[zz]JNI高级教程之数据类型转换
2014-04-02 09:45
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作者:陈波 2011/10/30(转载请注明出处,From:http://blog.csdn.net/jinhill/article/details/6918821)
最近做Android开发的人越来越多,Android开发难免会遇到调用本地库,这就需要采用JNI技术,JNI本身并不复杂,但大多数开发者在类型转换上遇到麻烦,今天特地将几种常用类型转换写成一个实例来告诉大家如何转换,尤其是Java的类和C的结构的转换,结构体中嵌套结构体如何处理,这部分网上的资料也比较少。
1. 编写Java类
package com.jinhill.util;
public class NativeModule {
public
native int testArg(int i, boolean b, char c, double d);
public
native byte[] testByte(byte[] b);
public
native String[] testString(String s, String[] sarr);
public
native int setInfo(MyInfo info);
public
native MyInfo getInfo();
static {
System.loadLibrary("NativeModule");
}
}
其中MyInfo类定义如下:
public class Record {
int id;
String
name;
byte[]
data;
}
public class MyInfo {
public
boolean b;
public char
c;
public
double d;
public int
i;
public
byte[] array;
public
String s;
public
Record rec;
}
C自定义结构体
typedef struct{
int id;
char
name[255];
char
data[255];
}Record;
typedef struct{
BOOL b;
char c;
double
d;
int i;
char
arr[255];
char
sz[255];
Record
rec;
}MyInfo;
2. 生成jni头文件
1) 编译javac
com/jinhill/util/NativeModule.java
2) javah
–jni com.jinhill.util.NativeModule
这样com_jinhill_util_NativeModule.h文件就生成好了。
3. 编写C库
1) Java与C不同类型参数转换实例
//不同类型参数处理
JNIEXPORT jintJNICALL
Java_com_jinhill_util_NativeModule_testArg
(JNIEnv *env, jobject jo, jint ji,
jbooleanjb, jchar jc, jdouble jd)
{
//获取jint型值
int i = ji;
//获取jboolean型值
BOOL b = jb;
//获取jdouble型值
double d = jd;
//获取jchar型值,Java的char两字节
char ch[5] = {0};
int size = 0;
size = WideCharToMultiByte(CP_ACP,NULL, (LPCWSTR)&jc, -1, ch,
5, NULL, FALSE);
if(size <= 0)
{
return -1;
}
Trace("ji=%d,jb=%d,jc=%s,jd=%lf",i, b, ch, d);
return 0;
}
2) Java
byte与C char数组类型数组转换实例
//btye数组处理,形参作为输入或输出,返回btye数组
JNIEXPORTjbyteArray JNICALL
Java_com_jinhill_util_NativeModule_testByte
(JNIEnv *env, jobject jo, jbyteArray jbArr)
{
char chTmp[] = "Hello JNI!";
int nTmpLen = strlen(chTmp);
//获取jbyteArray
char *chArr = (char*)env->GetByteArrayElements(jbArr,0);
//获取jbyteArray长度
int nArrLen = env->GetArrayLength(jbArr);
char *szStrBuf =(char*)malloc(nArrLen*2+10);
memset(szStrBuf, 0, nArrLen*2+10);
Bytes2String(chArr, nArrLen, szStrBuf,nArrLen*2+10);
Trace("jbArr=%s", szStrBuf);
//将jbArr作为输出形参
memset(chArr, 0, nArrLen);
memcpy(chArr, chTmp, nTmpLen);
//返回jbyteArray
jbyteArray jarrRV
=env->NewByteArray(nTmpLen);
jbyte *jby
=env->GetByteArrayElements(jarrRV, 0);
memcpy(jby, chTmp, strlen(chTmp));
env->SetByteArrayRegion(jarrRV, 0,nTmpLen,
jby);
return jarrRV;
}
3) Java
