java jni使用之将java的 string[ ] 字符串数组转化成c语言的 char-凯发app官方网站

用java直接调用c里面的main(int argc,*char[] argv),那么在java层面上，就需要使用string[]字符串数组，然后将string[]转化成c语言的char**。

   根据前面的文章，制作调用jni的c头文件:
   
/* do not edit this file - it is machine generated */
#include "jni.h"
/* header for class com_xmu_engine_htk */
                                                                                                                                                                                   
#ifndef _included_com_xmu_engine_htk
#define _included_com_xmu_engine_htk
#ifdef __cplusplus
extern "c" {
#endif
/*
 * class:     com_xmu_engine_htk
 * method:    hcopy
 * signature: ([ljava/lang/string;)[ljava/lang/string;
 */
jniexport jobjectarray jnicall java_com_xmu_engine_htk_hcopy
  (jnienv *, jclass, jobjectarray);
/*
 * class:     com_xmu_engine_htk
 * method:    hvite
 * signature: ([ljava/lang/string;)v
 */
jniexport void jnicall java_com_xmu_engine_htk_hvite
  (jnienv *, jclass, jobjectarray);
                                                                                                                                                                                   
/*
 * class:     com_xmu_engine_htk
 * method:    hparse
 * signature: ([ljava/lang/string;)v
 */
jniexport void jnicall java_com_xmu_engine_htk_hparse
  (jnienv *, jclass, jobjectarray);
                                                                                                                                                                                   
#ifdef __cplusplus
}
#endif
#endif


   我们看到，jobjectarray就是c的jni定义的string字符串数组。这三个函数在java中的声明：
   
package com.xmu.engine;
                                                                
public class htk {
    public static native void hcopy(string args[]);
                                                                
    public static native void hvite(string args[]);
                                                                
    public static native void hparse(string args[]);
                                                                
    static {
        system.loadlibrary("htkengine");
    }
}


   下面，重点来看看怎样将java string[]转化按成c的char**（看其中的hvite如何实现，其余两个类似）：

    
/*
 * class:     com_xmu_engine_htk
 * method:    hvite
 * signature: ()v
 */
jniexport void jnicall java_com_xmu_engine_htk_hvite
    (jnienv * env, jclass jc,jobjectarray strarray ){
    jstring jstr;
    jsize len = (*env)->getarraylength(env, strarray);
    char **pstr = (char **) malloc(len*sizeof(char *));
             
    int i=0;
            
    for (i=0 ; i         jstr = (*env)->getobjectarrayelement(env, strarray, i);
        pstr[i] = (char *)(*env)->getstringutfchars(env, jstr, 0);           
               
        }    
            
    hvite(len,pstr);
            
}


   代码应该很清楚，不再详细解释了。