android - VS2015跨平台Android和C++

Question

我正在使用 Visual Studio 2015 进行跨平台开发。我有现有的 C++ 项目，希望 android 端调用它。我读过有关 JNI 的资料，但我改用 VS2015。

所以我可以调用 C++ 非成员函数，但是我如何调用成员函数，例如我的 SharedObject1.h 文件中的 Multiply() 下面的函数。

class SharedObject1
{
public:
    const char * getPlatformABI();
    SharedObject1();
    ~SharedObject1();

    int Multiply(int a, int b);
};

在我的 SharedObject1.cpp 文件中:

#include "SharedObject1.h"

#define LOGI(...) ((void)__android_log_print(ANDROID_LOG_INFO, "SharedObject1", __VA_ARGS__))
#define LOGW(...) ((void)__android_log_print(ANDROID_LOG_WARN, "SharedObject1", __VA_ARGS__))

extern "C" {
    /* This trivial function returns the platform ABI for which this dynamic native library is compiled.*/
    const char * SharedObject1::getPlatformABI()
    {
    #if defined(__arm__)
    #if defined(__ARM_ARCH_7A__)
    #if defined(__ARM_NEON__)
        #define ABI "armeabi-v7a/NEON"
    #else
        #define ABI "armeabi-v7a"
    #endif
    #else
        #define ABI "armeabi"
    #endif
    #elif defined(__i386__)
        #define ABI "x86"
    #else
        #define ABI "unknown"
    #endif
        LOGI("This dynamic shared library is compiled with ABI: %s", ABI);
        return "This native library is compiled with ABI: %s" ABI ".";
    }

    void SharedObject1()
    {
    }

    SharedObject1::SharedObject1()
    {
    }

    SharedObject1::~SharedObject1()
    {
    }

    int Add(int a, int b) 
    {
        return (a + b);
    }   

    int SharedObject1::Multiply(int a, int b)
    {
        return (a*b);
    }
}

所以现在我可以在将 SharedObject1.so 文件添加到下面的项目然后使用 DllImport 之后在 VS2015 中从 Android 端调用函数 Add():

using System;
using Android.App;
using Android.Content;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using System.Runtime.InteropServices;

namespace App1
{
    [Activity(Label = "App1", MainLauncher = true, Icon = "@drawable/icon")]
    public class MainActivity : Activity
    {
        int count = 1;

        [DllImport("SharedObject1.so")]
        public static extern int Add(int a, int b);

        [DllImport("SharedObject1.so")]
        public static extern int Multiply(int a, int b);

        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);

            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.Main);

            // Get our button from the layout resource,
            // and attach an event to it
            Button button = FindViewById<Button>(Resource.Id.MyButton);

            button.Click += delegate { button.Text = string.Format("{0} clicks!", count++); };

            try
            {

                EditText TV1 = FindViewById<EditText>(Resource.Id.editText1);
                int c1 = Add(4, 6);
                TV1.Text = c1.ToString();                    

                EditText TV2 = FindViewById<EditText>(Resource.Id.editText2);
                int c2 = Multiply(2, 50);
                TV2.Text = c2.ToString();  

            }
            catch (Exception Ex)
            {
                string msg = Ex.Message;
                throw;
            }
        }
    }
}

但我不知道如何调用类成员函数 Multiply()，因为它在调用 Multiply() 后总是抛出“System.EntryPointNotFoundException: Multiply”以外的异常。有人可以给我建议吗？谢谢。

------更新SharedObject1类------update(1)-----

#ifdef SHAREOBJECT_EXPORTS
    #define SHAREOBJECT_API __declspec(dllexport)
#else
    #define SHAREOBJECT_API __declspec(dllimport)
#endif

class SharedObject1
{
public:
    const char * getPlatformABI();
    SharedObject1();
    ~SharedObject1();

    int Multiply(int a, int b);
};

那么我如何在 VS2015 格式中从 android 调用此类成员？

------更新SharedObject1类------update(2)------

#ifdef SHAREOBJECT_EXPORTS
    #define SHAREOBJECT_API __declspec(dllexport)
#else
    #define SHAREOBJECT_API __declspec(dllimport)
#endif

class SharedObject1
{
public:
    const char * getPlatformABI();
    SharedObject1();
    ~SharedObject1();

    SharedObject1* getInstance()
    {
       SharedObject1* so = new SharedObject1();
       return so;
    }

    int Multiply(int a, int b);
    int Multiply_Obj(SharedObject* obj, int a, int b)
    {
        return obj->Multiply(a,b);
    }
};

Multiply_Obj() 和 getInstance() 的调用者会是什么样子？

Answer 1

保持文件 SharedObject1.h 和 SharedObject1.cpp 与上面相同，并将更新 (1) 和 (2) 拉入新项目，然后项目源文件添加包含“SharedObject1.h”，这样就应该这样做。

#include "TestMathFuncLib.h"
#include "SharedObject1.h"

#define LOGI(...) ((void)__android_log_print(ANDROID_LOG_INFO, "TestMathFuncLib", __VA_ARGS__))
#define LOGW(...) ((void)__android_log_print(ANDROID_LOG_WARN, "TestMathFuncLib", __VA_ARGS__))

extern "C" {
    /* This trivial function returns the platform ABI for which this dynamic native library is compiled.*/
    const char * TestMathFuncLib::getPlatformABI()
    {
    #if defined(__arm__)
    #if defined(__ARM_ARCH_7A__)
    #if defined(__ARM_NEON__)
        #define ABI "armeabi-v7a/NEON"
    #else
        #define ABI "armeabi-v7a"
    #endif
    #else
        #define ABI "armeabi"
    #endif
    #elif defined(__i386__)
        #define ABI "x86"
    #else
        #define ABI "unknown"
    #endif
        LOGI("This dynamic shared library is compiled with ABI: %s", ABI);
        return "This native library is compiled with ABI: %s" ABI ".";
    }

    void TestMathFuncLib()
    {
    }

    TestMathFuncLib::TestMathFuncLib()
    {
    }

    TestMathFuncLib::~TestMathFuncLib()
    {
    }

    SharedObject1* CreateTestClass()
    {
        return new SharedObject1();
    }


    void DisposeTestClass(SharedObject1* pObject)
    {
        if (pObject != NULL)
        {
            delete pObject;
            pObject = NULL;
        }
    }


    int TestMultiply(SharedObject1* pObject, int a, int b)
    {
        return pObject->Multiply(a, b);
    }
}

现在在 android 端，只需使用 DllImport 调用 CreateTestClass()，然后将该对象传递给 TestMultiply(obj, int, int);它应该工作。