String与C char数组类型转换实例
//String 和String[]处理
JNIEXPORTjobjectArray JNICALL
Java_com_jinhill_util_NativeModule_testString
(JNIEnv *env, jobject jo, jstring
jstr,jobjectArray joarr)
{
int i = 0;
char chTmp[50] = {0};
//获取jstring值
const char* pszStr = (char*)env->GetStringUTFChars(jstr, 0);
Trace("jstr=%s", pszStr);
//获取jobjectArray值
int nArrLen =env->GetArrayLength(joarr);
Trace("joarr len=%d",nArrLen);
for(i=0; i
{
jstring js =(jstring)env->GetObjectArrayElement(joarr, i);
const char* psz = (char*)env->GetStringUTFChars(js, 0);
Trace("joarr[%d]=%s",i, psz);
}
//将joarr作为输出形参
jstring jstrTmp = NULL;
for(i=0; i
{
sprintf(chTmp, "No.%dHello JNI!", i);
jstrTmp =env->NewStringUTF(chTmp);
env->SetObjectArrayElement(joarr,i, jstrTmp);
env->DeleteLocalRef(jstrTmp);
}
//返回jobjectArray
jclass jstrCls =env->FindClass("Ljava/lang/String;");
jobjectArray jstrArray =env->NewObjectArray(2, jstrCls,
NULL);
for(i=0; i<2; i++)
{
sprintf(chTmp, "No. %dReturn JNI!", i);
jstrTmp =env->NewStringUTF(chTmp);
env->SetObjectArrayElement(jstrArray,i, jstrTmp);
env->DeleteLocalRef(jstrTmp);
}
return jstrArray;
}
4) Java
类与C结构体类型转换实例
JNIEXPORT jint JNICALL
Java_com_jinhill_util_NativeModule_setInfo
(JNIEnv *env, jobject jo, jobject jobj)
{
char
chHexTmp[512] = {0};
//将Java类转换成C结构体
MyInfo
mi;
//获取Java中的实例类Record
jclass jcRec
= env->FindClass("com/jinhill/util/Record");
//int id
jfieldID
jfid = env->GetFieldID(jcRec, "id", "I");
//String
name
jfieldID
jfname = env->GetFieldID(jcRec, "name",
"Ljava/lang/String;");
//byte[]
data;
jfieldID
jfdata = env->GetFieldID(jcRec, "data", "[B");
//获取Java中的实例类MyInfo
jclass
jcInfo = env->FindClass("com/jinhill/util/MyInfo");
//获取类中每一个变量的定义
//boolean
b
jfieldID jfb
= env->GetFieldID(jcInfo, "b", "Z");
//char c
jfieldID jfc
= env->GetFieldID(jcInfo, "c", "C");
//double
d
jfieldID jfd
= env->GetFieldID(jcInfo, "d", "D");
//int i
jfieldID jfi
= env->GetFieldID(jcInfo, "i", "I");
//byte[]
array
jfieldID jfa
= env->GetFieldID(jcInfo, "array", "[B");
//String
s
jfieldID jfs
= env->GetFieldID(jcInfo, "s", "Ljava/lang/String;");
//Record
rec;
jfieldID
jfrec = env->GetFieldID(jcInfo, "rec",
"Lcom/jinhill/util/Record;");
//获取实例的变量b的值
mi.b =
env->GetBooleanField(jobj, jfb);
//获取实例的变量c的值
jchar jc =
env->GetCharField(jobj, jfc);
char ch[5] =
{0};
int size =
0;
size =
WideCharToMultiByte(CP_ACP, NULL, (LPCWSTR)&jc, -1, ch, 5,
NULL, FALSE);
mi.c =
ch[0];
//获取实例的变量d的值
mi.d =
env->GetDoubleField(jobj, jfd);
//获取实例的变量i的值
mi.i =
env->GetIntField(jobj, jfi);
//获取实例的变量array的值
jbyteArray
