Unreal Engine 4：学习笔记（十一）Plugins

╰+攻爆jí腚メ 2022-05-10 23:48 235阅读 0赞

如何使代码模块化，使用Plugins可能是一种比较好的方式，下面通过一个例子，讲一讲如何创建和使用Plugins。

一、创建C++工程TestPlugins:

![70][]  
从菜单中选择"Edit"->"Plugins"，会弹出如下窗口：

![70 1][]

点出“New Plgin”，在弹出的窗口中选中“Blank”，然后输入“Shape”，点出“Create Plugin”后，会创建一个名为“Shape”的plugin：

![70 2][]

工程的目录结构如下：

![70 3][]

从上图可以看到，Shape Plugin的代码目录和TestPlugin工程的基本上是一样的，都有Source文件夹和.uproject文件，Source文件夹下都有.Build.cs文件。打开“Shape.Build.cs”文件，可以看到内容如下：

// Copyright 1998-2017 Epic Games, Inc. All Rights Reserved.
    
    using UnrealBuildTool;
    
    public class Shape : ModuleRules
    {
    	public Shape(ReadOnlyTargetRules Target) : base(Target)
    	{
    		PCHUsage = ModuleRules.PCHUsageMode.UseExplicitOrSharedPCHs;
    		
    		PublicIncludePaths.AddRange(
    			new string[] {
    				"Shape/Public"
    				// ... add public include paths required here ...
    			}
    			);
    				
    		
    		PrivateIncludePaths.AddRange(
    			new string[] {
    				"Shape/Private",
    				// ... add other private include paths required here ...
    			}
    			);
    			
    		
    		PublicDependencyModuleNames.AddRange(
    			new string[]
    			{
    				"Core",
    				// ... add other public dependencies that you statically link with here ...
    			}
    			);
    			
    		
    		PrivateDependencyModuleNames.AddRange(
    			new string[]
    			{
    				"CoreUObject",
    				"Engine",
    				"Slate",
    				"SlateCore",
    				// ... add private dependencies that you statically link with here ...	
    			}
    			);
    		
    		
    		DynamicallyLoadedModuleNames.AddRange(
    			new string[]
    			{
    				// ... add any modules that your module loads dynamically here ...
    			}
    			);
    	}
    }

内容和TestPlugin.Build.cs大致相同，主要是多了对“Public”和“Private”这两个目录的包含，实际上TestPlugin也可以创建这两个目录来存放代码，只要在TestPlugin.Build.cs中中加入如下代码即可：

PublicIncludePaths.AddRange(
    	new string[] {
    		"TestPlugin/Public"
    		// ... add public include paths required here ...
    	}
    	);
    		
    
    PrivateIncludePaths.AddRange(
    	new string[] {
    		"TestPlugin/Private",
    		// ... add other private include paths required here ...
    	}
    	);

二、在Shape中添加代码：

代码目录结构：

// circle.h
    // 圆的接口类
    class SHAPE_API Circle {
    public:
    	virtual ~Circle() {};
    
    	// 接口方法：面积
    	virtual double area() = 0;
    
    
    	static Circle* create(double radius);     // 创建circle实例
    	static void destroy(Circle* circlePtr);   // 销毁circle实例
    };

// circle.cpp
    #include "circle.h"
    #include "circle_impl.h"
    
    Circle* Circle::create(double radius) {
    	Circle* circlePtr = new CircleImpl(radius);
    
    	return circlePtr;
    };
    
    void Circle::destroy(Circle* circlePtr) {
    	delete circlePtr;
    };

// circle_impl.h
    #include "circle.h"
    
    // 圆的具体实现类
    class CircleImpl : public Circle {
    
    private:
    	double radius;
    public:
    	CircleImpl(double radius);
    	double area() override;
    };

// circle_impl.cpp
    #include "circle_impl.h"
    
    #include <cmath>
    
    inline double pi() {
    	return std::atan(1) * 4;
    };
    
    CircleImpl::CircleImpl(double _radius) : radius(_radius) {
    };
    
    double CircleImpl::area() {
    	return pi() * radius * radius;
    };

中宏SHAPE\_API会自动被识别，用于把Plugin导出成dll，可能的名字为UE4Editor-Shape.dll。

三、 修改TestPlugin工程

在“TestPlugin.Build.cs”中添加“Shape”Plugin，否则编译时会找不到。

PublicDependencyModuleNames.AddRange(new string[] { "Core", "CoreUObject", "Engine", "InputCore", "Shape" });

修改ATestPluginGameModeBase：

// TestPluginGameModeBase.h
    #pragma once
    
    #include "CoreMinimal.h"
    #include "GameFramework/GameModeBase.h"
    
    #include "circle.h"
    
    #include "TestPluginGameModeBase.generated.h"
    
    /**
     * 
     */
    UCLASS()
    class TESTPLUGIN_API ATestPluginGameModeBase : public AGameModeBase
    {
    	GENERATED_BODY()
    
    private:
    	Circle* circle;
    	
    public:
    
    	ATestPluginGameModeBase();
    
    	~ATestPluginGameModeBase();
    	
    	void BeginPlay();
    };

// TestPluginGameModeBase.cpp
    
    #include "TestPluginGameModeBase.h"
    
    
    ATestPluginGameModeBase::ATestPluginGameModeBase() {
    
    	circle = Circle::create(10);
    
    	UE_LOG(LogTemp, Log, TEXT("circle.area=%f"), circle->area());
    };
    
    ATestPluginGameModeBase::~ATestPluginGameModeBase() {
    };
    
    
    void ATestPluginGameModeBase::BeginPlay() {
    	Circle::destroy(circle);
    
    	UE_LOG(LogTemp, Log, TEXT("destroy circle"));
    };

同时在UEEditor将当前Level的GameMode设置成TestPluginGameModeBase：

![70 4][]

编译后，点Play，就可以在Output Log中看到打印的日志了。

参考文档：

[https://docs.unrealengine.com/en-us/Programming/Plugins][https_docs.unrealengine.com_en-us_Programming_Plugins]

[https://wiki.unrealengine.com/An\_Introduction\_to\_UE4\_Plugins][https_wiki.unrealengine.com_An_Introduction_to_UE4_Plugins]

[70]: /images/20220511/b696548f65214e23a963cb02da180978.png
[70 1]: /images/20220511/9b520b61d3ef4d15ac79d3522be5559b.png
[70 2]: /images/20220511/1d15dc34a7124aea8858049a3bade694.png
[70 3]: /images/20220511/3afd6c15fdf34638a221b289ff87a28d.png
[70 4]: /images/20220511/c12cf28e7809400cb16cd75427928ecd.png
[https_docs.unrealengine.com_en-us_Programming_Plugins]: https://docs.unrealengine.com/en-us/Programming/Plugins
[https_wiki.unrealengine.com_An_Introduction_to_UE4_Plugins]: https://wiki.unrealengine.com/An_Introduction_to_UE4_Plugins