在 Eclipse 中,在 64 位 Windows 上,我试图让一个 JNI 示例正常工作,包括尝试两种处理 in/out int 参数的方法。程序运行并执行 sayHello(),但由于 modIntPtr() 的以下异常而终止:
线程“main”中的异常 java.lang.UnsatisfiedLinkError: com.aaa.bbb.ccc.HelloJNI.modIntPtr(I[I)V at com.aaa.bbb.ccc.HelloJNI.modIntPtr(Native Method) at com.aaa。 bbb.ccc.HelloJNI.main(HelloJNI.java:18)
我仔细检查了这个库,里面确实有 modIntPtr。所以我认为这一定是签名问题?在 .cpp 文件中,modIntPtr 有一个 jint,jintArray,并返回一个 void。那是(I[I)V。在 .h 文件中,签名是 (I[I)V。在 HelloJNI.java 中,我这样称呼它: new HelloJNI().modIntPtr(100, intptr); intptr 是 int[] 类型。所以这也是 (I[I)V 。
因此,如果 .dll 包含 modIntPtr 方法,我确定它是最新的,我确定程序正在与正确的 .dll 链接,这不是签名问题,还能是什么?
顺便说一句,如果我注释掉对 modIntPtr 的调用,modIntRef 确实有效。
谢谢你的帮助!
你好JNI.java:
package com.aaa.bbb.ccc;
public class HelloJNI {
static {
System.loadLibrary("com_aaa_bbb_ccc");
}
// A native method that receives nothing and returns void
private native void sayHello();
private native void modIntPtr(int delta, int[] intptr);
private native void modIntRef(int delta, IntRef intref);
public static void main(String[] args) {
int[] intptr = new int[1];
intptr[0]=42;
IntRef intref = new IntRef(24);
new HelloJNI().sayHello(); // invoke the native method
new HelloJNI().modIntPtr(100, intptr);
new HelloJNI().modIntRef(100, intref);
}
}
你好JNI.cpp
#include <jni.h>
#include <stdio.h>
#include "HelloJNI.h"
void SayHello(void)
{
printf("Hello World!\n");
return;
}
void IntRefNative(int delta, int *intptr)
{
printf("delta = %d\n",delta);
printf("intptr = %d\n",*intptr);
*intptr += delta;
printf("After mod...\n");
printf("intptr = %d\n",*intptr);
return;
}
JNIEXPORT void JNICALL Java_com_aaa_bbb_ccc_HelloJNI_sayHello(JNIEnv *env, jobject thisObj) {
SayHello();
return;
}
JNIEXPORT void JNICALL Java_com_aaa_bbb_ccc_HelloJNI_modIntPtr(JNIEnv *env, jobject thisObj, jint delta, jintArray intptr) {
jint *body = env->GetIntArrayElements(intptr, 0);
printf("delta = %d\n",delta);
printf("intptr = %d\n",intptr[0]);
body[0] += delta;
env->ReleaseIntArrayElements(intptr, body, 0);
printf("After mod...\n");
printf("intptr = %d\n",intptr[0]);
return;
}
JNIEXPORT void JNICALL Java_com_aaa_bbb_ccc_HelloJNI_modIntRef(JNIEnv *env, jobject thisObj, jint delta, jobject intref) {
jclass cls = env->GetObjectClass(intref);
jmethodID methodID = env->GetMethodID(cls, "getValue", "()I");
jint value = env->CallIntMethod(intref, methodID);
IntRefNative(delta, (int *)(&value));
methodID = env->GetMethodID(cls, "setValue", "(I)V");
env->CallVoidMethod(intref, methodID, value);
return;
}
你好JNI.h
/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class com_aaa_bbb_ccc_HelloJNI */
#ifndef _Included_com_aaa_bbb_ccc_HelloJNI
#define _Included_com_aaa_bbb_ccc_HelloJNI
#ifdef __cplusplus
extern "C" {
#endif
/*
* Class: com_aaa_bbb_ccc_HelloJNI
* Method: sayHello
* Signature: ()V
*/
JNIEXPORT void JNICALL Java_com_aaa_bbb_ccc_HelloJNI_sayHello
(JNIEnv *, jobject);
/*
* Class: com_aaa_bbb_ccc_HelloJNI
* Method: modIntPtr
* Signature: (I[I)V
*/
JNIEXPORT void JNICALL Java_com_aaa_bbb_ccc_HelloJNI_modIntPtr
(JNIEnv *, jobject, jint, jintArray);
/*
* Class: com_aaa_bbb_ccc_HelloJNI
* Method: modIntRef
* Signature: (ILcom/aaa/bbb/ccc/IntRef;)V
*/
JNIEXPORT void JNICALL Java_com_aaa_bbb_ccc_HelloJNI_modIntRef
(JNIEnv *, jobject, jint, jobject);
#ifdef __cplusplus
}
#endif
#endif
对于任何试图寻找在 java 中传递输入/输出或可变 int 参数的想法的人,我也会包含这个文件......我到处搜索了一个工作示例。
IntRef.java
package com.aaa.bbb.ccc;
public class IntRef {
private int value;
IntRef() {
value=0;
}
IntRef(int v) {
value = v;
}
/**
* Returns the integer value of this <code>IntRef</code>
*
* @return the value of the integer in native int form
*/
public int getValue() {
return value;
}
/**
* Sets the value.
*
* @param theValue The value to set
*/
public void setValue(int theValue) {
this.value = theValue;
}
}