ja = (jbyteArray)env->GetObjectField(jobj, jfa);
int nArrLen = env->GetArrayLength(ja);
char *chArr
= (char*)env->GetByteArrayElements(ja, 0);
memcpy(mi.arr, chArr, nArrLen);
//获取实例的变量s的值
jstring jstr
= (jstring)env->GetObjectField(jobj, jfs);
const char*
pszStr = (char*)env->GetStringUTFChars(jstr, 0);
strcpy(mi.sz, pszStr);
//获取Record对象
jobject
joRec = env->GetObjectField(jobj, jfrec);
//获取Record对象id值
mi.rec.id =
env->GetIntField(joRec, jfid);
Trace("mi.rec.id=%d",mi.rec.id);
//获取Record对象name值
jstring
jstrn = (jstring)env->GetObjectField(joRec, jfname);
pszStr =
(char*)env->GetStringUTFChars(jstrn, 0);
strcpy(mi.rec.name, pszStr);
//获取Record对象data值
jbyteArray
jbd = (jbyteArray)env->GetObjectField(joRec, jfdata);
nArrLen =
env->GetArrayLength(jbd);
chArr =
(char*)env->GetByteArrayElements(jbd, 0);
memcpy(mi.rec.data, chArr, nArrLen);
//日志输出
Bytes2String(mi.arr, nArrLen, chHexTmp,
sizeof(chHexTmp));
Trace("mi.arr=%s, mi.b=%d,
mi.c=%c, mi.d=%lf, mi.i=%d, \n mi.sz=%s\n mi.rec.id=%d,
mi.rec.name=%s", chHexTmp, mi.b, mi.c, mi.d, mi.i, mi.sz,
mi.rec.id, mi.rec.name);
return 0;
}
5) C结构体类型与Java
类转换实例
JNIEXPORT jobject JNICALL
Java_com_jinhill_util_NativeModule_getInfo
(JNIEnv *env, jobject jo)
{
wchar_t
wStr[255] = {0};
char chTmp[]
= "Hello JNI";
int nTmpLen
= strlen(chTmp);
//将C结构体转换成Java类
MyInfo
mi;
memcpy(mi.arr, chTmp, strlen(chTmp));
mi.b =
TRUE;
mi.c =
'B';
mi.d =
2000.9;
mi.i =
8;
strcpy(mi.sz, "Hello World!");
mi.rec.id =
2011;
memcpy(mi.rec.data, "\x01\x02\x03\x04\x05\x06", 6);
strcpy(mi.rec.name, "My JNI");
//获取Java中的实例类Record
jclass jcRec
= env->FindClass("com/jinhill/util/Record");
//int id
jfieldID
jfid = env->GetFieldID(jcRec, "id", "I");
//String
name
jfieldID
jfname = env->GetFieldID(jcRec, "name",
"Ljava/lang/String;");
//byte[]
data;
jfieldID
jfdata = env->GetFieldID(jcRec, "data", "[B");
//获取Java中的实例类
jclass
jcInfo = env->FindClass("com/jinhill/util/MyInfo");
//获取类中每一个变量的定义
//boolean
b
jfieldID jfb
= env->GetFieldID(jcInfo, "b", "Z");
//char c
jfieldID jfc
= env->GetFieldID(jcInfo, "c", "C");
//double
d
jfieldID jfd
= env->GetFieldID(jcInfo, "d", "D");
//int i
jfieldID jfi
= env->GetFieldID(jcInfo, "i", "I");
//byte[]
array
jfieldID jfa
= env->GetFieldID(jcInfo, "array", "[B");
//String
s
jfieldID jfs
= env->GetFieldID(jcInfo, "s", "Ljava/lang/String;");
//Record
rec;
jfieldID
jfrec = env->GetFieldID(jcInfo, "rec",
"Lcom/jinhill/util/Record;");
//创建新的对象
jobject
joRec = env->AllocObject(jcRec);
env->SetIntField(joRec, jfid, mi.rec.id);
jstring
jstrn = env->NewStringUTF(mi.rec.name);
