

void gimmeAds(out Advert ad);

If the Advert ad is both input and output -- the client provides a value, and the server might modify it in ways the client needs to see -- use:

void gimmeAds(inout Advert ad);

This is only needed for non-primitive parameters to AIDL methods. So if the ad parameter were a float instead of an Advert, you wouldn't have received the error.