JNI由浅入深_10_JNI 综合开发

1、使用ndk-build时如果找不到某个类，可以使用下面两种方法解决：

1、1 进入src目录

D:\project3\JNIAndroid\src>set classpath=D:\project3\JNIAndroid\src

1、2 设置classpath

classpath .;%JAVA_HOME%\lib\dt.jar;%JAVA_HOME%\tools.jar;E:\developLib\android\platforms\android-8\android.jar

2、基础类

ublic 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 结构体定义

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;

3、编写C库

3.1) 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;

}

3.2) 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;

}

3.3) 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<nArrLen; 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<nArrLen; 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;

}

3.4) 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;

}

3.5) 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;

}

3.6) 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 )

{

<span style="white-space:pre">	</span>int length = (env)->GetStringLength(jstr );

<span style="white-space:pre">	</span>const jchar* jcstr = (env)->GetStringChars(jstr, 0 );

<span style="white-space:pre">	</span>char* rtn = (char*)malloc( length*2+1 );

<span style="white-space:pre">	</span>int size = 0;

<span style="white-space:pre">	</span>size = WideCharToMultiByte( CP_ACP, 0, (LPCWSTR)jcstr, length,rtn,(length*2+1), NULL, NULL );

<span style="white-space:pre">	</span>if( size <= 0 )

<span style="white-space:pre">		</span>return NULL;

<span style="white-space:pre">	</span>(env)->ReleaseStringChars(jstr, jcstr );

<span style="white-space:pre">	</span>rtn[size] = 0;

<span style="white-space:pre">	</span>return rtn;

}

//将windows类型转换成jstring类型

jstring WindowsTojstring( JNIEnv* env, char* str )

{

<span style="white-space:pre">	</span>jstring rtn = 0;

<span style="white-space:pre">	</span>int slen = strlen(str);

<span style="white-space:pre">	</span>unsigned short * buffer = 0;

<span style="white-space:pre">	</span>if( slen == 0 )

<span style="white-space:pre">		</span>rtn = (env)->NewStringUTF(str );

<span style="white-space:pre">	</span>else

<span style="white-space:pre">	</span>{

<span style="white-space:pre">		</span>int length = MultiByteToWideChar( CP_ACP, 0, (LPCSTR)str, slen, NULL, 0 );

<span style="white-space:pre">		</span>buffer = (unsigned short *)malloc( length*2 + 1 );

<span style="white-space:pre">		</span>if( MultiByteToWideChar( CP_ACP, 0, (LPCSTR)str, slen, (LPWSTR)buffer, length )>0 )

<span style="white-space:pre">			</span>rtn = (env)->NewString( (jchar*)buffer, length );

<span style="white-space:pre">	</span>}

<span style="white-space:pre">	</span>if( buffer )

<span style="white-space:pre">		</span>free( buffer );

<span style="white-space:pre">	</span>return rtn;

}

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