env->SetObjectField(joRec, jfname, jstrn);
jbyteArray
jbarr = env->NewByteArray(6);
jbyte *jb =
env->GetByteArrayElements(jbarr, 0);
memcpy(jb,
mi.rec.data, 6);
env->SetByteArrayRegion(jbarr, 0, 6, jb);
env->SetObjectField(joRec, jfdata, jbarr);
//创建新的对象
jobject
joInfo = env->AllocObject(jcInfo);
//给类成员赋值
env->SetBooleanField(joInfo, jfb, mi.b);
// MultiByteToWideChar (CP_ACP, 0, mi.c, -1,
wStr, 255);
// env->SetCharField(joInfo, jfc,
(jchar)wStr);
env->SetCharField(joInfo, jfc, (jchar)mi.c);
env->SetDoubleField(joInfo, jfd, mi.d);
env->SetIntField(joInfo, jfi, mi.i);
jbyteArray
jarr = env->NewByteArray(nTmpLen);
jbyte *jby =
env->GetByteArrayElements(jarr, 0);
memcpy(jby,
mi.arr, nTmpLen);
env->SetByteArrayRegion(jarr, 0, nTmpLen, jby);
env->SetObjectField(joInfo, jfa, jarr);
jstring
jstrTmp = env->NewStringUTF(chTmp);
env->SetObjectField(joInfo, jfs, jstrTmp);
env->SetObjectField(joInfo, jfrec, joRec);
return
joInfo;
}
4. 编写Java测试代码
public class TestInfo {
public
static void main(String[] args) {
int i =0;
String[] sArr = new String[2];
for(i=0; i<2; i++)
{
sArr[i] = "ID=" + i;
}
byte[] b = new byte[10];
for(i=0; i<10; i++)
{
b[i] = (byte)i;
}
MyInfo mi = new MyInfo();
mi.array = b;
mi.b = false;
mi.c = 'C';
mi.d = 2011.11;
mi.i = 1752;
mi.s = "Hello World!";
mi.rec = new Record();
mi.rec.id = 2012;
mi.rec.name = "Record";
mi.rec.data = b;
NativeModule nm = new NativeModule();
nm.testArg(mi.i, mi.b, mi.c, mi.d);
byte[] b2[/u] =
nm.testByte(mi.array);
String[] s[/u] =
nm.testString(mi.s, sArr[/u]);
nm.setInfo(mi);
MyInfo mi2[/u] =
nm.getInfo();
System.out.println("finish");
}
}
5. Java String与 C
char数组转换时的中文问题
//将jstring类型转换成windows类型
char* jstringToWindows( JNIEnv *env, jstring jstr )
{
int length = (env)->GetStringLength(jstr );
const jchar* jcstr = (env)->GetStringChars(jstr, 0 );
char* rtn = (char*)malloc( length*2+1 );
int size = 0;
size = WideCharToMultiByte( CP_ACP, 0, (LPCWSTR)jcstr,
length,rtn,(length*2+1), NULL, NULL );
if( size <= 0 )
return NULL;
(env)->ReleaseStringChars(jstr, jcstr );
rtn[size] = 0;
return rtn;
}
//将windows类型转换成jstring类型
jstring WindowsTojstring( JNIEnv* env, char* str )
{
jstring rtn = 0;
int slen = strlen(str);
unsigned short * buffer = 0;
if( slen == 0 )
rtn = (env)->NewStringUTF(str );
else
{
int length = MultiByteToWideChar( CP_ACP, 0, (LPCSTR)str, slen,
NULL, 0 );
buffer = (unsigned short *)malloc( length*2 + 1 );
if( MultiByteToWideChar( CP_ACP, 0, (LPCSTR)str, slen,
(LPWSTR)buffer, length )>0 )
rtn = (env)->NewString( (jchar*)buffer, length );
