来自本机代码的NDK调用函数

Question

I am trying to call a simple connection function from native C code using the NDK and JNI. The following is my code:

C code - returns a value

freerdp_ext_connect(const char *host, const char *username,
                    const char *pass, const char *domain,
                    int width, int height){}

Java code:

#include <jni.h>
#include <stdio.h>
#include <freerdp/freerdp.h>

jstring Java_com_example_freerdpandroid_FreeRDPActivity_test(JNIEnv* env, jobject javaThis)
{

 freerdp_ext_connect("10.123.123.12", "admin", "dsadsad", "", 600, 800);

    return (*env)->NewStringUTF(env, "dsfsdf");

}

When trying to compile with cygwin it's giving me this error:

./obj/local/armeabi/objs/freerdp/freerdp.o: In function `Java_com_example_freerdpandroid_FreeRDPActivity_test':
C:\Users\stefan.scerri\workspace\freerdp/jni/freerdp.c:11: undefined reference to `freerdp_ext_connect'
collect2: ld returned 1 exit status
/cygdrive/c/android-ndk/android-ndk/build/core/build-binary.mk:378: recipe for target `obj/local/armeabi/libfreerdp.so' failed
make: *** [obj/local/armeabi/libfreerdp.so] Error 1

Any idea why this is so? I believe it is because of the return value of the C function, however I'm not sure, can someone kindly confirm. Thanks in advance.

Answer 1

Is the freerdp_ext_connect in a compiled library, by any chance? If so, are you linking to that library when you build your NDK project? To link with a library, place the following into Android.mk:

LOCAL_LDLIBS := -lfoo

And the linker will link against libfoo.a or libfoo.so, whichever is available.

If freerdp_ext_connect is in a source file - are you compiling that source file? The source file must be listed under LOCAL_SRC_FILES in Android.mk.