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POcallback from pthread through JNI failing
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copied!<p>I'm trying to call back through JNI from a <code>pthread</code> created in a C++ class. With the following code. I can trigger a button press from my Android app and my <code>callbackStringJNI()</code> works fine. The creation of the <code>pthread</code> is triggered by a button press passed down through JNI. If the function/thread created by <code>pthread</code> attempts a asynchronous call of <code>callbackStringJNI()</code>, I do get the passed string in the Android app <code>messageMe()</code>(viewed only when breaking in debugger), but if I try to use the string(IE, display something on the UI), the application breaks on Android source 'Handler.class' function <code>joinThreadPool</code> and then if I resume again I hit the 'exception' in the Android code below:</p> <p>Android API Error Code:</p> <pre><code>public Handler(Callback callback, boolean async) { if (FIND_POTENTIAL_LEAKS) { final Class<? extends Handler> klass = getClass(); if ((klass.isAnonymousClass() || klass.isMemberClass() || klass.isLocalClass()) && (klass.getModifiers() & Modifier.STATIC) == 0) { Log.w(TAG, "The following Handler class should be static or leaks might occur: " + klass.getCanonicalName()); } } mLooper = Looper.myLooper(); if (mLooper == null) { throw new RuntimeException(//////////Hits here - this message is never actually displayed though. "Can't create handler inside thread that has not called Looper.prepare()"); } mQueue = mLooper.mQueue; mCallback = callback; mAsynchronous = async; } </code></pre> <p>I can copy the string to another variable as seen in the <code>messageMe()</code>, but I still can't use the string in a <code>Toast</code> or even a <code>TextView</code>. I am quite stumped at this time as to why I can not callback from a <code>pthread</code>, any suggestions are welcome.</p> <p>Android Java:</p> <pre><code> package com.example.somecontrol1; public class MainActivity extends Activity { // load the library - name matches jni/Android.mk static { System.loadLibrary("ndkfoo"); } private native String inintNativeClass(); private native String SetUpSocketNC(); private native void initJNICallback(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); initJNICallback(); inintNativeClass(); public void messageMe(String text) { String teststr = text; Toast.makeText(getApplicationContext(), teststr, Toast.LENGTH_LONG).show(); //appendTextAndScroll(text, gtv); } } </code></pre> <p>In the below code, when <code>getJNIEnv()</code> is called and the execution came from a button press, <code>JNI_OK</code> is the result. When the call comes from the callback in pthread, <code>JNI_EDETACHED</code> is the result and <code>AttachCurrentThread()</code> succeeds.</p> <p>JNI C ndkfoo.c</p> <pre><code>#include <jni.h> #include "testSocketClassWrapper.hpp" static JavaVM* cachedJVM; static jobject g_javaObj; static jclass cachedclassID; void *m_GBLpmyCSocket = NULL; jint JNI_OnLoad(JavaVM *jvm, void *reserved) { cachedJVM = jvm; JNIEnv* env; if ((*jvm)->GetEnv(jvm, (void **)&env, JNI_VERSION_1_4) != JNI_OK) { LOGD("GETENVFAILEDONLOAD"); return -1; } return JNI_VERSION_1_4; } void Java_com_example_somecontrol1_MainActivity_initJNICallback(JNIEnv* env, jobject jobj) { //LOGD("Java_org_test_games_Wrapper_initJNIBridge()"); g_javaObj = (*env)->NewGlobalRef(env, jobj); jclass storeclassID = (*env)->FindClass(env, "com/example/somecontrol1/MainActivity"); if ( (*env)->ExceptionCheck(env) == JNI_TRUE ){ (*env)->ExceptionDescribe(env); LOGD("got into exception describe"); } cachedclassID = (jclass)(*env)->NewGlobalRef(env, storeclassID); if ( (*env)->ExceptionCheck(env) == JNI_TRUE ){ (*env)->ExceptionDescribe(env); LOGD("got into exception describe"); } } jstring Java_com_example_somecontrol1_MainActivity_inintNativeClass(JNIEnv * env, jobject object){ m_GBLpmyCSocket = (void *)MyClass_create(); return (*env)->NewStringUTF(env, "launched class"); } typedef struct JniMethodInfo_ { JNIEnv* env; jclass classID; jmethodID methodID; } JniMethodInfo; static JNIEnv* getJNIEnv()//was JNIEnv { //JavaVM* jvm = cocos2d::JniHelper::getJavaVM(); if (NULL == cachedJVM) { LOGD("Failed to get JNIEnv. JniHelper::getJavaVM() is NULL"); return NULL; } JNIEnv *env = NULL; // get jni environment jint ret = (*cachedJVM)->GetEnv(cachedJVM, (void**)&env, JNI_VERSION_1_4); switch (ret) { case JNI_OK : // Success! LOGD("getenv successA"); return env; case JNI_EDETACHED : // Thread not attached LOGD("thread not attached"); // TODO : If calling AttachCurrentThread() on a native thread // must call DetachCurrentThread() in future. // see: http://developer.android.com/guide/practices/design/jni.html if ((*cachedJVM)->AttachCurrentThread(cachedJVM, &env, NULL) < 0) { LOGD("Failed to get the environment using AttachCurrentThread()"); return NULL; } else { // Success : Attached and obtained JNIEnv! LOGD("getenv successB"); return env; } case JNI_EVERSION : // Cannot recover from this error LOGD("JNI interface version 1.4 not supported"); default : LOGD("Failed to get the environment using GetEnv()"); return NULL; } } static bool getMethodInfo(JniMethodInfo *methodinfo, const char *methodName, const char *paramCode) { jmethodID methodID = 0; JNIEnv *pEnv = 0; bool bRet = false; do { pEnv = getJNIEnv(); if (! pEnv) { LOGD("getJNIEnv Break Called"); break; } //jclass classID = getClassID(pEnv); //jclass classID = cachedclassID; //methodID = (*pEnv)->GetMethodID(pEnv, classID, methodName, paramCode); methodID = (*pEnv)->GetMethodID(pEnv, cachedclassID, methodName, paramCode); if (! methodID) { LOGD("Failed to find method id of %s", methodName); break; } //methodinfo->classID = classID; methodinfo->env = pEnv; methodinfo->methodID = methodID; bRet = true; } while (0); return bRet; } void callbackStringJNI(const char *newstr) { LOGD("callbackStringJNI"); JniMethodInfo methodInfo; if (! getMethodInfo(&methodInfo, "messageMe", "(Ljava/lang/String;)V")) { LOGD("Cannot find method!"); return; } jstring jstr = (*methodInfo.env)->NewStringUTF(methodInfo.env, newstr); (*methodInfo.env)->CallVoidMethod(methodInfo.env, g_javaObj, methodInfo.methodID, jstr); } </code></pre> <p>Class wrapper</p> <pre><code>//file testSocketClassWrapper.cpp #include "testSocketClassWrapper.hpp" #include "testSocketClass.hpp" extern "C" void* MyClass_create() { return new mYNewClass; } extern "C" void MyClass_release(void* myclass) { delete static_cast<mYNewClass*>(myclass); } extern "C" void MyClass_sendCommandToSerialDevice(void* myclass, int cmd, int params, int id) { static_cast<mYNewClass*>(myclass)->sendCommandToSerialDevice(cmd,params,id); } extern "C" void SetUpSocket(void* myclass, int cmd, int params, int id) { static_cast<mYNewClass*>(myclass)->SetUpSocket(cmd,params,id); } extern "C" void Startcntl(void* myclass, int cmd, int params, int id) { static_cast<mYNewClass*>(myclass)->Startcntl(); } extern "C" void Stopcntl(void* myclass, int cmd, int params, int id) { static_cast<mYNewClass*>(myclass)->Stopcntl(); } </code></pre> <p>C++ class</p> <pre><code>//file testSocketClass.cpp void mYNewClass::SetUpSocket(int Command, int Parameters, int DeviceID){ thread1 = 0; iret1 = 0; iret1 = pthread_create( &thread1, NULL, &mYNewClass::thread_helper, this); } void mYNewClass::Startcntl(){ callbackStringJNI("sent start");//////this works. } </code></pre> <p>C++ header</p> <pre><code>//file testSocketClass.hpp extern "C" { void callbackStringJNI(const char *); } class mYNewClass{ public: void *threadfunc(void) { LOGD("in thread"); while(1){ LOGD("thread looping"); callbackStringJNI("readata start"); LOGD("sleep"); sleep(30); } LOGD("after callbackStringJNI");////this does not work return(0); } static void *thread_helper(void *context) { return ((mYNewClass *)context)->threadfunc(); } </code></pre>

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