}
if( buffer )
free( buffer );
return rtn;
}
最近做Android开发的人越来越多,Android开发难免会遇到调用本地库,这就需要采用JNI技术,JNI本身并不复杂,但大多数开发者在类型转换上遇到麻烦,今天特地将几种常用类型转换写成一个实例来告诉大家如何转换,尤其是Java的类和C的结构的转换,结构体中嵌套结构体如何处理,这部分网上的资料也比较少。
1. 编写Java类
package com.jinhill.util;
public class NativeModule {
public
native int testArg(int i, boolean b, char c, double d);
public
native byte[] testByte(byte[] b);
public
native String[] testString(String s, String[] sarr);
public
native int setInfo(MyInfo info);
public
native MyInfo getInfo();
static {
System.loadLibrary("NativeModule");
}
}
其中MyInfo类定义如下:
public class Record {
int id;
String
name;
byte[]
data;
}
public class MyInfo {
public
boolean b;
public char
c;
public
double d;
public int
i;
public
byte[] array;
public
String s;
public
Record rec;
}
C自定义结构体
typedef struct{
int id;
char
name[255];
char
data[255];
}Record;
typedef struct{
BOOL b;
char c;
double
d;
int i;
char
arr[255];
char
sz[255];
Record
rec;
}MyInfo;
2. 生成jni头文件
1) 编译javac
com/jinhill/util/NativeModule.java
2) javah
–jni com.jinhill.util.NativeModule
这样com_jinhill_util_NativeModule.h文件就生成好了。
3. 编写C库
1) Java与C不同类型参数转换实例
//不同类型参数处理
JNIEXPORT jintJNICALL
Java_com_jinhill_util_NativeModule_testArg
(JNIEnv *env, jobject jo, jint ji,
jbooleanjb, jchar jc, jdouble jd)
{
//获取jint型值
int i = ji;
//获取jboolean型值
BOOL b = jb;
//获取jdouble型值
double d = jd;
//获取jchar型值,Java的char两字节
char ch[5] = {0};
int size = 0;
size = WideCharToMultiByte(CP_ACP,NULL, (LPCWSTR)&jc, -1, ch,
5, NULL, FALSE);
if(size <= 0)
{
return -1;
}
Trace("ji=%d,jb=%d,jc=%s,jd=%lf",i, b, ch, d);
return 0;
}
2) Java
byte与C char数组类型数组转换实例
//btye数组处理,形参作为输入或输出,返回btye数组
JNIEXPORTjbyteArray JNICALL
Java_com_jinhill_util_NativeModule_testByte
(JNIEnv *env, jobject jo, jbyteArray jbArr)
{
char chTmp[] = "Hello JNI!";
int nTmpLen = strlen(chTmp);
//获取jbyteArray
char *chArr = (char*)env->GetByteArrayElements(jbArr,0);
//获取jbyteArray长度
int nArrLen = env->GetArrayLength(jbArr);
char *szStrBuf =(char*)malloc(nArrLen*2+10);
memset(szStrBuf, 0, nArrLen*2+10);
Bytes2String(chArr, nArrLen, szStrBuf,nArrLen*2+10);
Trace("jbArr=%s", szStrBuf);
//将jbArr作为输出形参
memset(chArr, 0, nArrLen);
memcpy(chArr, chTmp, nTmpLen);
//返回jbyteArray
jbyteArray jarrRV
=env->NewByteArray(nTmpLen);
jbyte *jby
=env->GetByteArrayElements(jarrRV, 0);
memcpy(jby, chTmp, strlen(chTmp));
env->SetByteArrayRegion(jarrRV, 0,nTmpLen,
jby);
return jarrRV;
}
3) Java
String与C char数组类型转换实例
//String 和String[]处理
JNIEXPORTjobjectArray JNICALL
Java_com_jinhill_util_NativeModule_testString
