JNI|在子线程中获得JNIEnv|AttachCurrentThread

最新推荐文章于 2025-06-03 09:03:10 发布

原创最新推荐文章于 2025-06-03 09:03:10 发布 · 2.8w 阅读

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CC 4.0 BY-SA版权

文章标签：

#jni #thread #interface #callback #jvm #null

本文详细介绍了JNI接口指针在Java方法映射到本地方法时的作用，阐述了如何通过JNI接口指针进行交互，以及在不同线程中的使用和生命周期管理。重点分析了回调函数的实现，包括获取JNI环境、线程绑定、方法调用以及线程安全考虑。

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A JNI interface pointer (JNIEnv*) is passed as an argument for each native function mapped to a Java method, allowing for interaction with the JNI environment within the native method.This JNI interface pointer can be stored, but remains valid only in the current thread. Other threads must first call AttachCurrentThread()to attach themselves to the VM and obtain a JNI interface pointer. Once attached, a native thread works like a regular Java thread running within a native method. The native thread remains attached to the VM until it callsDetachCurrentThread() to detach itself.[3]

void Call_Back_Invoke( void *user,int notify_id, unsigned int param )
{
	bool  isAttacked = false;
	JNIEnv* env;
	if(NULL == jni_tmpc.g_JVM)
	{
		LOGE("g_JVM == NULL");
		return ;
	}
	int status = (jni_tmpc.g_JVM)->GetEnv((void **) &env, jni_tmpc.g_JNI_VERSION);

	if(status < 0) {
		LOGD("callback_handler:failed to get JNI environment assuming native thread"); 
		status = jni_tmpc.g_JVM->AttachCurrentThread(&env, NULL);
		if(status < 0) {
		   LOGE("callback_handler: failed to attach current thread");
		    return;
		}
		isAttacked = true;
	}

	switch( notify_id )
    {
   	case...
		 ...
    }	
	if(isAttacked) 
	{
		(jni_tmpc.g_JVM)->DetachCurrentThread();
	}	
	LOGE("jni Call_Back_Invoke(1) notify_id = %d",notify_id );
}