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POJNI loses reference to native methods
 

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    <p>As an example for later use in Android I wrote a simple callback interface. While doing so i ran into the following error or bug or whatever. In C the two commented lines are supposed to be executed resulting in calling the C callback onChange. But instead i get an UnsatisfiedLinkError. Calling the native Method directly in Java works just fine. Calling it directly from C as presented here in the example also produces the UnsatisfiedLinkError. I'm open for any advice concerning this issue or work arounds and so on. The Java Part:</p> <pre><code>import java.util.LinkedList; import java.util.Random; interface Listener { public void onChange(float f); } class Provider { LinkedList&lt;Listener&gt; all; public Provider() { all = new LinkedList&lt;Listener&gt;(); } public void registerChange(Listener lst) { all.add(lst); } public void sendMsg() { Random rnd = new Random(); for(Listener l : all) { try { l.onChange(rnd.nextFloat()); } catch(Exception e) { System.out.println(e); } } } } class Inheritance implements Listener { static public void main(String[] args) { System.load(System.getProperty("user.dir") + "/libinheritance.so"); } public native void onChange(float f); } </code></pre> <p>The C Part:</p> <pre><code>#include "inheritance.h" jint JNI_OnLoad(JavaVM *jvm, void *reserved) { JNIEnv *env; (*jvm)-&gt;GetEnv(jvm, (void**)&amp;env, JNI_VERSION_1_4); jclass inheritance = (*env)-&gt;FindClass(env, "Inheritance"); jobject o_inheritance = (*env)-&gt;NewObject(env, inheritance, (*env)-&gt;GetMethodID(env, inheritance, "&lt;init&gt;", "()V")); jclass provider = (*env)-&gt;FindClass(env, "Provider"); jobject o_provider = (*env)-&gt;NewObject(env, provider, (*env)-&gt;GetMethodID(env, provider, "&lt;init&gt;", "()V")); g_inheritance = (*env)-&gt;NewGlobalRef(env, inheritance); g_provider = (*env)-&gt;NewGlobalRef(env, provider); (*env)-&gt;CallVoidMethod(env, o_inheritance, (*env)-&gt;GetMethodID(env, inheritance, "onChange", "(F)V"), 1.0); //(*env)-&gt;CallVoidMethod(env, o_provider, (*env)-&gt;GetMethodID(env, provider, "registerChange", "(LListener;)V"), o_inheritance); //(*env)-&gt;CallVoidMethod(env, o_provider, (*env)-&gt;GetMethodID(env, provider, "sendMsg", "()V")); (*env)-&gt;DeleteLocalRef(env, o_inheritance); (*env)-&gt;DeleteLocalRef(env, o_provider); return JNI_VERSION_1_4; } JNIEXPORT void JNICALL JNI_OnUnload(JavaVM *jvm, void *reserved) { JNIEnv *env; (*jvm)-&gt;GetEnv(jvm, (void**)&amp;env, JNI_VERSION_1_4); (*env)-&gt;DeleteGlobalRef(env, g_inheritance); (*env)-&gt;DeleteGlobalRef(env, g_provider); } JNIEXPORT void JNICALL Java_Inheritance_onChange(JNIEnv *env, jobject self, jfloat f) { printf("[C] %f\n", f); } </code></pre> <p>The header file:</p> <pre><code>#include &lt;jni.h&gt; /* Header for class Inheritance */ #ifndef _Included_Inheritance #define _Included_Inheritance #ifdef __cplusplus extern "C" { #endif jclass g_inheritance, g_provider; /* * Class: Inheritance * Method: onChange * Signature: (F)V */ JNIEXPORT void JNICALL Java_Inheritance_onChange(JNIEnv *, jobject, jfloat); jint JNI_OnLoad(JavaVM *, void *); #ifdef __cplusplus } #endif #endif </code></pre> <p>Compilation:</p> <pre><code>gcc -c -fPIC -I /usr/lib/jvm/java-6-openjdk/include -I /usr/lib/jvm/java-6-openjdk/include/linux/inheritance.c inheritance.h gcc -g -o -shared libinheritance.so -shared -Wl,-soname,libinheritance.so -lc inheritance.o </code></pre>
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