issues cocos2d#2899:Fix application will crash when back to background on Android.

Author: WenhaiLin

cocos2dx/platform/android/jni/JniHelper.cpp

@@ -58,6 +58,8 @@ namespace cocos2d {
     jobject JniHelper::classloader = NULL;
     JNIEnv* JniHelper::env = NULL;
 
+    static pthread_key_t thread_key;
+
     JavaVM* JniHelper::getJavaVM() {
         pthread_t thisthread = pthread_self();
         LOGD("JniHelper::getJavaVM(), pthread_self() = %X", thisthread);
@@ -72,6 +74,10 @@ namespace cocos2d {
         JniHelper::cacheEnv(javaVM);
     }
 
+    void JniHelper::detach_current_thread (void *env) {
+        _psJavaVM->DetachCurrentThread();
+    }
+
     bool JniHelper::cacheEnv(JavaVM* jvm) {
         JNIEnv* _env = NULL;
         // get jni environment
@@ -89,7 +95,8 @@ namespace cocos2d {
             // TODO : If calling AttachCurrentThread() on a native thread
             // must call DetachCurrentThread() in future.
             // see: http://developer.android.com/guide/practices/design/jni.html
-                
+            
+            pthread_key_create (&thread_key, JniHelper::detach_current_thread);
             if (jvm->AttachCurrentThread(&_env, NULL) < 0)
                 {
                     LOGD("Failed to get the environment using AttachCurrentThread()");
@@ -99,6 +106,8 @@ namespace cocos2d {
                 } else {
                 // Success : Attached and obtained JNIEnv!
                 JniHelper::env = _env;
+                if (pthread_getspecific(thread_key) == NULL)
+                    pthread_setspecific(thread_key, _env); 
                 return true;
             }
 

cocos2dx/platform/android/jni/JniHelper.h

@@ -60,6 +60,7 @@ class CC_DLL JniHelper
     static jobject classloader;
 
 private:
+    static void detach_current_thread (void *env);
     static bool cacheEnv(JavaVM* jvm);
 
     static bool getMethodInfo_DefaultClassLoader(JniMethodInfo &methodinfo,

cocos2dx/platform/android/nativeactivity.cpp

@@ -215,10 +215,10 @@ static cocos_dimensions engine_init_display(struct engine* engine) {
 /**
  * Invoke the dispatching of the next bunch of Runnables in the Java-Land
  */
+static bool initialized = false;
 static void dispatch_pending_runnables() {
     static cocos2d::JniMethodInfo info;
-    static bool initialized = false;
-
+    
     if (!initialized) {
         initialized = cocos2d::JniHelper::getStaticMethodInfo(
             info,
@@ -652,7 +652,7 @@ void android_main(struct android_app* state) {
                 engine_term_display(&engine);
 
                 memset(&engine, 0, sizeof(engine));
-
+                initialized = false;
                 return;
             }
         }