Android实现对c++方式调用

There are example about how Android platform call c code via NDK , which are in android-ndk-r8(version) dirctory :

/home/dengwei/android-NDK/samples

[dengwei@localhost samples]$ ls

bitmap-plasma hello-jni hello-neon native-activity native-media san-angeles two-libs

hello-gl2 module-exports native-audio native-plasma test-libstdc++

However , there is NOT a example about how to call c++ code via NDK. This article is about how android call c++ code.

The following is a modify version of hello-jni (/home/dengwei/android-NDK/samples/hello-jni), I copy it into hello-jni-cpp

You need to modify 3 files :Android.mk,hello-jni.c,com.example.hellojni.HelloJni.java

/////////////////First ,Android.mk:///////////////////////////////////////

        LOCAL_PATH := $(call my-dir)
        LOCAL_CPP_EXTENSION := .cpp
        include $(CLEAR_VARS)
        LOCAL_MODULE    := hello-jni
        LOCAL_SRC_FILES := hello-jni.cpp
        include $(BUILD_SHARED_LIBRARY)

////////////////$mv hello-jni.c hello.jni.cpp///////////////////////////////
////////////////Next , hello-jni.c：////////////////////////////////////////
#include <string.h>

        #include <jni.h>
        class myMath
        {
             public:
             static int myAdd(int x,int y){return x+y;}
        };
        extern "C"
        {
             JNIEXPORT jint JNICALL Java_com_example_hellojni_HelloJni_myAdd
                 ( JNIEnv* env,jobject thiz )
             {
                  return myMath::myAdd(10,20);
             }
        }

/////////////////Last , HelloJni.java:///////////////////////////////////////

    package com.example.hellojni;
    import android.app.Activity;
    import android.widget.TextView;
    import android.os.Bundle;
    public class HelloJni extends Activity
    {

        @Override
        public void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            System.loadLibrary("hello-jni");
            TextView  tv = new TextView(this);

            int z=myAdd();
            tv.setText(Integer.toString(z));

            setContentView(tv);
        }

        static {
            System.loadLibrary("hello-jni");
        }

        native static int myAdd();
    }

sometimes you might come to an error : could NOT find somefile.o ,what you need to do is : $ ndk-build clean

EOF