UnitySimpleNativeLibrary

Unity native plugin

Simplest Plugin example Example code from here: https://docs.unity3d.com/Manual/PluginsForDesktop.html

Create native plugin - Windows

Follow this tutorial

Visual Studio - Create project

1. On the menu bar, choose File, New, Project.
2. In the left pane of the New Project dialog box, expand Installed, Templates, Visual C++, and then select Win32.
3. In the center pane, select Win32 Console Application.
4. Specify a name for the project (for example, SimpleNativeLibrary). Choose the OK button.
5. On the Overview page of the Win32 Application Wizard dialog box, choose the Next button.
6. On the Application Settings page, under Application type, select DLL.
7. Choose the Finish button to create the project.

Visual Studio – Strip down project

If you don't need the precompiled headers.

1. Open the project properties, in C/C++, Precompiled Headers.
2. In the options on the right, under Precompiled Header, select Not Using Precompiled Headers
3. Delete all source and headers files added automatically beside SimpleNativeLibrary.cpp
4. Put code you want to include in this library

// SimpleNativeLibrary.cpp : Defines the exported functions for the DLL application.
//

#if _MSC_VER // this is defined when compiling with Visual Studio
#define EXPORT_API __declspec(dllexport) // Visual Studio needs annotating exported functions with this
#else
#define EXPORT_API // XCode does not need annotating exported functions, so define is empty
#endif

// Link following functions C-style (required for plugins)
extern "C"
{

	// The functions we will call from Unity.
	//
	const EXPORT_API char*  PrintHello() {
		return "Hello";
	}

	int EXPORT_API PrintANumber() {
		return 5;
	}

	int EXPORT_API AddTwoIntegers(int a, int b) {
		return a + b;
	}

	float EXPORT_API AddTwoFloats(float a, float b) {
		return a + b;
	}

} // end of export C block

5. Build the library.

Create native plugin - Android

Reference guides: this, and this

1. Open Android Studio and click on New Project
2. Fill Application Name (for example SimpleNativeLibrary), Company Domain and check Include C++ Support
3. Continue like all other default android project and in the last step before click on Finish you need to set your C++ Standard! I use Toolchain Default

• if you got an exception with this message : Error:NDK not configured. Download it with SDK manager.) you should follow this steps:
• open Project Structure under File tab.
• set your NDK direction in Android NDK location and Done!

4. In the project structure, under app module, open CMakeLists.txt
5. Change the name of the library, under add_library and target_link_libraries sections. Replace native-lib to SimpleNativeLibrary
6. Go to app, src, main, cpp and paste the C++ code in the source file there.

#include <jni.h>
#include <string>

// Link following functions C-style (required for plugins)
extern "C"
{
    // The functions we will call from Unity.

    const char* PrintHello() {
        return "Hello";
    }

    int PrintANumber() {
        return 5;
    }

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

    float AddTwoFloats(float a, float b) {
        return a + b;
    }

} // end of export C block

7. Sync gradle and build the library

Use native plugin - Unity

Create project

1. Open Unity and create a new project.
2. Create folder Plugins in Assets folder. Put the compiled library in there.
3. Create a new C# script UseNativeLibrary
4. Add code to access the library in it:

using UnityEngine;
using System;
using System.Runtime.InteropServices;

public class UseNativeLibrary : MonoBehaviour {
    //Lets make our calls from the Plugin
    [DllImport("SimpleNativeLibrary")]
    private static extern int PrintANumber();

    [DllImport("SimpleNativeLibrary")]
    private static extern IntPtr PrintHello();

    [DllImport("SimpleNativeLibrary")]
    private static extern int AddTwoIntegers(int i1, int i2);

    [DllImport("SimpleNativeLibrary")]
    private static extern float AddTwoFloats(float f1, float f2);

    // Use this for initialization
    void Start()
    {
        Debug.Log(PrintANumber());
        Debug.Log(Marshal.PtrToStringAuto(PrintHello()));
        Debug.Log(AddTwoIntegers(2, 2));
        Debug.Log(AddTwoFloats(2.5F, 4F));
    }
	
	// Update is called once per frame
	void Update () {
		
	}
}

5. In your scene, add an empty GameObject and drag UseNativeLibrary script to it.
6. Press Run and you should see debug info in the console