Creating a background application using NDK ( C code only )

[Raj]

    New to Android development & to NDK, Need help in creating background helper application's using NDK. I have to port a large application in C to Android platform and my main C application makes use of few standalone applications which run in the background (as services on windows & as daemons on Linux). So how can I create these standalone applications in Andriod platform. I'm aware that these have to be services in Android applications, but the services are written using Java code & NDK doesn't support services & all my application code is in C. So how can I port these standalone applications onto Android along with my main application which uses these standalone helper applications. Should they be made separate libraries ? I'm not sure, so any pointers will be very helpful. Please Note: Rooting the device is not allowed.

[Damien Cooke]

You will need to write entry functions in C using JNI to allow them to be called from Java.  Even the services you need to run should be ok (I have never written a service containing JNI ) as you should just call your entry functions from:

@Override

public int onStartCommand(Intent intent, int flags, int startId) 

{

.......

}

I would start with one of the services and essentially write a C routine that starts the daemon using JNI exports.  Then import that and execute it in the above Service callback method.  Make sure you clean up by creating a JNI C method to clean up the C library and call it in 

@Override

public void onTaskRemoved(Intent rootIntent)

{

.........

}

it is a big job you have been handed, I can give you some sample methods etc if you get back to me to help you get going.

Damien

On Thu, Aug 9, 2018 at 2:25 AM Raj <rajash...@gmail.com> wrote:

    New to Android development & to NDK, Need help in creating background helper application's using NDK. I have to port a large application in C to Android platform and my main C application makes use of few standalone applications which run in the background (as services on windows & as daemons on Linux). So how can I create these standalone applications in Andriod platform. I'm aware that these have to be services in Android applications, but the services are written using Java code & NDK doesn't support services & all my application code is in C. So how can I port these standalone applications onto Android along with my main application which uses these standalone helper applications. Should they be made separate libraries ? I'm not sure, so any pointers will be very helpful. Please Note: Rooting the device is not allowed.

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[Raj Shekar]

Hi Damien,

    Thanks for your time & reply, your help would definitely help me in getting the project up & running. Currently, I have the NDK set up and have a sample application which uses JNI and native code. I have the main activity which uses JNI. The methods onStartCommand( ... ) & onTaskRemoved( ... ) are used to create the services & when the service is stopped respectively, should I be creating the services in the main activity or where ? May be I'm asking too basic questions, but I want to be sure that it's the right way to do it.

Can you please help me in understanding - 'write a C routine that starts the daemon using JNI exports. Then import that and execute it in the above Service callback method.  Make sure you clean up by creating a JNI C method to clean up the C library and call it in onTaskRemoved( ... ) method '. (sorry that I didn't get exactly the meaning).

And finally, it would be very helpful if I can get some example on either Github or in some other repository. It would be really helpful.

Thanks for your time again.

Thanks,

Raj.

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