Android 开发中 JAVA 调用 C＋＋-优快云博客

[代码] 步骤 #1:使用ANT编译项目 NativeAdd.java

 
package  org.apache;  
 

 
import  Android.util.Log;  
 

 
public  class NativeAdd {  
 
static {  
 
try {  
 
Log.i("JNI", "Trying to load libNativeAdd.so");  
 
System.loadLibrary("NativeAdd");  
 
}  
 
catch (UnsatisfiedLinkError ule) {  
 
Log.e("JNI", "WARNING: Could not load libNativeAdd.so");  
 
}  
 
}  
 

 
public static native long add(long a, long  b);  
 
    17}

[代码] 下面片断给出主activity中如何调用这个类/方法

 
public  void onClick(View view) {  
 
Log.i(LOG_TAG, "onClick");  
 
    03
 
EditText a = (EditText) findViewById(R.id.a);  
 
EditText b = (EditText) findViewById(R.id.b);  
 
EditText c = (EditText) findViewById(R.id.c);  
 
Log.i(LOG_TAG, "calling native method");  
 
long sum = NativeAdd.add( Long.parseLong(a.getText().toString()),  
 
Long.parseLong(b.getText().toString()));  
 
Log.i(LOG_TAG, "back from native method");  
 
String text = Long.toString(sum);  
 
c.setText("Native add returns = " + text.subSequence(0, text.length()));  
 
}

[代码] 步骤#2:运行下面的命令产生头文件

`1`	`javah -classpath ../../Android.jar;../bin/classes; org.apache.NativeAdd`

[代码] 新产生的头文件“(org_apache_CallNative.h”内容如下

 
    01/* DO NOT EDIT THIS FILE - it is machine generated */
 
    02#include 
 
    03/* Header for class org_apache_NativeAdd */
 
    04  
 
    05#ifndef _Included_org_apache_NativeAdd 
 
    06#define _Included_org_apache_NativeAdd 
 
    07#ifdef __cplusplus 
 
    08 extern  "C" {  
 
    09#endif 
 
    10/* 
 
    11 * Class: org_apache_NativeAdd  
 
    12 * Method: add  
 
    13 * Signature: (JJ)J  
 
    14 */ 
 
    15JNIEXPORT jlong JNICALL Java_org_apache_NativeAdd_add 
 
    16 (JNIEnv *, jclass, jlong, jlong);  
 
    17  
 
    18#ifdef __cplusplus 
 
    19} 
 
    20#endif 
 
    21#endif

[代码] 步骤#3: 编写C文件如下“org_apache_NativeAdd.c”

 
    1#include "org_apache_NativeAdd.h" 
 
    2  
 
    3JNIEXPORT jlong JNICALL Java_org_apache_NativeAdd_add 
 
    4 (JNIEnv *env, jclass c, jlong a, jlong b)  
 
    5{ 
 
    6 return a + b;  
 
    7}