JNI中C和java传递数组

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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'};@Overrideprotected 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-jniLOCAL_SRC_FILES := Native.cinclude $(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);

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