以UE5第三方插件库为基础，编写自己的第三方库插件，并且能够在运行时复制.dll

首先，创建一个空白的C++ 项目，创建第三方插件库。如下图所示

编译自己的.Dll 和.lib 库，打开.sln 如下图

ExampleLibrary.h 的代码如下

#if defined _WIN32 || defined _WIN64
#define EXAMPLELIBRARY_IMPORT __declspec(dllimport)
#elif defined __linux__
#define EXAMPLELIBRARY_IMPORT __attribute__((visibility("default")))
#else
#define EXAMPLELIBRARY_IMPORT
#endif

EXAMPLELIBRARY_IMPORT void ExampleLibraryFunction();
EXAMPLELIBRARY_IMPORT int AddNumbersFunction(int a,int b);

ExampleLibrary.cpp 的代码如下

#if defined _WIN32 || defined _WIN64
    #include <Windows.h>

    #define EXAMPLELIBRARY_EXPORT __declspec(dllexport)
#else
    #include <stdio.h>
#include "ExampleLibrary.h"
#endif

#ifndef EXAMPLELIBRARY_EXPORT
    #define EXAMPLELIBRARY_EXPORT
#endif

EXAMPLELIBRARY_EXPORT void ExampleLibraryFunction()
{
#if defined _WIN32 || defined _WIN64
	MessageBox(NULL, TEXT("Loaded ExampleLibrary.dll from Third Party Plugin sample."), TEXT("Third Party Plugin"), MB_OK);
#else
    printf("Loaded ExampleLibrary from Third Party Plugin sample");
#endif
}

EXAMPLELIBRARY_EXPORT int AddNumbersFunction(int a,int b)
{
    return a+b;
}

然后编译.Dll 库，配置如下

然后点击生成解决方案，编译成功后，如下图所示

创建蓝图库函数，运行时放在 插件中，如下图所示


要在WlThirdPartyLibrary.Build.cs 添加 “Engine”,“CoreUObject”，否则编译不成功
如下图

在蓝图库函数里面调用.Dll 里面得函MyBlueprintFunctionLibrary.h的代码如下

// Fill out your copyright notice in the Description page of Project Settings.

#pragma once

#include "CoreMinimal.h"
#include "Kismet/BlueprintFunctionLibrary.h"
#include "MyBlueprintFunctionLibrary.generated.h"

/**
 * 
 */
UCLASS()
class WLTHIRDPARTYLIBRARY_API UMyBlueprintFunctionLibrary : public UBlueprintFunctionLibrary
{
	GENERATED_BODY()
public:
	UFUNCTION(BlueprintCallable,Category="Function")
	static int AddNumbers(int a, int b);
};

MyBlueprintFunctionLibrary.cpp 的代码如下

// Fill out your copyright notice in the Description page of Project Settings.


#include "MyBlueprintFunctionLibrary.h"
#include "WlThirdPartyLibraryLibrary/ExampleLibrary.h"
int UMyBlueprintFunctionLibrary::AddNumbers(int a, int b)
{
	return AddNumbersFunction(a, b);
}

WlThirdPartyLibraryLibrary.Build.cs 的代码修改比较大，添加了自动复制.dll 的功能，代码如下

// Fill out your copyright notice in the Description page of Project Settings.

using System.IO;
using UnrealBuildTool;

public class WlThirdPartyLibraryLibrary : ModuleRules
{
	public WlThirdPartyLibraryLibrary(ReadOnlyTargetRules Target) : base(Target)
	{
		Type = ModuleType.External;
		PublicSystemIncludePaths.Add("$(ModuleDir)/Public");

		if (Target.Platform == UnrealTargetPlatform.Win64)
		{
			// Add the import library
			PublicAdditionalLibraries.Add(Path.Combine(ModuleDirectory, "x64", "Release", "ExampleLibrary.lib"));

			// Delay-load the DLL, so we can load it from the right place first
			PublicDelayLoadDLLs.Add("ExampleLibrary.dll");


            // Ensure that the DLL is staged along with the executable
            CopyDll(Path.Combine(ModuleDirectory, "x64", "Release", "ExampleLibrary.dll"));


        }
		else if (Target.Platform == UnrealTargetPlatform.Mac)
		{
			PublicDelayLoadDLLs.Add(Path.Combine(ModuleDirectory, "Mac", "Release", "libExampleLibrary.dylib"));
			RuntimeDependencies.Add("$(PluginDir)/Source/ThirdParty/WlThirdPartyLibraryLibrary/Mac/Release/libExampleLibrary.dylib");
		}
		else if (Target.Platform == UnrealTargetPlatform.Linux)
		{
			string ExampleSoPath = Path.Combine("$(PluginDir)", "Binaries", "ThirdParty", "WlThirdPartyLibraryLibrary", "Linux", "x86_64-unknown-linux-gnu", "libExampleLibrary.so");
			PublicAdditionalLibraries.Add(ExampleSoPath);
			PublicDelayLoadDLLs.Add(ExampleSoPath);
			RuntimeDependencies.Add(ExampleSoPath);
		}
	}
	private void CopyDll(string InFilePath)
	{
        // string TargetDirectory = Path.GetFullPath(Path.Combine(PluginDirectory, "Binaries/ThirdParty", "WlThirdPartyLibraryLibrary", "Win64"));
        string TargetDirectory = Path.GetFullPath(Path.Combine(PluginDirectory, "Binaries/ThirdParty/WlThirdPartyLibraryLibrary/Win64"));//目标文件夹的路径
        string FileName = Path.GetFileName(InFilePath);//获得文件名字
                                                       // Ensure that the DLL is staged along with the executable
        if (!Directory.Exists(TargetDirectory))//检查目标文件夹是否存在不存在则创建
        {
            Directory.CreateDirectory(TargetDirectory);
        }
        string TargetFilePath = Path.Combine(TargetDirectory, FileName);//目标文件的路径
        if (!File.Exists(TargetFilePath))
        {
            File.Copy(InFilePath, TargetFilePath, true);//复制.dll
        }
        RuntimeDependencies.Add("$(PluginDir)/Binaries/ThirdParty/WlThirdPartyLibraryLibrary/Win64/ExampleLibrary.dll");//运行时添加DLL
    }
}

还有最后一步，添加白名单WlThirdPartyLibrary.uplugin 的代码如下

{
	"FileVersion": 3,
	"Version": 1,
	"VersionName": "1.0",
	"FriendlyName": "WlThirdPartyLibrary",
	"Description": "",
	"Category": "Other",
	"CreatedBy": "",
	"CreatedByURL": "",
	"DocsURL": "",
	"MarketplaceURL": "",
	"SupportURL": "",
	"CanContainContent": true,
	"IsBetaVersion": false,
	"IsExperimentalVersion": false,
	"Installed": false,
	"Modules": [
		{
			"Name": "WlThirdPartyLibrary",
			"Type": "Runtime",
			"LoadingPhase": "Default",
			"WhitelistPlatforms": ["Win64"]
		}
	]
}