android开发中JAVA调用C＋＋ _android 中 java 如何调用c lib-优快云博客

本文提供了一个在Android中使用JNI（Java Native Interface）实现Java与C/C++交互的具体示例。通过一个简单的加法运算，展示了从定义Java接口、生成本地方法头文件、编写C/C++实现代码、编译链接共享库到最终在Android应用中调用的全过程。

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来自：http://davanum.wordpress.com/2007/12/09/android-invoke-jni-based-methods-bridging-cc-and-java/

步骤 #1:使用ANT编译项目.

NativeAdd.java class

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);
}

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");

        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()));
    }

步骤#2:运行下面的命令产生头文件

javah -classpath ../../android.jar;../bin/classes; org.apache.NativeAdd

新产生的头文件“(org_apache_CallNative.h”内容如下

/* DO NOT EDIT THIS FILE - it is machine generated */
#include
/* Header for class org_apache_NativeAdd */

#ifndef _Included_org_apache_NativeAdd
#define _Included_org_apache_NativeAdd
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     org_apache_NativeAdd
 * Method:    add
 * Signature: (JJ)J
 */
JNIEXPORT jlong JNICALL Java_org_apache_NativeAdd_add
  (JNIEnv *, jclass, jlong, jlong);

#ifdef __cplusplus
}
#endif
#endif

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

#include "org_apache_NativeAdd.h"

JNIEXPORT jlong JNICALL Java_org_apache_NativeAdd_add
  (JNIEnv *env, jclass c, jlong a, jlong b)
{
    return a + b;
}

步骤#4: Please read the following article before you try the next step. 
Shared library “Hello World!” for Android

步骤#5: 编译和连接 org_apache_NativeAdd.c/org_apache_NativeAdd.h为一个共享库.

arm-none-linux-gnueabi-gcc  -I/usr/lib/jvm/java-1.5.0-sun/include -I/usr/lib/jvm/java-1.5.0-sun/include/linux  -fpic -c org_apache_NativeAdd.c
arm-none-linux-gnueabi-ld -T armelf_linux_eabi.xsc -shared -o libNativeAdd.so org_apache_NativeAdd.o
注意: armelf_linux_eabi.xsc的细节内容在步骤4中给出
步骤 #6: 复制编译文件到模拟器中. 同时安装APK程序.
adb push native/libNativeAdd.so /system/lib
adb install bin/CallNative.apk

步骤 #7:运行程序查看结果。