JNI中C和java传递数组

MainActivity

package com.example.arraydeliver;

import android.app.Activity;
import android.app.ActionBar;
import android.app.Fragment;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.os.Build;

public class MainActivity extends Activity {
		byte[] a=new byte[]{0x32,0x33,0x34,'\0'};

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		TextView tv= new TextView(this);
		tv.setText(stringFromJNI(a));
		setContentView(tv);

	}

	public native static String  stringFromJNI(byte[] a);

	static {
		System.loadLibrary("hello-jni");
	}
}

Native.c

#include <string.h>
#include <jni.h>
#include <stdlib.h>

typedef unsigned char byte;

JNIEXPORT jstring JNICALL Java_com_example_arraydeliver_MainActivity_stringFromJNI( JNIEnv* env,jobject thiz ,jbyteArray j){


	jbyte *temp=(*env)->GetByteArrayElements(env,j,0);
	char *x=(char *)temp;

	return (*env)->NewStringUTF(env,x+sizeof(x));

}

Android.mk

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := hello-jni

LOCAL_SRC_FILES := Native.c

include $(BUILD_SHARED_LIBRARY)

注意：在Native.c中的 GetByteArrayElements其实是获取java中的数组指针，所以在使用完后记得要释放(*env)->ReleaseByteArrayElements(env,j,temp,0)
注意2：C和C++中有些参数略有不同：C++中直接传入env->引用，C中则需要（×env）->,在C中 jbyte *temp=(*env)->GetByteArrayElements(env,j,0);
     而在C++中则 jbyte *temp=env->GetByteArrayElements(j,0);