参考：http://www.cnblogs.com/skywang12345/archive/2013/05/26/3093593.html
java 类:
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package
com.skywang.ndk;
public class MyInfo {
private
String mName;
private
int mAge;
private
float mHeight;
public
String toString(){
return
"mName:"+mName+", mAge:"+mAge+", mHeight:"+mHeight;
}
}============================================Person.java: package
com.skywang.ndk;
public
class Person {
private
String mName;
private
int mAge;
private
float mHeight;
public
String toString(){
return
"mName:"+mName+", mAge:"+mAge+", mHeight:"+mHeight;
}
} |
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package
com.skywang.ndk;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
public class NdkParam extends
Activity {
public
static final String TAG="skywang--NdkParam";
public
static final String TAG_MY="MY_skywang--NdkParam";
/** Called when the activity is first created. */
private
Person person=null;
private
MyInfo myinfo = null;
@Override
public
void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Log.d(TAG, "on create.");
person = new
Person();
for
(int i=0; i<3; i++) {
getPersonInfoByIndex(person, i);
Log.d(TAG, "person["+i+"] -- "+person);
}
Log.d(TAG, "==============================》MyInfo.《==================================");
myinfo = new
MyInfo();
for
(int i=0; i<3; i++) {
getMyInfoByIndex(myinfo, i);
Log.d(TAG, "myinfo["+i+"] -- "+myinfo);
}
}
// jni
private
native int getPersonInfoByIndex(Person person, int
index);
private
native int getMyInfoByIndex(MyInfo myinfo, int
index);
static
{
//System.loadLibrary("ndk_param");
System.loadLibrary("ndk_param");
}
} |
JNI:
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头文件：#include <stdlib.h>#include <string.h>#include <stdio.h>#include <jni.h>#include <assert.h>// 获取数组的大小# define NELEM(x) ((int) (sizeof(x) / sizeof((x)[0])))// 指定要注册的类，对应完整的java类名#define JNIREG_CLASS "com/skywang/ndk/NdkParam"#define JNIPAR_CLASS "com/skywang/ndk/Person"#define JNIPAR_CLASS_MYINFO "com/skywang/ndk/MyInfo"// 引入log头文件#include <android/log.h> // log标签#define TAG "hello_param"// 定义info信息#define LOGI(...) __android_log_print(ANDROID_LOG_INFO,TAG,__VA_ARGS__)// 定义debug信息#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, TAG, __VA_ARGS__)// 定义error信息#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,TAG,__VA_ARGS__)// jfieldID结构体，用于保存类“Person.java”的filedIDstruct
PersonOffsets
{ jfieldID name;
jfieldID age;
jfieldID height;
} gPersonOffsets;struct
MyInfoOffsets
{ jfieldID name;
jfieldID age;
jfieldID height;
} gMyInfoOffsets;// 与“Person.java”对应的结构体，用于保存数据，并将数据赋值给Person.java的成员typedef
struct tagPerson
{ char
mName[10];
int
mAge;
float
mHeight;
}Person;typedef
struct tagMyInfo
{ char
mName[10];
int
mAge;
float
mHeight;
}MyInfo;// 定义了3个Personstatic
Person gPersons[] = {
{"skywang", 25, 175},
{"eman"
, 30, 166},
{"Dan"
, 51, 172},
};static
MyInfo gMyInfos[] = {
{"liu", 25, 175},
{"gang"
, 30, 166},
{"hong"
, 51, 172},
};#define GPERSON_NUM NELEM(gPersons)#define GMYINFO_NUM NELEM(gMyInfos) |
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c文件：#include "ndk_param.h"/* * 根据index获取Person信息。
* 参数说明：
* env : JNI 接口指针。
* claszz : Java 类对象。
* person : 输入参数，java对象
* index : 输入参数，序列号。
*/
