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POHow does JNIEnv global referencing differ from jobject in C?
 

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  1. POHow does JNIEnv global referencing differ from jobject in C?
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    <p>I have my JNI environment and jobject objects saved locally as of now. I found that for my JNI to run of ICS and up devices, I need to fix my JNI code. This is the error I get:</p> <pre><code>02-20 10:20:59.523: E/dalvikvm(21629): JNI ERROR (app bug): attempt to use stale local reference 0x38100019 02-20 10:20:59.523: E/dalvikvm(21629): VM aborting 02-20 10:20:59.523: A/libc(21629): Fatal signal 11 (SIGSEGV) at 0xdeadd00d (code=1), thread 21629 </code></pre> <p>I am confused about how to create/destroy these globals, and if I am even doing it right.</p> <p>My application currently runs fine on all pre-ICS devices using this code:</p> <pre><code>BYTE Java_my_eti_commander_RelayAPIModel_00024NativeCalls_InitRelayJava( JNIEnv *env, jobject obj ) { myEnv = (env); myObject = obj; changeID = (*myEnv)-&gt;GetStaticMethodID( myEnv, myObject, "changeItJavaWrapper", "(S)V" ); getID = (*myEnv)-&gt;GetStaticMethodID( myEnv, myObject, "getItJavaWrapper" , "(S)S" ); putID = (*myEnv)-&gt;GetStaticMethodID( myEnv, myObject, "putItJavaWrapper" , "(B)V" ); flushID = (*myEnv)-&gt;GetStaticMethodID( myEnv, myObject, "flushItJavaWrapper" , "()V" ); delayID = (*myEnv)-&gt;GetStaticMethodID( myEnv, myObject, "delayItJavaWrapper" , "(S)V" ); RelayAPI_SetBaud= WrapSetBaud; RelayAPI_get = WrapGetIt; RelayAPI_put = WrapPutIt; RelayAPI_flush = WrapFlushIt; RelayAPI_delay = WrapDelayIt; ... } </code></pre> <p>Under the <code>GetStaticMethodID</code> calls, the RelayAPI_ variables are all function pointers that lead here:</p> <pre><code>void WrapSetBaud( WORD w ) { return (*myEnv)-&gt;CallStaticVoidMethod( myEnv, myObject, changeID, w ); } short WrapGetIt( WORD time ) { return (*myEnv)-&gt;CallStaticShortMethod( myEnv, myObject, getID, time ); } void WrapPutIt( BYTE buff ) { return (*myEnv)-&gt;CallStaticVoidMethod( myEnv, myObject, putID, buff ); } void WrapFlushIt( void ) { return (*myEnv)-&gt;CallStaticVoidMethod( myEnv, myObject, flushID ); } void WrapDelayIt( WORD wait ) { return (*myEnv)-&gt;CallStaticVoidMethod( myEnv, myObject, delayID, wait ); } </code></pre> <p>Finally, it returns to my Java code here:</p> <pre><code>public static void changeItJavaWrapper( short l ) throws IOException { mModelService.changeitJava( l ); } public static void flushItJavaWrapper() { mModelService.flushitJava(); } public static void putItJavaWrapper( byte p ) { mModelService.putitJava( p ); } public static void delayItJavaWrapper( short wait ) { mModelService.delayitJava( wait ); } public static short getItJavaWrapper( short s ) throws IOException { return mModelService.getitJava( s ); } </code></pre> <p>I have changed my initializations to:</p> <pre><code>myEnv = (*env)-&gt;NewGlobalRef(env,obj); myObject = (*env)-&gt;NewGlobalRef(env,obj); </code></pre> <p>But i'm extremely confused with this, as they have the same parameters, and it just doesn't make sense. I can't find documentation for this method anywhere as stupid as that sounds, <a href="http://android-developers.blogspot.com/2011/11/jni-local-reference-changes-in-ics.html" rel="nofollow"><code>this tutorial</code></a>, <a href="http://developer.android.com/training/articles/perf-jni.html" rel="nofollow"><code>this page</code></a>, and <a href="http://docs.oracle.com/javase/1.5.0/docs/guide/jni/spec/design.html#wp1242" rel="nofollow"><code>the oracle docs</code></a> don't have any information on the <code>NewGlobalRef</code> method itself.</p> <p><strong>EDIT</strong></p> <pre><code>jmethodID changeID; jmethodID getID; jmethodID putID; jmethodID flushID; jmethodID delayID; jobject myObject; jclass bluetoothClass; JNIEnv *myEnv; </code></pre>
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