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Editorial Team
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Asked: 2026-06-07T09:32:37+00:00

I am working with the android NDK trying to use an existing library to

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I am working with the android NDK trying to use an existing library to build an Application.

The following function is declared in the library…

BYTE __stdcall InitRelay(fp_setbaud _setbaud, fp_get _get, fp_put _put, fp_flush _flush, fp_delay _delay){

These are the declarations for the parameters passed to InitRelay…

typedef void (__stdcall *fp_setbaud)(WORD);
typedef short (__stdcall *fp_get)(WORD);
typedef void (__stdcall *fp_put)(BYTE);
typedef void (__stdcall *fp_flush)(void);
typedef void (__stdcall *fp_delay)(WORD);
 typedef short (__stdcall *fp_ProgressUpdate)(WORD);

I’ve been to this thread, but still am not sure what to do. The difference between what I am doing and what they are doing, is that I want to call a native function in C that requires a function pointer as a parameter.

I was considering writing a wrapper function in the Native code, does that sound right? My main problem is that I cannot change the native code i’ve been given, but I can add new functions. I know people will ask me to post my java code, so I will, but it is literally useless. It is just a method call with parameters that currently don’t make sense to java. 

 // InitRelay
    InitRelay( fp_setbaud _setbaud, fp_get _get, fp_put, fp_flush _flush, fp_delay _delay );
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1 Answer

  1. Editorial Team

    Yes, write native wrappers. You will need to do this anyway as jni has very particular naming requirements for the interface functions. Non-trivial data types will also require copy conversion from/to jni references.

    Process-level static state in the library can also give you a lot of headaches, since android does not link the lifetime of a process to a user perceptible session lifetime. Android will also quite happily put multiple distinct sessions into the same process.

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