====== 002 CからJavaの関数を実行する ======

===== 概要 =====
Androidには、NDKを利用してC/C++コード側からJavaのコードを呼ぶ機能が備わっています。
CallVoidMethod()やCallIntMethod() などがそれに当たります。

==== Javaのコード ====
<code java>
package com.hoge.hoge;

public class Sample
{
	public void Hello()
	{
		Log.v( "Hoge", "call Hello" );
	}
	
	public void SetParam( int _param )
	{
		Log.v( "Hoge", "call SetParam _param =" + _param );
	}
	
	public void SetParam2( int _param,  int _param2 )
	{
		Log.v( "Hoge", "call SetParam2 _param =" + _param + "_param2=" + _param2 );
	}
	
	public int GetParam()
	{
		Log.v( "Hoge", "call GetParam" );
	}
	
	public int GetParam2( int _param )
	{
		Log.v( "Hoge", "call GetParam2 = " + _param );
	}
}
</code>


==== Cのコード ====
<code c>
JavaVM * g_JVM = NULL;

extern "C" jint JNI_OnLoad(JavaVM* vm, void* reserved)
{
	JNIEnv* env;
	if( vm->GetEnv( reinterpret_cast<void**>(&env), JNI_VERSION_1_6) != JNI_OK )
	{
		return -1;
	}
	g_JVM  = vm;
}

void Func()
{
	jclass clazz = env->FindClass("com.hoge.hoge.Sample");
	jclass sampleClass = (jclass)env->NewGlobalRef( clazz );
	if( sampleClass == 0 )
	{
		return;
	}
	env->DeleteLocalRef( clazz );
	
	JNIEnv *env = NULL;
	int status = g_JVM->GetEnv((void **)&env, JNI_VERSION_1_6);
	if(status < 0)
	{
		status = g_JVM->AttachCurrentThread(&env, NULL);
		if(status < 0)
		{
			printf( 0, "error Func.\n" );
			return;
		}
	}
	
	// --------------------------------------
	// public void Hello()
	// --------------------------------------
	{
		jmethodID methodID = env->GetMethodID( sampleClass, "Hello", "()V" );
		env->CallVoidMethod( g_androidApp->activity->clazz, methodID );
	}
	
	// --------------------------------------
	// public void SetParam( int _param )
	// --------------------------------------
	{
		int param = 100;
		jmethodID methodID = env->GetMethodID( sampleClass, "SetParam", "(I)V" );
		env->CallVoidMethod( g_androidApp->activity->clazz, methodID, param );
	}
	
	// --------------------------------------
	// public void SetParam( int _param )
	// --------------------------------------
	{
		int param = 100;
		int param2 = 200;
		jmethodID methodID = env->GetMethodID( sampleClass, "SetParam2", "(II)V" );
		env->CallVoidMethod( g_androidApp->activity->clazz, methodID, param, param2 );
	}
	
	// --------------------------------------
	// public int GetParam()
	// --------------------------------------
	{
		jmethodID methodID = env->GetMethodID( sampleClass, "GetParam", "()I" );
		int ret = env->CallIntMethod( g_androidApp->activity->clazz, methodID );
	}
	
	// --------------------------------------
	// public int GetParam2()
	// --------------------------------------
	{
		int param = 100;
		jmethodID methodID = env->GetMethodID( sampleClass, "GetParam2", "(I)I" );
		int ret = env->CallIntMethod( g_androidApp->activity->clazz, methodID, param );
	}
}
</code>