JNIEXPORT jint JNICALL getPersonInfoByIndex(JNIEnv *env, jobject clazz, jobject person, jint index){ // 若index无效，则直接返回-1。
if
((int)index<0 || (int)index>=GPERSON_NUM)
return
-1;
// 将Person数组(gPersons)中的第index个成员赋值给pPerson指针
Person *pPerson = &gPersons[index];
// 设置java对象person的mName
jstring name = (*env)->NewStringUTF(env, pPerson->mName);
(*env)->SetObjectField(env, person, gPersonOffsets.name, name);
// 设置java对象person的mAge
(*env)->SetIntField(env, person, gPersonOffsets.age, pPerson->mAge);
// 设置java对象person的mHeight
(*env)->SetFloatField(env, person, gPersonOffsets.height, pPerson->mHeight);
LOGD("%s index-%d mName:%s, mAge:%d, mHeight:%f\n",
__func__, index, pPerson->mName, pPerson->mAge, pPerson->mHeight);
return
0;
}JNIEXPORT jint JNICALL getMyInfoByIndex(JNIEnv *env, jobject clazz, jobject myinfo, jint index){ // 若index无效，则直接返回-1。
if
((int)index<0 || (int)index>=GMYINFO_NUM)
return
-1;
// 将Person数组(gPersons)中的第index个成员赋值给pPerson指针
MyInfo *pMyInfo = &gMyInfos[index];
// 设置java对象person的mName
jstring name = (*env)->NewStringUTF(env, pMyInfo->mName);
(*env)->SetObjectField(env, myinfo, gMyInfoOffsets.name, name);
// 设置java对象person的mAge
(*env)->SetIntField(env, myinfo, gMyInfoOffsets.age, pMyInfo->mAge);
// 设置java对象person的mHeight
(*env)->SetFloatField(env, myinfo, gMyInfoOffsets.height, pMyInfo->mHeight);
LOGD("%s index-%d mName:%s, mAge:%d, mHeight:%f\n",
__func__, index, pMyInfo->mName, pMyInfo->mAge, pMyInfo->mHeight);
return
0;
}// 初始化函数，用于获取Java中各个成员对应的fieldID。static
void nativeClassInit (JNIEnv *env)
{ jclass personClass = (*env)->FindClass(env, JNIPAR_CLASS);
jclass myinfoClass = (*env)->FindClass(env, JNIPAR_CLASS_MYINFO);
// 获取Person的mName成员对应的FieldID，并保存到gPersonOffsets中
gPersonOffsets.name = (*env)->GetFieldID(env, personClass, "mName"
, "Ljava/lang/String;");
gMyInfoOffsets.name = (*env)->GetFieldID(env, myinfoClass, "mName"
, "Ljava/lang/String;");
// 获取Person的mAge成员对应的FieldID，并保存到gPersonOffsets中
gPersonOffsets.age = (*env)->GetFieldID(env, personClass, "mAge"
, "I");
gMyInfoOffsets.age = (*env)->GetFieldID(env, myinfoClass, "mAge"
, "I");
// 获取Person的mHeight成员对应的FieldID，并保存到gPersonOffsets中
gPersonOffsets.height = (*env)->GetFieldID(env, personClass, "mHeight", "F");
gMyInfoOffsets.height = (*env)->GetFieldID(env, myinfoClass, "mHeight", "F");
}// Java和JNI函数的绑定表static
JNINativeMethod method_table[] = {
{ "getPersonInfoByIndex", "(Lcom/skywang/ndk/Person;I)I", (void*)getPersonInfoByIndex },//绑定
{ "getMyInfoByIndex", "(Lcom/skywang/ndk/MyInfo;I)I", (void*)getMyInfoByIndex },//绑定
};// 注册native方法到java中static
int registerNativeMethods(JNIEnv* env, const
char* className,
JNINativeMethod* gMethods, int
numMethods)
{ jclass clazz;
clazz = (*env)->FindClass(env, className);
if
(clazz == NULL) {
return
JNI_FALSE;
}
if
((*env)->RegisterNatives(env, clazz, gMethods, numMethods) < 0) {
return
JNI_FALSE;
}
return
JNI_TRUE;
}int
register_ndk_param(JNIEnv *env)
{ nativeClassInit(env);
// 调用注册方法
return
registerNativeMethods(env, JNIREG_CLASS,
method_table, NELEM(method_table));
}// JNI_OnLoad在jni注册时，会被回调执行。JNIEXPORT jint JNI_OnLoad(JavaVM* vm, void* reserved)
{ JNIEnv* env = NULL;
jint result = -1;
if
((*vm)->GetEnv(vm, (void**) &env, JNI_VERSION_1_4) != JNI_OK) {
return
result;
}
register_ndk_param(env);
// 返回jni的版本
return
JNI_VERSION_1_4;
} |