Of the top of my head, I think you need to createThreadEtc with the
flag to indicate that your thread will call into Java.
On Jan 9, 2:00 pm, "redlight9...@gmail.com" <redlight9...@gmail.com>
wrote:
> i am trying to make callbacks to my android application from a native
> C thread using JNI. however when i call FindClass it returns a NULL
> value. i need to get the jclass value returned by FindClass() to
> call GetStaticMethoID to make calls back up to my android application.
>
> i store the JavaVM* globally that i receive from JNI_OnLoad which gets
> called from the android thread when my application loads my shared
> library. I then use that JavaVM* to attach the java virtual machine
> to my native C thread by calling AttachCurrentThread() which returns a
> 0 value indicating success.
>
> the weird thing is that when i make calls to FindClass() in the
> android thread it works fine and returns a valid value. however when
> i call FindClass() from the native C thread it returns NULL. I was
> thinking that it might have something to do with the native C thread
> not have the proper classpath set up? any help would be greatly
> appreciated.
>
> my code is down below, i omitted error checking and some of the code
> to save space.
>
> #include "JNIHelp.h"
> #include "jni.h"
> #include "utils/Log.h"
>
> static JavaVM *jvm;
>
> static void androidCback(int event)
> {
> jint r;
> jclass cls;
> JNIEnv *env;
> jmethodID mid;
>
> r = (*jvm)->AttachCurrentThread(jvm, &env, NULL);
>
> /* !!! FindClass returns NULL !!! */
> cls = (*env)->FindClass(env, "com.android.SomeApp.Class");
>
> mid = (*env)->GetStaticMethodID(env, cls, "handleEvent", "(I)V");
> (*jvm)->DetachCurrentThread(jvm);
>
> }
>
> JNIEXPORT jint JNI_OnLoad(JavaVM *vm, void *reserved)
>
> {
>
> JNIEnv *env;
>
> JNINativeMethod meth;
>
> jclass k;
>
> jint r;
>
> r = (*vm)->GetEnv (vm, (void **) &env, JNI_VERSION_1_4);
>
> /* !!! FindClass returns valid value !!! */
> k = (*env)->FindClass (env, "com.android.SomeApp.Class");
>
> /* save the java virtual machine globally */
> jvm = vm;
>
> meth.name = "enableNative";
>
> meth.signature = "(I)Z";
>
> meth.fnPtr = enableNative;
>
> r = (*env)->RegisterNatives (env, k, &meth, 1);
>
> }
>
> JNIEXPORT void JNI_OnUnload(JavaVM *vm, void *reserved)
>
> {
>
> JNIEnv *env;
>
> jclass k;
>
> jint r;
>
> r = (*vm)->GetEnv (vm, (void **) &env, JNI_VERSION_1_4);
>
> /* !!! FindClass returns valid value !!! */
> k = (*env)->FindClass (env, "com.android.SomeApp.Class");
>
> (*env)->UnregisterNatives(env, k);
>
> }
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