更新时间:2021-11-13 02:06:31
想要调用本地C ++代码,而你又要调用一个java方法。这实际上有点棘手。
The complication here is that you want to invoke native C++ code which you, in turn, want to invoke a java method. This is actually a bit tricky.
您需要创建一个用于java调用的JNI C ++函数,以及一个与
匹配的C ++函数MyCPPFunction回调签名。后者将作为一个包装器来调用java方法。
You need to create a JNI C++ function for java to call, and a C++ function matching the MyCPPFunction callback signature. The latter will act as a wrapper to call the java method.
因为包装器将需要关于JNI环境的信息,这不能由参数提供(为了破坏签名),你创建一些全局变量来保存它: / p>
Because the wrapper will need information about the JNI environment, which cannot be provided by parameters (lest we ruin the signature) you create a few global variables to hold it:
jobject g_getSizeIface;
jmethodID g_method;
JNIEnv *g_env;
java将调用的C ++函数如下:
The C++ function which java will call is the following:
JNIEXPORT void JNICALL Java_ClassName_MyCPPFunction
(JNIEnv *env, jint size, jobject getSizeInterface)
{
jclass objclass = env->GetObjectClass(getSizeInterface);
jmethodID method = env->GetMethodID(objclass, "GetSize", "(m_SizeClass)I");
if(methodID == 0){
cout << "could not get method id!\n";
return;
}
g_method = method;
g_getSizeIface = getSizeInterface;
g_env = env
MyCPPFunction(size, WrapperFunc);
}
而且包装函数是:
int WrapperFunc(int *id)
{
jint retval;
//marshalling an int* to a m_SizeClass boogy-woogy.
...
g_env->ExceptionClear();
retval = g_env->CallIntMethod(g_getSizeIface, g_method,
/*marshalled m_SizeClass*/);
if(g_env->ExceptionOccured()){
//panic! Light fires! The British are coming!!!
...
g_env->ExceptionClear();
}
return rvalue;
}