(JNIEnv *env, jobject jo, jstring
jstr,jobjectArray joarr)
{
int i = 0;
char chTmp[50] = {0};
//获取jstring值
const char* pszStr = (char*)env->GetStringUTFChars(jstr, 0);
Trace("jstr=%s", pszStr);
//获取jobjectArray值
int nArrLen =env->GetArrayLength(joarr);
Trace("joarr len=%d",nArrLen);
for(i=0; i
{
jstring js =(jstring)env->GetObjectArrayElement(joarr, i);
const char* psz = (char*)env->GetStringUTFChars(js, 0);
Trace("joarr[%d]=%s",i, psz);
}
//将joarr作为输出形参
jstring jstrTmp = NULL;
for(i=0; i
{
sprintf(chTmp, "No.%dHello JNI!", i);
jstrTmp =env->NewStringUTF(chTmp);
env->SetObjectArrayElement(joarr,i, jstrTmp);
env->DeleteLocalRef(jstrTmp);
}
//返回jobjectArray
jclass jstrCls =env->FindClass("Ljava/lang/String;");
jobjectArray jstrArray =env->NewObjectArray(2, jstrCls,
NULL);
for(i=0; i<2; i++)
{
sprintf(chTmp, "No. %dReturn JNI!", i);
jstrTmp =env->NewStringUTF(chTmp);
env->SetObjectArrayElement(jstrArray,i, jstrTmp);
env->DeleteLocalRef(jstrTmp);
}
return jstrArray;
}
4) Java
类与C结构体类型转换实例
JNIEXPORT jint JNICALL
Java_com_jinhill_util_NativeModule_setInfo
(JNIEnv *env, jobject jo, jobject jobj)
{
char
chHexTmp[512] = {0};
//将Java类转换成C结构体
MyInfo
mi;
//获取Java中的实例类Record
jclass jcRec
= env->FindClass("com/jinhill/util/Record");
//int id
jfieldID
jfid = env->GetFieldID(jcRec, "id", "I");
//String
name
jfieldID
jfname = env->GetFieldID(jcRec, "name",
"Ljava/lang/String;");
//byte[]
data;
jfieldID
jfdata = env->GetFieldID(jcRec, "data", "[B");
//获取Java中的实例类MyInfo
jclass
jcInfo = env->FindClass("com/jinhill/util/MyInfo");
//获取类中每一个变量的定义
//boolean
b
jfieldID jfb
= env->GetFieldID(jcInfo, "b", "Z");
//char c
jfieldID jfc
= env->GetFieldID(jcInfo, "c", "C");
//double
d
jfieldID jfd
= env->GetFieldID(jcInfo, "d", "D");
//int i
jfieldID jfi
= env->GetFieldID(jcInfo, "i", "I");
//byte[]
array
jfieldID jfa
= env->GetFieldID(jcInfo, "array", "[B");
//String
s
jfieldID jfs
= env->GetFieldID(jcInfo, "s", "Ljava/lang/String;");
//Record
rec;
jfieldID
jfrec = env->GetFieldID(jcInfo, "rec",
"Lcom/jinhill/util/Record;");
//获取实例的变量b的值
mi.b =
env->GetBooleanField(jobj, jfb);
//获取实例的变量c的值
jchar jc =
env->GetCharField(jobj, jfc);
char ch[5] =
{0};
int size =
0;
size =
WideCharToMultiByte(CP_ACP, NULL, (LPCWSTR)&jc, -1, ch, 5,
NULL, FALSE);
mi.c =
ch[0];
//获取实例的变量d的值
mi.d =
env->GetDoubleField(jobj, jfd);
//获取实例的变量i的值
mi.i =
env->GetIntField(jobj, jfi);
//获取实例的变量array的值
jbyteArray
ja = (jbyteArray)env->GetObjectField(jobj, jfa);
int nArrLen = env->GetArrayLength(ja);
char *chArr
= (char*)env->GetByteArrayElements(ja, 0);
