android开发中JAVA调用C＋＋

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。