JNI|在子线程中获得JNIEnv|AttachCurrentThread

最新推荐文章于 2024-07-23 14:00:25 发布

转载最新推荐文章于 2024-07-23 14:00:25 发布 · 1.5k 阅读

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

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本文详细介绍了如何在C++代码中通过JNI接口调用Java方法，包括初始化环境、获取JNI接口指针、处理不同通知ID的情况以及确保线程安全的断开连接。

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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]

[cpp]view plaincopy 
   
 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 );  
 }  