memcpy(mi.arr, chArr, nArrLen);
//获取实例的变量s的值
jstring jstr
= (jstring)env->GetObjectField(jobj, jfs);
const char*
pszStr = (char*)env->GetStringUTFChars(jstr, 0);
strcpy(mi.sz, pszStr);
//获取Record对象
jobject
joRec = env->GetObjectField(jobj, jfrec);
//获取Record对象id值
mi.rec.id =
env->GetIntField(joRec, jfid);
Trace("mi.rec.id=%d",mi.rec.id);
//获取Record对象name值
jstring
jstrn = (jstring)env->GetObjectField(joRec, jfname);
pszStr =
(char*)env->GetStringUTFChars(jstrn, 0);
strcpy(mi.rec.name, pszStr);
//获取Record对象data值
jbyteArray
jbd = (jbyteArray)env->GetObjectField(joRec, jfdata);
nArrLen =
env->GetArrayLength(jbd);
chArr =
(char*)env->GetByteArrayElements(jbd, 0);
memcpy(mi.rec.data, chArr, nArrLen);
//日志输出
Bytes2String(mi.arr, nArrLen, chHexTmp,
sizeof(chHexTmp));
Trace("mi.arr=%s, mi.b=%d,
mi.c=%c, mi.d=%lf, mi.i=%d, \n mi.sz=%s\n mi.rec.id=%d,
mi.rec.name=%s", chHexTmp, mi.b, mi.c, mi.d, mi.i, mi.sz,
mi.rec.id, mi.rec.name);
return 0;
}
5) C结构体类型与Java
类转换实例
JNIEXPORT jobject JNICALL
Java_com_jinhill_util_NativeModule_getInfo
(JNIEnv *env, jobject jo)
{
wchar_t
wStr[255] = {0};
char chTmp[]
= "Hello JNI";
int nTmpLen
= strlen(chTmp);
//将C结构体转换成Java类
MyInfo
mi;
memcpy(mi.arr, chTmp, strlen(chTmp));
mi.b =
TRUE;
mi.c =
'B';
mi.d =
2000.9;
mi.i =
8;
strcpy(mi.sz, "Hello World!");
mi.rec.id =
2011;
memcpy(mi.rec.data, "\x01\x02\x03\x04\x05\x06", 6);
strcpy(mi.rec.name, "My JNI");
//获取Java中的实例类Record
jclass jcRec
= env->FindClass("com/jinhill/util/Record");
//int id
jfieldID
jfid = env->GetFieldID(jcRec, "id", "I");
//String
name
jfieldID
jfname = env->GetFieldID(jcRec, "name",
"Ljava/lang/String;");
//byte[]
data;
jfieldID
jfdata = env->GetFieldID(jcRec, "data", "[B");
//获取Java中的实例类
jclass
jcInfo = env->FindClass("com/jinhill/util/MyInfo");
//获取类中每一个变量的定义
//boolean
b
jfieldID jfb
= env->GetFieldID(jcInfo, "b", "Z");
//char c
jfieldID jfc
= env->GetFieldID(jcInfo, "c", "C");
//double
d
jfieldID jfd
= env->GetFieldID(jcInfo, "d", "D");
//int i
jfieldID jfi
= env->GetFieldID(jcInfo, "i", "I");
//byte[]
array
jfieldID jfa
= env->GetFieldID(jcInfo, "array", "[B");
//String
s
jfieldID jfs
= env->GetFieldID(jcInfo, "s", "Ljava/lang/String;");
//Record
rec;
jfieldID
jfrec = env->GetFieldID(jcInfo, "rec",
"Lcom/jinhill/util/Record;");
//创建新的对象
jobject
joRec = env->AllocObject(jcRec);
env->SetIntField(joRec, jfid, mi.rec.id);
jstring
jstrn = env->NewStringUTF(mi.rec.name);
env->SetObjectField(joRec, jfname, jstrn);
jbyteArray
jbarr = env->NewByteArray(6);
jbyte *jb =
