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POIssue calling back into Java from C++ called during a GLSurcfaceView callback
 

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  1. POIssue calling back into Java from C++ called during a GLSurcfaceView callback
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    <p>I have a GLSurfaceView created in a JAR file within my Android app. In the GLSurfaceView callback for onDrawFrame, I call a native C++ method via JNI. At this point, I believe I am in the GLThread, and in that native method, I am trying to call back into a Java class in my App's namespace and NOT into the namespace which made the call. So, I am trying to explicitly attach to the UI thread before doing so, but I am not successful.</p> <p>I am receiving the following error</p> <pre><code>W/dalvikvm( 4243): JNI WARNING: can't call Lcom/main/myapp;.updateView on instance of Lorg/myorg/myRenderer; W/dalvikvm( 4243): in Lorg/myorg/ImageRenderer;.renderImageFrame:()V (CallVoidMethodV) I/dalvikvm( 4243): "GLThread 336" prio=5 tid=16 RUNNABLE I/dalvikvm( 4243): | group="main" sCount=0 dsCount=0 obj=0x418029f8 self=0x400988a8 I/dalvikvm( 4243): | sysTid=4268 nice=0 sched=0/0 cgrp=apps handle=1362099424 I/dalvikvm( 4243): | schedstat=( 0 0 0 ) utm=83 stm=71 core=1 I/dalvikvm( 4243): at org.myorg.ImageRenderer.renderImageFrame(Native Method) I/dalvikvm( 4243): at org.myorg.ImageRenderer.onDrawFrame(ImageRenderer.java:93) I/dalvikvm( 4243): at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1516) I/dalvikvm( 4243): at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1240) </code></pre> <p>My C++ code looks like : </p> <pre><code>JavaVM * jvm; JNIEXPORT void JNICALL Java_org_myorg_ImageRenderer_renderImageFrame (JNIEnv *env, jobject jObj) { jvm-&gt;AttachCurrentThread(&amp;env, 0); jclass javaClass = env-&gt;FindClass("com/main/myapp"); if(javaClass == NULL){ LOGD("ERROR - CANNOT FIND CLASS"); } jfloatArray viewArray = env-&gt;NewFloatArray(16); env-&gt;SetFloatArrayRegion(viewArray, 0, 16, glmatrix.data); jmethodID method = env-&gt;GetMethodID(javaClass, "updateView", "([F)V"); if(method == NULL){ LOGD("ERROR - CANNOT ACCESS METHOD"); } env-&gt;CallVoidMethod(jObj, method, viewArray); env-&gt;DeleteLocalRef(viewArray); jvm-&gt;DetachCurrentThread(); } JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm, void* reserved){ jvm = vm; return JNI_VERSION_1_2; } </code></pre>
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    1. USBamerza
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    1. COThe warning is about a call to updateModel(), your code appears to be calling updateView(), so they don't quite line up. The error message is saying that the method isn't defined in the object you're passing in (the "this" pointer). You could try replacing the FindClass() with a GetObjectClass(jObj) and see if the GetMethodID call fails.
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      1. USfadden
    2. COSorry, I copy-pasted the wrong msg earlier. Edited it.
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      1. USBamerza
    3. COAnd, I originally tried with GetObjectClass() and had the same problem, that is why I switched to FindClass(). Either way, it can get/find the class and method, just cannot invoke the method.
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      1. POIssue calling back into Java from C++ called during a GLSurcfaceView callback
      1. USBamerza
 

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