env->GetByteArrayElements(jbarr, 0);
memcpy(jb,
mi.rec.data, 6);
env->SetByteArrayRegion(jbarr, 0, 6, jb);
env->SetObjectField(joRec, jfdata, jbarr);
//创建新的对象
jobject
joInfo = env->AllocObject(jcInfo);
//给类成员赋值
env->SetBooleanField(joInfo, jfb, mi.b);
// MultiByteToWideChar (CP_ACP, 0, mi.c, -1,
wStr, 255);
// env->SetCharField(joInfo, jfc,
(jchar)wStr);
env->SetCharField(joInfo, jfc, (jchar)mi.c);
env->SetDoubleField(joInfo, jfd, mi.d);
env->SetIntField(joInfo, jfi, mi.i);
jbyteArray
jarr = env->NewByteArray(nTmpLen);
jbyte *jby =
env->GetByteArrayElements(jarr, 0);
memcpy(jby,
mi.arr, nTmpLen);
env->SetByteArrayRegion(jarr, 0, nTmpLen, jby);
env->SetObjectField(joInfo, jfa, jarr);
jstring
jstrTmp = env->NewStringUTF(chTmp);
env->SetObjectField(joInfo, jfs, jstrTmp);
env->SetObjectField(joInfo, jfrec, joRec);
return
joInfo;
}
4. 编写Java测试代码
public class TestInfo {
public
static void main(String[] args) {
int i =0;
String[] sArr = new String[2];
for(i=0; i<2; i++)
{
sArr[i] = "ID=" + i;
}
byte[] b = new byte[10];
for(i=0; i<10; i++)
{
b[i] = (byte)i;
}
MyInfo mi = new MyInfo();
mi.array = b;
mi.b = false;
mi.c = 'C';
mi.d = 2011.11;
mi.i = 1752;
mi.s = "Hello World!";
mi.rec = new Record();
mi.rec.id = 2012;
mi.rec.name = "Record";
mi.rec.data = b;
NativeModule nm = new NativeModule();
nm.testArg(mi.i, mi.b, mi.c, mi.d);
byte[] b2[/u] =
nm.testByte(mi.array);
String[] s[/u] =
nm.testString(mi.s, sArr[/u]);
nm.setInfo(mi);
MyInfo mi2[/u] =
nm.getInfo();
System.out.println("finish");
}
}
5. Java String与 C
char数组转换时的中文问题
//将jstring类型转换成windows类型
char* jstringToWindows( JNIEnv *env, jstring jstr )
{
int length = (env)->GetStringLength(jstr );
const jchar* jcstr = (env)->GetStringChars(jstr, 0 );
char* rtn = (char*)malloc( length*2+1 );
int size = 0;
size = WideCharToMultiByte( CP_ACP, 0, (LPCWSTR)jcstr,
length,rtn,(length*2+1), NULL, NULL );
if( size <= 0 )
return NULL;
(env)->ReleaseStringChars(jstr, jcstr );
rtn[size] = 0;
return rtn;
}
//将windows类型转换成jstring类型
jstring WindowsTojstring( JNIEnv* env, char* str )
{
jstring rtn = 0;
int slen = strlen(str);
unsigned short * buffer = 0;
if( slen == 0 )
rtn = (env)->NewStringUTF(str );
else
{
int length = MultiByteToWideChar( CP_ACP, 0, (LPCSTR)str, slen,
NULL, 0 );
buffer = (unsigned short *)malloc( length*2 + 1 );
if( MultiByteToWideChar( CP_ACP, 0, (LPCSTR)str, slen,
(LPWSTR)buffer, length )>0 )
rtn = (env)->NewString( (jchar*)buffer, length );
}
if( buffer )
free( buffer );
return rtn;
}
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